text:
Removable glue for LEGO models
I want to glue my 4-year-old's LEGO bricks, but I want to be able to remove the glue when he is older. What is the best glue to use that is removable and okay to use on LEGO bricks?

Standard LEGO brick are probably not the right toy if you need to glue them.  I would look at LEGO Duplo bricks, which are specifically designed for younger kids.  Then you wouldn't have to glue them.

People, people, people. Respect the lady's question and try to answer it. It's not a question about the morality of gluing bricks together, nor the wisdom of a 4-year old having LEGO bricks (which, by the way, I personally am a huge proponent of, as long as we're going there). Let's assume she's a competent adult first, and go forward from there.

Officially, LEGO Group doesn't recommend any adhesive on the toys. It can lead to corrosion or warping chemically, warping physically (the glue puts pressure on the pieces), and the removal of the adhesive also carries these risks. Plus, you'd be killing not only the the monetary value of the set, but the ability of those pieces to be active stimuli for creativity and motor skills.
The LEGO Movie clearly shows that using glue on the toys is what the villain does.

I would say low temp hot glue. I have done this for several my son really wanted to "keep". I figure one day he will be able to take it apart but it saves it from dropping and such!

I'm voting this up because it is one of only two answers so far that actually answers the question.

Your question doesn't explain why you want to glue the models for a 4 year old, so I'm going to go ahead and advocate that you don't glue and instead let your 4 year old build. 4 years old is a great time to be learning the fine motor skills, geometry, physics, colour and esthetics, not to mention creativity and storytelling. Gluing the models takes away their potential and makes Lego a blocky imitation of other toys.
Lego sells kits to 4 year olds (the Juniors line) that uses the exact same parts as the more complicated models in the other product lines. The main difference is build complexity; Lego Juniors use simple builds with few parts. With a bit of practice, your child should be able to handle the more complex construction of the other lines, which are typically set for ages 5 and up. That's only next year anyway.

There are three factors you have to consider here:  the possible chocking hazard for your child, the possible toxicity of the glue to your child, and the degree of removability of the glue.
I don't think there exist a glue that is (1) completely secure (i.e. won't allow small parts to become chocking hazards), (2) safe to be handled and possibly ingested, and (3) completely removable for future play.
If I have to recommend a glue with the safety of your child in mind, I would recommend Super-glue.  Once dry, it is non-toxic and it won't melt the plastic in the bricks.  However, it is more-or-less permanent, which is important for safe playing time (and obviously doesn't meet condition 3 above).
I strongly recommend that you consider age-appropriate building toys, such as LEGO Duplo bricks.  If you visit the LEGO Store, you can shop sets by age range to get an idea of what is available for your child.

Lego isn't exactly age-inappropriate for 4 year olds.

According to the LEGO group store, Duplo is the preferred toy for 3-4 year olds.

Duplo is suitable for 3-4 years old, but they also have the Juniors line which is for 4-7 years old. And it isn't a question of product safety; most 4 year olds are not putting the lego in their mouths. It's a question of age-appropriate themes and build complexity.

Why in the name of Sam Hill has this question become some kind of platform for child safety and anti-glueness?

As Nick says, LEGO System is probably not quite the right toy for a 4 year old. LEGO Duplo or possibly the new LEGO Juniors range would be better. LEGO obviously caution about the small parts on almost all System sets.
However, if you're looking for a temporary glue for now, then I'd probably go with a water based glue such as PVA that you'll eventually be able to soak off.
Be aware though, that this will not create as secure a bond as a permanent glue, so I would certainly advise supervising the play in case smaller elements come off.

Actually, Elmer's is in fact a PVA-based glue.

Yes, I believe Glue-All is a PVA glue, but a number of their other products aren't (for example ProBond or Kragle I mean Krazy Glue)

I'm fairly sure that the difference between Lego Juniors is build complexity, and not such much difference in choking hazards.

@Mr.ShinyandNew安宇 True, but they are aimed at 4 year olds: "LEGO® Juniors is designed to give children age 4-7 a great first experience with the LEGO® brick through iconic, fun and Easy to Build models."

You could perhaps try hot glue in some old test parts and after a few days, use rubbing alcohol to remove the joining power of the glue.
I use this method in foam planes and it separates the glue just fine.

www.le-glue.com is perfect for what you need.

Hi lee and welcome to Bricks! You're the second person to recommend Le-Glue, however as you may have seen on the first one, we're looking for longer answers than you have provided - can you expand a little on your recommendation - have you used it yourself for example? Did it do as advertised? Also, if you're affiliated with the product in any way, please let us know.

Yes, please expand a bit. I'm not a LEGO gluer, but if people want to do it, and there is a purpose-made product for this and it works well, frankly this should be the accepted answer, and the highest-voted one.

If the goal is just to make the LEGO builds sturdier, and not straight unbreakable, I'd give a thought to the various food-based "glues", like sugar syrup (will probably become sticky to the touch as well) or flour paste. Both have the benefits of being 100% food-safe and water-soluble, while still providing a bit of adhesive force.


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Any way to create a gear+chain, like for a bike?
I would like to create a LEGO bike. I can imagine how most of it would work, but i'm stuck at the chain.
I need a way for the turning pedals (at one spot) to cause the wheel (in the back) to spin with them. A design like the classic bike chain would be nice, but something else that does the job would also work.
It would be best if a solution uses standard pieces, but i do have a few special pieces.

Is this a human-size riding bike, or a smaller scale model?

A model. I sure don't have enough pieces to do a human size one. :)

It looks like LEGO sells chain and sprockets, don't know if you'd have them lying around though.
You could also try using pulleys instead. If you don't have any of the actual pulleys, take the tread off of two wheels and stretch a rubber band across, that should work too.

Good idea about the wheels. I'll try that, and then get back to you.

Perfect! Just a note, i had to use those 4-part sticks in a regular round hole, or else it wouldn't turn. I had at first used a double part stick, half round and half split, but the round part fit too tightly to spin.

I'd suggest that the Link Treads are probably a little wide for a bike, the Link Chain that Ambo100 mentions would be better, but rubber bands are easier to obtain.

The Technic Riding Cycle theme features several bikes that may be of inspiration. One particular set Moto Cross Bike (42007) uses several  3711: Technic, Link Chain parts to make a chain.

Based on Bricklink prices for the last six months, 39 chain pieces (the amount shown in the set above) would cost £4.29 (Aprox. $6.91 or €1.26).
Pulleys and rubber bands are generally more commonly found in sets but they don't tend to provide as much traction as a gear and chain.

I agree that a real gear and chain would work best, but i was looking to do it with common pieces that i already have, like in ihavnoclue's answer. Thanks anyways.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


text:
Lego EV3 doesn't respond to direct command
I tried to execute command (via bt) play tone:
play_tone = '\x0F\x00\x00\x00\x80\x00\x00\x94\x01\x81\x02\x82\xE8\x03\x82\xE8\x03'
# send commands to EV3 via bluetooth
with open('/dev/tty.EV3-SerialPort', 'w', 0) as bt:
    bt.write(play_tone)

or start program “Demo” on EV3 brick
run_demo = '\x30\x00\x00\x00\x80\x08\x00\xC0\x08\x82\x01\x00\x84\x2E\x2E\x2F\x70\x72\x6A\x73\x2F\x42\x72\x6B\x50\x72\x6F\x67\x5F\x53\x41\x56\x45\x2F\x44\x65\x6D\x6F\x2E\x72\x70\x66\x00\x60\x64\x03\x01\x60\x64\x00'

but nothing happens. No error in python script. Wireless connection status (EV3 brick display) show connected during script execution.
OS X 10.9.4, Python 2.7.5, EV3

Both of your examples are working for me. In the Bluetooth settings on the EV3, make sure "iPhone/iPad/iPod" is not checked.

Unchecking "iPhone/iPad/iPod" do the trick. Thanks a lot!

Please consider accepting David Lechner's answer if it solved your problem.

Hi, as Kramii states, it would be really beneficial for everyone if you can accept Davids answer (click the little check mark below the vote count) - David and you will both get some rep, and other people will know what worked for you :)

Vote up requires 15 reputation... which I do not have

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What adhesive can bond LEGO bricks to metal?
The Scouts are making some Christmas decorations using LEGO, and we need to stick them on to some metal stands. Could anyone please advise the best glues and process (e.g. sanding, etc.) to join bricks to metal. Many thanks.

See also this question on Gluing baseplates to wood. The slight difference here is that neither of the surfaces are porous - (props to @Mr.ShinyandNew安宇 for the reminder).

Have you considered screwing your decorations to the metal stand, using Technic brick holes to pass the screws? If done properly no harm is done to the bricks, and you will not fear a bad glue joint!

A similar question recently asked about gluing baseplates to a wooden table, and the technic plates with holes were suggested; that would give the same effect as this brick but in the vertical orientation.

I'm always hesitant to recommend gluing LEGO as it is so much against the spirit of LEGO. Have you considered using the magnet bricks? They come in several regular LEGO brick sizes, and they stick to metal surfaces just fine.
If you must use glue, most glues will readily stick to the plastic, so that is no problem. What you need to check is what glues work well for metal. Personally I would go over to a home improvement store, hobby shop or craft store and ask, as there will be different glues available in different regions/countries.

Many thanks for all your help and ideas.
We have experimented with gorilla glue and a couple of others but settled on two part Araldite Rapid, which doesn't take long to set.  As they are tree decorations that we are selling to raise funds to build a new building (our old one is rotting away!) they needed to be fairly robust.
Sorry that we are sticking Lego forever, but for every brick we sell we get real bricks in return for our new building!

It's a self answer - Amanda tried a couple of suggestions, but found that Araldite Rapid to be the best solution to the problem ;)

Depending on how sturdy you need it, then a lot of glues will work.  In other words, if this is just going to sit on a shelf, you really don't need tremendous adhesive power.
In this case, I would recommend something like JB Weld or Gorilla Glue.  However, make sure you properly prepare both surfaces by roughing them up a bit and cleaning them.
If you need something stronger, I'd look at two-part epoxies that are used in automotive repair.  These are specifically formulated to bond metal to plastic.  Fusor 116 is one such product.
LEGO bricks are made from ABS, so any glue that will bind ABS to metal will work.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What are these bricks with filled interior and holes/tubes going through?
I recently bought at haul and found a bunch of these regular sized bricks. Can anyone identify the for me?
They are 2x4 bricks, but with holes in the side of the bricks:

From: https://i.stack.imgur.com/Atc7p.jpg
It says Lego on the stud, but no part numbers are to be found anywhere, so I guess they are old.
Any help is appreciated.

They were used until 1990 for trains, the holes are there to stick in the wheels.
This is the part: http://www.bricklink.com/catalogItem.asp?P=7049b
And these (for example) were the wheels: http://www.bricklink.com/catalogItem.asp?P=wheel2a

you mean the 1970's, right ?

Makes sense as there was also wheels and tracks in the haul. Thanks a lot.

You're welcome.
@Stephane, no I mean the 1990's, it was still in basic building sets in the late 1980's and the early 1990's.

oh, I remember them in the early 80's.

@Laz75 According to the BL page you posted, it seems most of these kits with these parts were released in the 70s, with only a tiny handful of kits in the 90s having these in them.

@Mr.ShinyandNew安宇 you're absolutely right, that's why I wrote "until"!
The white ones though, the ones in the picture, are actually only from the 1960s amd 1970s, you're right.


text:
Is it possible to edit a MyBlock input parameter value?
I have created MyBlocks but want to change the input parameter to negative. Is this possible or must all the MyBlocks be re-written?

It is possible now (since version 1.3.0) by pressing the button at the upper left corner of the block:

It is not possible to modify the properties of myBlock in the current version of EV3 SW.
It is possible by tampering the block source files:

create a copy of your *.ev3. Just in case
rename *.ev3 to *.zip
extract all files from the zip
edit files as needed
move changed files back into zip (Under Windows drag and drop to zip)
rename *.zip to *.ev3

I successfully used this to change the icons for MyBlocks. Icons file should be here: C:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS EV3 Home Edition\Resources\MyBlocks\images
If you change the parameters, you will have to change all programs that use the MyBlock because the definition has changed.
I have tried it with success, having a backup is a must, you can easily corrupt your project files. I was able to modify the icon of parameter or myblock, rename the parameter, change the order of parameters, change the default values, add a new parameter. It is also possible to change the parameter type or delete the parameter, the lab sw removes existing wires correctly.
I would not tamper the files for some simple block, but for more complex block it could be worth. Let's hope some sw update will provide this function later, if it could be done manually, i see no reason why it is not implemented.

If you need to change something that is setup in the "My Block Builder" dialog box like the default value or min and max values for a slider, then yes, you need to create a new My Block. This is easy though. Just select everything in the existing My Block except for the Input Parameter block, the Output Parameter block and the Start block and then select Tools > My Block Builder to create a new (identical) block.
Another option would be to add a Math block inside of your My Block that multiplies the input parameter by -1 to make it negative.

If only we knew the developers' thoughts perhaps they intentionally made it hard to change MyBlocks in order to support some programming paradigm for kids (according to their opinion).
What I do is:

Always put the variables into the block while their values come from outside constants. Never cross commands boundaries with wires. Put all the variables inside the block, next to their use, no matter how many times you use them. The order of the block's wires is usually the order of their first use inside the block.
Make a copy of the program you want to routine
Make a block of the copy:

Give the block a very clear name
Put no effort in any other features until you test the block to work 100%.

For the final block version: just create it anew while still retaining the original commands, in a different file.

I know it is few years late but I just looked for this and then found an alternative/workaround. There is no way to edit a custom block, but one can select all of it (except inputs and outputs) and create a brand new block from it, then delete the original.
Too bad there is no direct way for this.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Gearing down a PF XL
I'm looking for the best way to gear down a Power Function XL.
I need to achieve a very slow output RPM (less than 1-2 RPM). I've tried a 625:1 gear (trough 40:8 gear). Can someone link to a well done gearbox like that? Moreover, how I can make an axle more resistant at high torque (I've tried with brick round 2x2).

Do you mean less than 1-2 RPM?  As written, you're indicating greater than 1-2 RPM.

Yeah, I mean <1-2RPM (or around).

The XL motor runs at approximately 220 RPM.  Therefore, the following gearbox from the ELEC 201 class LEGO Design module from Rice should be sufficient:

You can use a worm gear for a compact, high ratio gearbox. By putting a worm gear on the motor shaft and using it to drive a 24 tooth gear you can achieve a 24:1 reduction.

For high torque applications you could use multiple parallel axles held together by gears or wheel hubs.

Sadly, a 24:1 doesn't resolve my problem. Maybe i can add some other gear using worm gear as the input.

Then by using two of these assemblies you can achieve 576:1 reduction. Or if that is too much, you can get another gear either before or after this setup for an additional 2:1 or 3:1 reduction.


text:
NXT brick not executing programs correctly
I have an issue that I am hoping someone might be able to resolve:
We're using Mindstorms in the classroom as part of a STEM program, and have one NXT brick that won't execute programs correctly. The program is a simple move/turn/move program and the program works on other bricks.
It will move forward and seems to attempt the turn but then just stops.
Working programs from other groups also don't execute correctly on this particular brick so we eliminated a programming error.
We have tried soft reset, hard reset, and updated the firmware all with no effect.
I'm hoping it doesn't mean we have one totally useless robot. Any help is appreciated!

Does it behave in a similar way if you use different ports for the motors?

Without more information, it seems like one of the following is to blame:  bad ports, bad motors/devices, bad wires, bad power, or bad NXT.  The easiest way to test these would be to create simple programs and test things one at a time.

There are a few options for the cause of the error. It could be at the microprocessor level, meaning that the execution of the program is wrong, or it could be at the motor driver port, meaning that the NXT tries to drive the motor attached to the specific port but can't due to some electrical failure.
The first option can be eliminated by using other forms of output (e.g. screen) instead or along with the motors, the second can be analyzed by swapping motor ports and testing them individually.
However, in any case you probably won't be able to repair it yourself, so you should contact Lego instead if the existence of the error is certain.


text:
How many ways can six 8-peg lego blocks of six different colors be combined?
I have seen the number quoted as > 650 billion. The quote is from a Danish mathematician, Soren Ehlers. Intuitively, this does not seem correct to me. Any mathematicians/statisticians out there who can help either verify the huge number, or give me a correct number?

This might be a question better suited for Stats.SE or Math.SE.

To expand on Zhaph's answer, I'm assuming that you have a fixed set of six colors, and each block is one color.
If that's the case, this is a simple combination problem on top of the orientation problem.  Since there are six colors and six bricks, there are 6! ways to assign those six colors to the six bricks, or 720 ways.
Now, we apply this combination to our orientation, and get:

915,103,765 orientations x 720 color combination/orientation = 658,874,710,800 combinations

So it's true! Thank you for your verifications, Zaph and Nick. Very much appreciated. FYI, I'm using this to explain the complexity in large data sets. i.e. if six Lego blocks can connect in this many combinations, how many ways can six humans connect? Traditional Taylorist management theory says one! That leaves lots of possibilities unexplored.

@Bonifer people connect simultaneously in much simpler ways than Lego bricks (Sam knows Bob or not) and in much more complex ways (Sam has heard that Bob is not very nice, but from someone Sam thinks is unreliable). There's not a good match to the Lego "one stud to the left" relationship modelling.

This number is probably too high. Some arrangements will be symmetrical such that switching the brick colours doesn't give a new creation, just a rotation of the previous one.

@Mr.ShinyandNew安宇 is right.  It's difficult to guess how many different brick configurations are radially symmetric.  However, it's safe to assume that the number is fairly low, because the only possible configuration would have to be 90 and/or 180 degrees rotationally symmetric.  90 degree symmetric sets would have 1/4 as many combinations, and 180 degree symmetric sets would have 1/2 as many combinations.

I'm not sure what the rules are around the colours, however from the LEGO Facts page:

Take six eight-stud LEGO bricks (2x4) – how many ways can they be combined?
With the aid of computers, the exact number of combinations has been calculated as 915,103,765!
Just so you know, two eight-stud LEGO bricks can be combined in 24 different ways and three eight-stud LEGO bricks in 1,060 ways.

This is probably based on the work done here.
The colour combinations would therefore be higher than that - but you'd need to be avoiding duplicate combinations.


text:
What kind of design is comparable to these programming concepts?
I understand this may sound like a weird question, but bear with me here, OK?
I'm getting ready to teach some kids introductory computer programming. We're going to use Scratch, a drag-and-drop "brick-based" language designed by MIT.
Now, scripts in Scratch are comparable to LEGO structures. Each script needs a base, and pieces to build it up. So far, so good.
However, scripts can also contain conditionals and loops, both of which accept a sub-structure.
I would like to show my students a LEGO structure that is comparable to a Scratch script. How could i do something like conditionals and loops?

A conditional can perhaps be represented by a door that can be blocked from the other side, or maybe two doors, of which only one is blocked via a sliding brick.
As for loops, I would represent them as conditionals with counters, by blocking a door with a set number of bricks and removing one brick per iteration. If you'd rather count upwards, then a fixed size hole can be filled with bricks gradually.
These analogies were made to the "minifig walking through a set of corridors - the program" analogy, but we could surely find solutions for axles and gears or even pneumatics if you were thinking along those lines.

I was thinking more along the lines of "this building is like a script", but your ideas seem to work with that as well.

@Scimonster If the answer was useful for you, please consider accepting it, unless there is some information you still wait for, in which case I'll be happy to amend it.

I'm just waiting to verify that this works. I will be holding the class next week, and will try it out then.

In the end the kids were able to understand without the LEGOs, but you had a good method anyways. I might use it next time. :)

Based on the image on the Scratch home page, I would simply wrap the substructure in a single color, which represents the loop.
For example:
 ______
|_Loop_|__
|__|__s1__|
|__|__s2__|
|__|__s3__|
|______|

If that makes sense.

While that indeed works visually, i'm not sure it conveys the message of a loop.


text:
Identifying Lego kits from unopened bags for library
I'm a librarian and we recently received one of the Junior Maker Lego kits that LEGO distributed to 15 libraries in each state. It's a wonderful kit and includes a lot of basic blocks along with many numbered bags that clearly go to sets. However, none of the set information is included, nor can I find it online. Some I know are from the Chima theme based on the minifigs. I'm happy to upload pics if you all wouldn't mind helping, but there's about 20 different ones. Is there an easier way to do it?

Without pictures, there's not really a whole lot to go on.

I did some research on the program, and there's a lot of material on the ALSC website, include, for example, this toolkit:  http://www.ala.org/alsc/sites/ala.org.alsc/files/content/Juniors%20Librarian%20Toolkit_September_FINAL.pdf

I suspect that the intention is that the exact sets don't matter, and they may even vary between kits. Because those pieces are going to end up really mixed very quickly, so either you're going to spend a lot of time policing and sorting, or you'll end up with one big pile of pieces. Personally I would resign myself to that now and move on...

I think @Mσᶎ pretty much has the right idea. creativity gets messy and there's little point in attempting to catalog the exact element mix.

While I agree that Mσᶎ is probably right, there can be some value in having some instructions that can be made from the supplied kits so that the kids have something they can start from.

If you really want to know, I would suggest identifying the most unusual part in a bag, then  using that part, search for what sets it has appeared in recently.  Each piece usually has a small number printed on it.  Use this part number on bricklink, or peeron to search for the part, and then click the link that shows you what sets it has appeared in.
Alternatively, take a picture of the bag and post it to the AFOLs of Facebook group and you'll probably have an answer in 5 minutes or less.


text:
LEGO TECHNIC CyberMaster Software
I come again to ask a favor. Can someone share the installation CD in English of LT 8482 CyberMaster or where can I download the software in English??

About 10 mins on Google didn't turn up any place to download the software, but you can always buy a CD from one of the sellers on Bricklink:
http://www.bricklink.com/search.asp?itemID=43378
You might be able to get one of them to upload the CD


text:
Lego EV3 - sending direct commands over RFCOMM Channel (Objective-C, Xcode)
I successfully open RFCOMM Channel to Lego EV3 brick with code:
IOBluetoothDevice *device = [IOBluetoothDevice deviceWithAddressString:@"xxxxxxxxxxxx"];
IOBluetoothRFCOMMChannel *rfCommChannel;
IOBluetoothSDPUUID *sppServiceUUID = [IOBluetoothSDPUUID uuid16:kBluetoothSDPUUID16ServiceClassSerialPort];

IOBluetoothSDPServiceRecord *sppServiceRecord = [device getServiceRecordForUUID:sppServiceUUID];

if ( sppServiceRecord == nil )
{
    NSLog( @"Error - no spp service in selected device." );
}

UInt8   rfcommChannelID;
if ( [sppServiceRecord getRFCOMMChannelID:&rfcommChannelID] != kIOReturnSuccess )
{
    NSLog( @"Error - no spp service in selected device." );
}

if ( ( [device openRFCOMMChannelAsync:&rfCommChannel withChannelID:rfcommChannelID delegate:d] != kIOReturnSuccess ) && ( rfCommChannel != nil ) )
{
    NSLog( @"Error - open sequence failed." );
}

Now I wish to send direct command:
unsigned char play_tone[] = {0x0F,0x00,0x00,0x00,0x80,0x00,0x00,0x94,0x01,0x81,0x02,0x82,0xE8,0x03,0x82,0xE8,0x03};

over RFCOMM Channel using class IOBluetoothRFCOMMChannel method:
- (IOReturn)writeSync:(void *)data length:(UInt16)length

I tried to do send it using different ways but none of them worked. How should I do it properly?

Does writeSync (or anything else) return an error? Can you post a link to the entire XCode project?

Link to git repository: https://github.com/mclientx/direct-commands-over-bluetooth.
writeSync returns kIOReturnSuccess. Delegates rfcommChannelOpenComplete, rfcommChannelQueueSpaceAvailable and rfcommChannelFlowControlChanged are invoked but not rfcommChannelWriteComplete.

I have found solution. I create category NSString+NSStringHexToByte:
NSString+NSStringHexToBytes.h
#import <Foundation/Foundation.h>

@interface NSString (NSStringHexToBytes)
+ (NSData *)dataWithString:(NSString *)string;
@end

NSString+NSStringHexToBytes.m
#import "NSString+NSStringHexToBytes.h"

@implementation NSString (NSStringHexToBytes)

+ (NSData *)dataWithString:(NSString *)string
{
    string = [string stringByReplacingOccurrencesOfString:@"0x" withString:@""];

    NSCharacterSet *notAllowedCharacters = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefABCDEF1234567890"] invertedSet];
    string = [[string componentsSeparatedByCharactersInSet:notAllowedCharacters] componentsJoinedByString:@""];

    const char *cString = [string cStringUsingEncoding:NSASCIIStringEncoding];
    const char *idx = cString;
    unsigned char result[[string length] / 2];
    size_t count = 0;

    for(count = 0; count < sizeof(result)/sizeof(result[0]); count++)
    {
        sscanf(idx, "%2hhx", &result[count]);
        idx += 2 * sizeof(char);
    }

    return [[NSData alloc] initWithBytes:result length:sizeof(result)];
}

and now:
NSString* playTone= @"0f0000008000009401810282e80382e803";
NSData* data = [NSString dataWithString:playTone];
[self sendMessage:data toChannel:rfcommChannel];

where sendMessage is:
-(void)sendMessage:(NSData*)data toChannel:(IOBluetoothRFCOMMChannel*)rfcommChannel
{
    [rfcommChannel writeSync:(void*)data.bytes length:data.length];
}


text:
Unlimited engine option does not work
I  work in a school and all my Lego NXT bricks have the same problem. Unlimited choice in the activation time engine does not work. The other functions (rotation, and second degree) are going well. So I can use my probes and so I am very limited in the tasks to be performed.
I've done these actions, but without success:

Reset On my brick
Update Bricks
Update The program to version 1.31
Contact My representative

EV3 software?  or NXT?

Are you able to summarise your program or post a picture of it?

You need to ensure that your program has a way to stay alive (wait block, wait for sensor, etc...), otherwise as soon as the program ends all motors are stopped.

Looks like a comment to me.


text:
Is it possible to create your own wheel?
After my other question, i pretty much have a bicycle design all planned. My problem now is with wheels.
None of my LEGO wheels are big enough to work on a bike. And, the biggest ones are all pretty fat.
I was wondering if it would be possible to simulate my own wheels, that i could then attach to a LEGO creation.
It doesn't have to be made out of only LEGOs; i'm open to other building toys and materials as well.

You can always brick-build a wheel.  The curved slope pieces can closely approximate a circle.
For example, 12 4x1 curved slopes gives a circle with a radius of 160 LDUs (8 studs).
For more information on brick-built wheels, I suggest you refer to the "Brick Built LEGO Wheels Book":

http://www.ultimate-design.org/2014/05/unofficial-free-brick-built-lego-wheels.html


text:
Can anyone identify these Bionicle sets?
Can anyone identify these Lego pieces? They were given to us in a bin of toys, and we cannot identify them. We know they're Lego, and have a 2002 date on them.

Those appear to be Bionicle figures, a theme that was active from 2001 to 2009 (and making a comeback in 2015, I hear). The line focused on buildable "action figures" (aka "constraction figures").
See here: http://brickset.com/sets/theme-Bionicle

The yellow one is the Glatorian-era Mata Nui, the red one with the staff is a Toa Nuva-era Rahkshi (Turahk, to be specific), and the green spider-thing is a Toa Hordika-era Visorak (Keelerak) that has been placed upside-down.
The other four are Metru Nui Matoran, without their masks; the lighting makes it hard to tell what elements they correspond to, but the ice one appears to have the wrong head.
Turahk: http://brickset.com/sets/8592-1
Keelerak: http://brickset.com/sets/8746-1/Visorak-Keelerak
Can't post other links due to reputation; sorry about that.


text:
How do I make my logo/mascot into a custom LEGO model?
I operate an Indoor Playground & Cafe and would love to find out how to make my mascot/logo into a 4' custom LEGO sculpture.  Any assistance appreciated!
A bit of looking indicates that LDD will generate instructions and parts list but I am not competent with this type of CAD software.  Additionally, LEGO no longer 'makes my model'.

The cheapest way to go about doing this is to design it yourself, like you said, using one of the LEGO cad softwares (LEGO Digital Designer, LDraw, MLCAD, etc.).  Then, buy the pieces and build it.  However, that takes a lot of time, and unless you are experienced, may not turn out so good.
The easiest (but also likely expensive) way to do this is to hire a LEGO certified professional.  The LEGO certified professionals are LEGO enthusiasts who have turned that passion into a business, and are officially recognized by LEGO for their work and skill.
http://aboutus.lego.com/en-us/lego-group/programs-and-visits/lego-certified-professionals
I would contact a certified professional and see how much they need to design and build your logo.

A big Scratch Cat was designed and creating in the following way, according to a Scratch Team member:

The Lego company very generously helped us create a version of the Scratch cat made of Lego. My friend Duks and I made a 3D model using Rhino, and we sent it to Lego for fabrication. A few months later we got a big crate containing... this!

Source: http://scratch.mit.edu/projects/1017438/
This seems to be a successful mix of the two methods from Nick's answer.


text:
Can I build a faster LEGO train motor?
I was going over LEGO Power Functions train motors, and I was not satisfied with the speed. Speed seven is fast enough to derail the train on the curve, but not fast enough realistically. I am thinking that if I open the motor and put in bigger cog wheels, it will hopefully make my train go fast enough (I'm trying to get at least 10 mph.) Will this work? Where can I get bigger cog wheels?

10 mph means that train is going really fast. In scale, that's approximately 380 mph!!!

Yes, but I like to think of it as 574.8 km/h (just like the real TGV!)

Even if speeding up the motor were possible (which I'm ambivalent on), I doubt that you'd be able to use it at that speed on Lego track. Once again, issues of scale come back to bite you. A small .1mm lip would be the equivalent of almost 4cm lip in real life. Which is well outside the rail specs and would put the train at high risk for detailing. Though Lego has very tight tolerance, I don't think they are tight enough for that speed.

10mph is nearly 4.5 metres / second. You're going to need a lot of track...

Nick2253: It has been done before with a 9v motor: https://www.youtube.com/watch?v=5DZnSroTRLA. I was just trying to figure out how I can do the same with a PF motor.

You also need to remember that there are really two scales at work with LEGO trains: One is the true "Minifigure" scale, and the other is the actual train build scale: Most real world trains are wide enough to fit two sets of two seats in a carriage (four people and an aisle), while LEGO trains barely manage 1 seat wide. The gauge of the track does not match the scale of the people.

@TaylorGarrett That train isn't going even remotely close to 10mph.  I don't think it's going faster that 5mph, since it looks like I could easily out-jog that train.

I think you would say otherwise after watching this video: https://www.youtube.com/watch?v=8-h-BKMfpGU

Mathematically, the largest driver wheel you can buy for LEGO is Big Ben's XL driver, with a diameter of 36.8mm.  To reach 10 mph, that wheel will have to spin:
36.8 mm diameter -> 115.6 mm circumference -> 7.2 x 10^-5 mi/revolution -> 2320 RPM (!!)
This means that you have to gear up a motor to run at 2320 RPM.  An XL PF motor with no load spins at about 220 RPM.  I just don't think that's going to happen.
And if your goal is to use the smaller wheels, there's no way to accomplish what you want with LEGO.
Don't forget, the TGV (and other high speed trains) are incredibly complex and well engineered machines.  It requires a specific track layout, curve radius, rail width tolerance, surface roughness tolerance, and we haven't even reached the train itself.
Honestly, accomplishing a scale-equivalent speed using only LEGO bricks would lead to a revolution in transportation design, because if you can do it with LEGO at L-gauge without blowing up, you could easily do it with steel, plastics, and composites at people-scale.

Thank you for your answer. I already have the curve radius problem that you speak of completely eliminated using this technique:  http://www.holgermatthes.de/bricks/en/smooth-curves.php.

While that may be "smooth" from our perspective, that is incredibly tough from the trains perspective. The gaps and angles there are simply unacceptable for a train moving at 10 mph

if someone want to check the computation, or play with variables: http://www.wolframalpha.com/input/?i=%2810miles+%2F+%2836.8mm++PI%29%29%2F60

The stalling torque on an XL PF motor is 40 N.cm so to get 10x the speed, it would be 1/10 the torque, or 4 N.cm, or 0.04 Nm. Without knowing the mass of the wheel its hard to go further with those calculations though. In a perfectly efficient frictionless world of course.

The PF XL motor is a bad choice for a direct RPM comparison, as it's more built for axle-bending torque instead of pure speed (yes, you can use gears to change the two, but you aren't doing so in your comparison) - a faster motor such as the 2838 (old,  9v motor) reaches 4k RPM, the buggy motor reaches 1700 RPM, which is much more in-line with the 2k RPM of the train motors themselves. Even the E-motor is close to 800 RPM and makes more sense in a comparison if you want a fast motor RPM.

10 mph (16km/h) is a crazy speed at that scale [citation needed]. Chances are quite high that your car will derail even on straight lines.
Now, is it possible to reach that speed using lego motors and lego pieces ? I'd say no, but I think you can get quite fast, in the magnitude of 10-12 km/h (6-7.5mph).
As stated in another answer, using the bigger train wheels available, you need to reach 1740RPM loaded (for a 7.5mph target).

Note: all electrical motor facts are from: http://www.philohome.com/motors/motorcomp.htm

The first option coming to my mind is using a (couple of) pull-back motors (http://brickset.com/parts/6024100)

The torque is quite high, the rotation speed is crazy, but:

it'll totally unwind in about 8-10 meters, going freewheel
it'll probably slip at startup
it's not RC

The second option is using the PF train motor, which rotate at ~1900RPM unloaded. You can get extra power (up to 1.9W) by powering it with 12V batteries (at your own risks). Changing the gearing on this one won't get you far. Sure you'll get higher unloaded RPM, but your performances loaded will be really poor.
I've seen cars using 2 of those reach 12km/h, so why not trains ?
Still not fast enough ? Try the mighty RC Buggy motor (http://brickset.com/parts/4177239)

You will have to gear it up a bit (unloaded RPM is 1700), probably at 2x. You might even have to power-it up to 10.5V, but I've seen technic cars reaching 12km/h using this motor, so why not trains ?
But it's already time to slow down, you're approaching the first curve.

The reason those cars can reach 12km/h is because they are ridiculously overbuilt.  Imagine a car that looked like that in real life, and you'd get something like a dune buggy with 2-3 ft wide wheels.  However, it would be really hard to reach that speed with a scale-accurate vehicle because you've got relatively imprecise (in-scale) LEGO tolerances to deal with.

Aside from the mechanical enhancement, you could also apply more electrical power to the motor. Some LUGs achieve record-breaking train speed by doing just that, although they usually use custom rails as well as transformers.
Of course, overpowering motors isn't usually recommended; and for a PF one you'll have the issue of embedding a larger battery; but considering the PF motor isn't very expensive and may be able to sustain excessive power quite gracefully, it might be worth a try.
Other than that, yes, using other motors than the train one might be a good solution. Even with regular trains, you can build a mock motor which can then be driven by another PF motor in the cabin. Not sure it would sustain high speeds though.

Thanks for the suggestion! This really helps. I plan on purchasing an XL motor and some gears (like the ones in the picture in the link that you posted) and get my train going! Thank you! You have gave the answer that I was looking for! Installing this in my train will be not a problem at all.

Also notice their special custom tracks and the way curves are made bent to counterbalance centrifugal forces.
Also, for having witnessed it, a train crash at those speeds is spectacular, although maybe not so for the one who owns the train.

If the original train motor is not fast enough, you could build your own engine using normal PF motors and use gearing that is suitable for your needs. Then drive your train via stand-alone train wheels:

Yes, this train is not going at 10mph. The 12 kph from that video is about 6-7 mph. Closer to 5. You could try rewinding the coils in the motors of the wheel system as to increase the rpm of the motor.
Look this up if you are unclear on anything.
Also, try switching out the motor for that of higher RPM

Simple way is to buy mini faster engine on ebay and install it in, like 10000rpm one or 25000rpm one would then it would increase speed but the issue is quite complicated to install in but can be done then if rpm increase, speed would be about the same but don't think it would hold on the track you would need to redesign whole train add weight and then different wheels etc...

Hi Nuero, you seem to have a quite concrete suggestion here. Do you, per chance, have any experience with this kind of solution, i.e. have you done that yourself? If so, I'm sure OP and the community would appreciate if you shared your insights, results, potential pitfalls and recommendations.


text:
How to close color Sensor properly?
I want to get data from the color sensor with Bluetooth. I can get data but when the program terminates, the color sensor dose not close even though I call function close() on the color sensor. The following code is what I did with EV3 Bluetooth connection.
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
ev3.setDefault();
Keys keys1 = ev3.getKeys();
color_sensor = new EV3ColorSensor(SensorPort.S2);

do{
  color_id = color_sensor.getColorID();
  System.out.println("Here is color id: "+color_id);
  Delay.msDelay();
  keys1.waitForAnyPress();
}while(keys.getButtons()!=Keys.ID_ESCAPE);

color_sensor.close();

And it throws the following exceptions:
Exception in thread "main" lejos.hardware.DeviceException: unable to open port
at lejos.internal.ev3.EV3Port.open(Unknown Source)
at lejos.hardware.motor.BaseRegulatedMotor.<init>(Unknown Source)
at lejos.hardware.motor.EV3LargeRegulatedMotor.<init>(Unknown Source)
at lejos.remote.ev3.RMIRemoteRegulatedMotor.<init>(Unknown Source)
at lejos.remote.ev3.RMIRemoteEV3.createRegulatedMotor(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at com.sun.proxy.$Proxy0.createRegulatedMotor(Unknown Source)
at lejos.remote.ev3.RemoteEV3.createRegulatedMotor(Unknown Source)
at test_bluetooth.Bluetooth.main(Bluetooth.java:186)

I am not sure that color sensor is really closed because when I run the program for the second time it yields the exception that it's unable to open the port of that color sensor. However, after I restart the brick, it works fine for the first time the program is run, then I need to restart again to use that color sensor port. Can anyone tell me how to properly close the color sensor?

I using Java and moreover, I notice that when I connect my EV3 by Bluetooth with my Laptop the motor is not rotating smoothly like when I write the program in compile it directly with Brick itself. Can you explain it to me?

Also - where are you seeing the error coming from - is it when you try and instantiate the EV3ColorSensor or when you instantiate the RemoteEV3? Both of these appear to be able to throw the error you're seeing. One other thing: according to this thread it might be more efficient to use the createSampleProvider method when dealing with remote bricks and sensors.

There is no error in the first run but when I run it the second time it throws the error that it is unable to open the port. I think because I cannot close the color sensor.

Yes, I got that part - I'm really asking if there's any more information on the error about where in your codebase the exception is being thrown - there are two possible lines that can throw that - in your pasted code these are lines 1 and 4 - I was hoping there would be stack trace (especially if this is happening on your Laptop rather than on the Brick).

I post that exceptions but can you help me with one more problem? I use RMIRegulatedMotor but it is not smoothly rotating the motor. Can I use RegulatedMotor with remote control?

Hmm, looking at your stack trace, it seems to be throwing at RemoteEV3.createRegulatedMotor rather than on your EV3ColorSensor - this doesn't appear to be called by the RemoteEV3 constructor, but something in your main block?

You mean I don't close the motor sensor properly?

I got the problem, I think I don't close the motor sensor that lead to above problem. Thank Zhaph For pointing out the problem.

Looking at the stack trace in the exception you've posted, the error seems to be coming from a call to RemoteEV3.createRegulatedMotor:
at lejos.remote.ev3.RemoteEV3.createRegulatedMotor(Unknown Source)
at test_bluetooth.Bluetooth.main(Bluetooth.java:186)

After that, it's just going through the motions to try and open a port on a remote device...
From looking at the LeJOS source, that method isn't called by the main RemoteEV3 constructor when setting up the ports, so it is probably something you're calling in your main block.
Both Sensors and Motors need to be closed.
As a point of note, it's recommended that instead of connecting to the remote sensors directly as you're doing there, you instead use the createSampleProvider method:
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
RMISampleProvider color_sensor = ev3.createSampleProvider("S2",
               "lejos.hardware.sensor.EV3ColorSensor", "Color ID");
float[] color_id= new float[1];
color_sensor.fetchSample(color_id,0);

It is apparently more efficient because instead of running the sensor driver on the PC and sending requests to the remote EV3 you're creating the sensor driver on the remote EV3 and sending the samples to the PC.


text:
How can I prevent my train from derailing?
I have motorized the Constitution Chase train by putting a PF train motor into the coal car. I disassembled the rest of the cars, down to the car bed, and let my kids build whatever train cars they want. This, plus a few cars from a City train let me run a train with the engine (which is a dummy), the motorized coal car, two short cars with fixed wheel trucks and two long cars with turning wheel trucks.
The problem is that sometimes this train works really well and other times it just cannot stay on the tracks at all.
The tracks are laid out on a carpeted floor, but I always put the train in the same place and it usually runs fine. But today's layout was just unworkable and I had to disassemble it and start over. The second layout works and I'm not sure what the difference is. The train rolls along and then whoops, the front wheels of the engine are turned, and the whole things falls down.
The layout itself is designed to withstand the perturbations of the train. This is accomplished by using a single piece of flex track every 1/4 turn and wherever there is a switch. This helps keep the track from shaking loose, as nothing is typically attached anywhere, except for the snap-together action of the track pieces.
Today I tried to settle down a particularly bad stretch of track by mounting it on some 10x20 bricks but that didn't really solve the problems.
Is there a way to reliably run the train on a carpet base? Or even to just improve the reliability over what I have now, which seems somewhat random.

I'm no train head, but I suspect the best solution is a piece of plywood big enough to accommodate your layout.

So, is the problem that the train is coming off the track, or the track is coming apart?  I'm not sure what you mean by "...the whole things falls down."  Also, what happens if you don't have the flex track?

:) Yes, I'm sure if I were to build on a table or wooden floor or some other more structurally sound surface it'd work better. But I lack the space for such a surface, so I was hoping for a bricks-only solution.

@Nick2253 What happens is that the front wheels of the locomotive derail, and on that locomotive they are constructed in such a way that the entire wheel truck can turn and sway significantly. Once the wheels are off, it's a matter of seconds before the locomotive falls over. The track stays together, primarily because it has so many flex pieces here and there to provide some tolerance to the flexing that occurs. The thing is, most of the time the flex track works just fine, even long stretches of flex track aren't an issue.

I'm wondering if the flex track is causing more problems than it fixes.  If you allow the track to move with any vibration from the train, sure, the track may not come apart, but that means that the track is also no longer dampening the vibrations from the train, which could be allowing the train to jump the track.  Non-sequitur: maybe you need to add some more weight above the front axle.  Try something like: http://www.bricklink.com/catalogItem.asp?P=73090b

well shoot, if you're gonna be all picky like that: https://www.youtube.com/watch?v=UVa4w5nQmoo :)

One thing I would say from my model train experience is that shunting (pushing) is more likely to derail a train than pulling, especially at speed.
There are a few factors that influence this in models more than we see in "real life":

The force is usually transferred via the couplings rather than buffers. This means there is more chance that the force will be applied at the wrong angle, forcing the leading elements off the track
The elements are too light. In real "multiple unit" trains where the driving force is at the rear of the train, the front elements are still very heavy, which mitigates the effects of force distribution somewhat - if you can add more weight to the Locomotive build then you may have more success.

A simple confirmation of this would be to remove the Locomotive from the train and see if you get the same derailments?

Yes, taking the locomotive off the track did help with that troublesome layout. But the same locomotive works fine at other times. I have a weighted 2x6x2 brick from an old fishing boat, I'll see if I can work it into the design.

Hmm, and it's not like a standard loco where you could flip the tender and loco around due to the massive cow-catcher...

I think your observation about the coupler applying force at the wrong angle is probably correct. I may have to bite the bullet and just rebuild the entire locomotive, but until now I never realized how tricky it was to make it work reliably. It would probably be easier to have my floor redone with hardwood instead of carpet.

Yes, that seems to be the considered opinion among other model train geeks - more so with the standard Hornby couplers where they are basically fairly thin loops pushing against each other ;)

I've taken apart, and rebuilt, my layout a few times and come to the following conclusion. It seems that the locomotive is extremely sensitive to any curve or gap in the tracks. The front wheels are attached via a technic pin, and essentially float under the front of the boiler, but the pin only really allows for lateral movement and not vertical. Thus, when the tender pushes the locomotive, if there is anything that causes the rear of the locomotive to  drop slightly or be twisted, the front wheels will lift and the train falls off the tracks.
The problem is worse, but not limited to, the flexible track. Sometimes a simple curve is sufficient, and the switch tracks are also problematic.
I tried putting a boat weight inside the boiler, This makes the locomotive heavier but doesn't really apply much force on the front wheels, and it means the center of gravity of the locomotive is not well placed for taking corners.
The other change I've made is to how the IR sensor is mounted in the locomotive. I rebuilt the roof of the cab so that the sensor pokes up out the top of the roof. I also re-routed the wires between the tender and the locomotive so that they are coming out the bottom of the tender, just above the coupler, and go under the sensor. I also pack them tightly into the locomotive so that there is no slack. This prevents the wires from pushing against the locomotive, which was causing at least a few derailments.
Finally, I removed as much flex track as possible, and put 2x4 plates on the track to hold the layout together.
The result is that the train runs acceptably well as long as nobody separates the tender from the locomotive.


text:
How can I tell which LEGO minifigure I found?
I found a mini-figure on the the ground by a recycling bin. I want to figure out what set/collection he belongs to but can't find anything other than how to tell what you're getting in a blind bag.
He's normal size for a mini-fig, not a shorty or anything.
He has a dark red pirate bandanna type hat with a "tail" hanging down his head.
His head is grey or grey-green with green eyebrow and cheek markings and pointy looking bottom teeth made to look protruding from his mouth.
His torso is a dark orange with a silver breastplate and brown straps on his back. Also there is a dark red belt. His arms are black and his hands are brown.
His pants are red but not dark red like his hat.
He's a mean looking guy and doesn't seem to match Pirates of the Caribbean or Lord of the Rings/Hobbit but looks like he would fit in with those sets.
Any help would be greatly appreciated.

A picture would significantly help identification.  Also, your minifigure may in fact not be one figure, but a composition of different figures.  We are talking about LEGO after all.

The torso is from Lando Calrissian.

The rest of the parts are from Kithaba.

They both came in the 2012 Desert Skiff Star Wars set

Thanks oddTodd, that looks exactly like him. Maybe someone was tossing old parts and he was just stuck together with what they had

That's an impressive bit of detective work!

@JustinCase to some people the point of Lego is that you can mix and match the pieces, and that's how they use it. Not everyone just buys it, assembles it according to the instructions, then displays it.


text:
EV3 RMIregulatedMotor Regulation Problems
I have problem with regulation of the motor when I control EV3 with Bluetooth.
Here is the code:
RemoteEV3 ev3 = new RemoteEV3("10.0.1.1");
    ev3.setDefault();
    RMIRegulatedMotor leftMotor = ev3.createRegulatedMotor("A", 'L');
    RMIRegulatedMotor rightMotor = ev3.createRegulatedMotor("B", 'L');
    EV3ColorSensor color_sensor = new EV3ColorSensor(SensorPort.S2);
    int color_id = color_sensor.getColorID();
    while(color_id!=7){
        leftMotor.setSpeed(300);
        rightMotor.setSpeed(300);
        leftMotor.setAcceleration(1000);
        rightMotor.setAcceleration(1000);
        leftMotor.backward();
        rightMotor.backward();
        Delay.msDelay(500);
        leftMotor.stop(true);
        rightMotor.stop(true);
        color_id = color_sensor.getColorID();
    }
    System.out.println("Establishing connection. Please wait ...");
    if(leftMotor!=null) leftMotor.close();
    if(rightMotor!=null) rightMotor.close();
    if(color_sensor!=null) color_sensor.close();

The problem is that the EV3's motor not continuously moving. It is stop a bit and then continue moving, it is kinda lagging or problems with regulation of RMIRegulatedMotor. However, if I change from RMIRegulatedMotor to RegulatedMotor and compile it directly with the brick not Bluetoothm, there is no problem at all.

Looking at your code, you're telling the motors to go at a speed of 300, then pause execution for 500ms, then you're telling the motors to stop, before continuing around again. Due to delays in communication you'll probably find that this will cause a stuttery motion that you might not notice when running it on the device.

Perhaps if you moved the calls to stop out of the while loop, then the motors would keep running until the colour id was 7.

I am so stupid with this function. Thank for your suggestion.

Pair programming for the win - often it just needs another pair of eyes ;)

Looking at your code, you're saying:

Set the motors to a speed of 300, acceleration of 1000
Run the motors backwards
Pause execution of your program for 500ms
Stop the motors
If you're not seeing colour id 7, go to 1.

Assuming that this was exactly the same code you had on the Brick, I'd guess the delays introduced by the communication will cause a stuttery motion that you might not notice when running it on the device.
If you pulled the following lines out of your while loop things would probably be smoother:
leftMotor.stop(true);
rightMotor.stop(true);


text:
Are coloured bricks used by Set Designers recycled to make black bricks?
I heard on a podcast of the Adam Savage Project that the master builders (designers of 'sets' of LEGO) are allowed to use as many blocks as they need to design a certain set. All of the bricks they use to design the sets are then thrown together, melted down, and made into black bricks as it is cheaper than resorting and less time consuming. Due to the pieces being used they are not allowed to be resold... Is this true?

Short answer: No.
Long answer: After searching around the web and finding nothing related to this subject, I fired an email towards LEGO Customer Service asking them this very question.
Today I have received this reply:

Dear Adam,
Thanks for getting in touch with us and sending us this question.
I have investigated the case further with our LEGO® product specialist team and I received the following answer from them:
No this is not true, the designers build the sets and then they have to get approved. If the set isn’t approved the bricks and sets stay out or on the designers desk, and the set is taken apart the bricks are used again.
  I hope this information will help to settle the debate.
We want to make sure we're doing a good job for you, so you’ll always find the link to a four-question survey in our emails. Please tell us how we did today:
LEGO Survey link
Please let us know if you need anything else.
Happy building!
Ildikó
  LEGO® Service


text:
Index of the City sets by category
I'm running trough bricklink, peeron and brickowl, but I can't find a "good" (I mean 'fitting my idea') index to browse across city sets.
Is there a kind of list like

vehicle

cars
trucks
planes

buildings

houses

7641

police station
...

does anyone of you have knows a such index ?
note: my english is not fluent, so, here are some precisions:
I'm looking for "houses" sets on ebay to complete my son's town streets.
He has a lot of vehicles, but a few buildings

No, but Brickset now provides the facility to enable one to be made. See http://brickset.com/article/12960/tags-a-new-way-to-search-the-database

While there is no explicit "house" tag, I would recommend browsing in Brickset's City theme: http://brickset.com/sets/theme-City
You can refine the search based on year (include only recent, therefore easy to buy sets), tags (building, shop, ...) and subtheme (airport, construction, police, ...).


text:
Looking for a Basic Lego set with mostly large bricks
I am looking to buy my son his first set of LEGO bricks (because my mom will not give me my old ones!!!). Most of the 650ish piece sets I have looked at contain a large amount of 1x2, 2x2, etc. I am looking for a set that has more 2x4s, 2x6s or bigger than those with more smaller pieces. Can anyone recommend a good set? It does not need to be that big of a set either, but if I could find one that would be great!! I cannot wait to finally own my own LEGO bricks that don't actually belong to my parents!!!

Most Lego kits have small parts. How old is your son? If he's old enough not to put the pieces in his mouth, just get a basic bricks set. He'll grow into the tiny pieces soon enough. He'll be 4 or 5 before you know it.

I don't think 2x6 bricks were ever common.

If you can get to a Lego shop, there is a Pick a Brick wall with mostly large bricks that you buy by the cupful for less per brick than you would pay in most sets.
These two sites:
http://www.brickbuildr.com/view/pab/
, and
http://wallofbricks.com/
show you the current(ish) contents of the Pick a Brick walls around the world, they are updated by fans so they might not be up to date.

There are always a range of bricks-only sets in production, the current one is called LEGO Basic Bricks Deluxe (Inventory). That is probably the closest you will get to what you want at this moment (November 2014).
With Christmas coming up, though, keep an eye out for a new brick set from a major retailer like Walmart. In the past there have been gems like LEGO 5512 XXL Brick Box.
Your best bet, however, is to go to Bricklink.com and find a store that sells ample quantities of used bricks in the colors and sizes you want.

isn't this exactly what the question was trying to avoid - most of the bricks in that set are 2x2 or smaller

I guess so. My point is that it's the closest to what he is looking for.


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Please help me identifying these spaceship parts - big sloping ring
Which lego set do these parts belong, I have a full box of random pieces, and I wish to build something starting from this. Thanks

It's from a LEGO UFO set from the late 1990s. You can see all the sets in this theme here: http://www.bricklink.com/catalogList.asp?catType=S&catString=34.311. What you have is most likely the #6975 Alien Avenger:  http://www.bricklink.com/catalogItem.asp?S=6975-1


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Help identifying a black round piece with three rings
I'm on a personal project to document the brick list for building every one of Chris Deck's Star Wars miniatures (http://sw.deckdesigns.de/minis.htm), and I'm unable to find in the Lego catalogue or Bricklink a canister-like black piece with three different radius values. Look for the second step (3rd picture) in http://www.brickshelf.com/cgi-bin/gallery.cgi?f=93630.
Thanks!

I believe that the part you are looking for is 6221 (Peeron 424) :

This part was most commonly found in Technic sets and was often used as a spacer on longer pins or as a crank handle:

Here it is on Bricklink.

That is exactly what I need.  Thanks, @jncraton!

For the record, this part is also one of the two glued halves forming the old pin joiner (http://brickset.com/parts/design-75535). Its LEGO reference is 6221 (http://brickset.com/parts/design-6221)

@Ender If this answer helped you, you should mark it as accepted to let others know that it's solved, and to give jncraton a bit of an extra thank you.

I know!  My excuse is that I couldn't mark it as the answer as I didn't have enough score (or maybe I clicked on the "Vote up"?...now I'm not sure anymore).  I was waiting to get some more points to do it, and I did it.  Thanks for helping me remember anyway!


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Lego EV3 - Get output device type, opOUTPUT_GET_TYPE
I would like to know what kind of motor (XL, L) is connected to EV3 output port (A|B|C|D). I need to use direct command:
Instruction        opOutput_Get_Type (LAYER, NO, *TYPE)
Opcode             0xA0
Arguments          (Data8) LAYER – Specify chain layer number [0 - 3]
                   (Data8) NO – Port number [0 - 3]
                   (Data8) *TYPE

so request should looks like:
unsigned const char opOutput_Get_Type[] {
    0x09, 0x00, // bytes in message
    0x00, 0x00, // message counter
    0x00,       // DIRECT_COMMAND_REPLY
    0x01, 0x00, // 1 value will be returned
    0xA0,       // opOutput_Get_Type
    LC0(0),     // LAYER 0, first brick in chain
    LC0(0),     // port A
    GV0(0)      // returned value
};

When I send it to brick a get response:
04000000 0400
          ^-
          DIRECT_REPLY_ERROR

which stands that error occurred. Motor is connected to port A. What am I doing wrong?

Checking the source code, it appears that the opOutput_Get_Type command is not implemented. In both links, it is mentioned in the comments, but there is nothing in the actual code.
Unfortunately, I am not finding a different way to get this information.

Thanks for the tip. I've found command opOUTPUT_GET_TYPE = 0xA0 in bytecodes.h and parameters which it takes http://topikachu.github.io/python-ev3/OutputLibrary.html.

The one who wants to know device type should use direct command:
Instruction        opInput_Device (CMD, ...)
Opcode             0x99
CMD                GET_TYPEMODE = 0x05
Arguments
                   (Data8) LAYER – Specify chain layer number [0 - 3]
                   (Data8) NO – Port number [0 - 3]
Returns
                   (Data8) TYPE
                   (Data8) MODE - Device mode [0-7]

In order to discover all ports we should send
unsigned const char opOutput_Get_Type[] {
    0x35, 0x00,                                 //Message size = 53 bytes (0x35 hex)
    0x00, 0x00,                                 //Message Counter
    0x00,                                       //DIRECT_COMMAND_REPLY
    0x10, 0x00,                                 //16 values will be returned... 8 pairs (type, mode)
    0x99, 0x05, 0x00, 0x00, GV0(0), GV0(1),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_A, TYPE, MODE
    0x99, 0x05, 0x00, 0x01, GV0(2), GV0(3),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_B, TYPE, MODE
    0x99, 0x05, 0x00, 0x02, GV0(4), GV0(5),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_C, TYPE, MODE
    0x99, 0x05, 0x00, 0x03, GV0(6), GV0(7),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_D, TYPE, MODE
    0x99, 0x05, 0x00, 0x10, GV0(8), GV0(9),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_1, TYPE, MODE
    0x99, 0x05, 0x00, 0x11, GV0(10), GV0(11),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_2, TYPE, MODE
    0x99, 0x05, 0x00, 0x12, GV0(12), GV0(13),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_3, TYPE, MODE
    0x99, 0x05, 0x00, 0x13, GV0(14), GV0(15),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_4, TYPE, MODE
};

In return we'll get response i.e.:
13 00 00 00 02 7e 00 7e 00 7e 00 7e 00 08 00 07 00 07 00 7e 00

which stands (based on http://ev3.fantastic.computer/doxygen/types.html)
13 00   //message size = 19 bytes
00 00   //message counter
02      //success
7e 00   //nothing on port A
7e 00   //nothing on port B
7e 00   //nothing on port C
7e 00   //nothing on port D
08 00   //M-MOTOR-DEG on port 1
07 00   //L-MOTOR-DEG on port 2
07 01   //L-MOTOR-ROT on port 3
7e 00   //nothing on port 4


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Trying to get a modified traffic signal challenge worked out
The challenge is for a robot to go around the perimeter of a rectangular field and execute 90 degree turns when it gets within 4.5 inches of a wall.  Simultaneously, if the bot encounters a red flag, it needs to stop until the flag color turns green.  At that point, the arm holding the color sensor needs to dip to avoid the traffic signal, and once it is passed, continue on it's way.

I have tried running two threads, one where the bot encounters a flag (which I have constructed a switch for cases red and green), while the other is where it encounters a wall.  I think these two threads need to be encased within an infinite loop, but I can't seem to make it so.

You can use finite state machine. In this case you will have these 5 states:

RUN

Action: turn on the motors for moving straight
Transition to state TURN in case of event: ultrasonic sensor detects obstacle closer than 4.5 inch).
Transition to state WAIT in case of event: color sensor detects red color

WAIT

Action: stop motors
Transition to state CONTINUE in case of event: color sensor detects green

CONTINUE

Action: move forward a bit while avoiding the flag
Transition to state RUN immediately.

TURN

Action: Turn the robot 90 degrees right, increment the rotations
Transition to state STOP in case of event: rotations = 4
Transition to state RUN in case of event: rotations < 4

STOP

Action: Interrupt the program.
Here is the code I've just scratched without a testing, let me know if it works:

You can enhance the state machine to check for the flag during rotations, too. :)
You can learn this robotics topic from the great book by Daniele Benedetelli - LEGO MINDSTORMS EV3 Laboratory.


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How to program light sensor to follow moving light using NXT
Cannot figure out how to simply program Lego Mindstorm NXT robot to follow another moving robot that has a bright LED light attached to it.
Currently my programme looks like this:

It sounds like you are unfamiliar with how the light sensor works.  First off, it's not directional.  Secondly, it detects all light, including ambient light, so your LED may not be bright enough to even register on the light sensor.

A few things:  The light sensor has to be pretty close to something in order to be very functional.  How close will the other robot be?  How much ambient light would there be in the room?  Do you have more than one light sensor?  Also, you would probably get much more reliable/feasible results using an ultrasonic sensor.  Is there a reason why you must use light?

If I were you, I'd make it this way:
The leader robot has a very bright light shining backwards, but not in a tight beam, rather a wide cone, so it can be seen from the back easily.
The follower robot has the light sensor facing forward, with a cowl around and in front of the sensor in order to narrow its sensing angle. In other words, the sensor is modified in such a way that it only picks up anything if the light source is directly in front of it, not to the sides. This will help filtering out background "noises" (ambient light and other light sources).
Then the follower robot runs this pseudocode:
while true // enter stopping condition here if required
  while light is visible // current light value is over a threshold - experiment with this value
    go forward some amount
  // if light is not visible the while loop exits and we need to find the light
  store current light level to variable FRONT
  rotate 10 degrees to the right // experiment with various values, maybe less is enough, maybe more is needed
  store current light level to variable RIGHT
  if RIGHT < FRONT // the light probably moved to the left
    rotate 20 degrees to the left // twice the amount in the previous turn
  // else the light probably moved to the right, where we are currently headed
  // so there is no need to rotate further, just continue with the next iteration,
  // checking if we see the light now

This way the follower will go after the leader while it is headed in the right way, but when the follower loses the leader, it stops and turns around to look for the light.
This method however has a drawback. If the follower is slower than the leader, it will be left behind during the "stop and look around" phases, but if the follower is faster, it will run into the leader from the back.
You could remedy this by giving the leader a bumper on the back connected to a push button (pressure sensor), and program the leader to only move forward when something (probably the follower) has pushed into its back bumper.
Let me know if you need additional help.


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Trouble with Commander app: Using buttons to control motors
I'm having trouble with the Commander app for Android. I've put an EV3 into set 8448. I'm using one of the large motors for propulsion and a medium motor for rack and pinion steering. I don't have the remote (using the education set) so I'm trying to use my phone as a remote instead. I downloaded the Commander app.
I went into "create my own". I can use a slider to make the car go backwards and forwards, however, I tried to set up two buttons for steering, one button to make the medium motor go one way and another button to make it go the other way. Only one of the buttons works. It's only possible to make the medium motor go one way, not the other. How can I make it so the button controls can control the motor in either direction?
Any help would be greatly appreciated.

You cannot have more than one control per motor. If you have two controls, the signals are essentially sent to the EV3 at the same time, so only the second one will seem to work because it immediately changes whatever what sent by the first.
In your example, with 2 buttons, the buttons either command the motor to move or stop. If neither button is pressed, both are telling the motor to stop, so no problem. But if you press the first button, it tells the motor to turn, but the second button is telling the motor to stop. Since the EV3 got the message from the second button last, the motor stops and it appears that the first button does not work.
So, if you want to use the Commander app for this, you will need to use a different control that can turn the motor in either direction with just one control such as a slider or tilt.


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Direct control of EV3
I need to control a car with an EV3 brick. I want to control it remotely. The trouble is, I'm using an education set so I don't have the remote. What means of controlling it remotely could I use? I already tried it with some Android phone apps but none of them worked quite right. It's a car that uses rack and pinion steering and the apps seemed to be better suited for skid steering. Is there some other way I could have remote control of it? Perhaps through a laptop or a Playstation controller or something else?
Any suggestions would be greatly appreciated.

In relation to both these questions, I'm guessing the main issue is the Rack and pinion nature of the steering - you really need to use a servo motor for the steering, where it only travels between a limited number of degrees, and can return to "home" when you release the control.

Do you really need an EV3? The RC car chassis is a fairly common LEGO construction, complete with an infrared remote. If you need it to be programmable, you can still stick an EV3 with its motors and sensors on top of the standalone car chassis.

There is always the .NET API for Windows 8/ if you don't mind programming an app yourself (this would work for Windows/Windows Phone 8). The sample provided would allow you to control the individual ports of the brick but it doesn't take much to change this to control multiple ports from one button press.
https://github.com/BrianPeek/legoev3
Sadly this solution is probably no good if programming isn't your strong suite :/

The legoev3 project moved to https://github.com/BrianPeek/legoev3

Here are some ideas...
Hardware options:

Purchase the EV3 Infrared Sensor and Beacon (This is a nice option since it can do more than just remote control)
Purchase the Hitechnic IRReceiver Sensor
Purcahse a mindsensors.com PlayStation controller adapter

Software options:

Use the Monobrick Remote.
Read the articles about remote control from Sioux.NET
Use the Lejos remote control library
Use Microsoft Robotics Studio (can connect a gamepad plugged into the computer to the EV3)

Here is a short curses [1] script written in Perl with which you can use the arrow keys on your usb/bluetooth/WLAN connected PC to control the EV3.
It uses ev3duder, part of c4ev3, to establish a connection to the device and then keep sending direct messages to the motors. That way you don't need to modify any software on the EV3.

[1]: Curses is a terminal control library for Unix and is only used to capture the arrows keys. Check Stackoverflow for other means to do so on your Platform.

You can use second EV3 block (of corse if you have one)
If you know a little bit of Mindstorms then you need to use a sending block (it's blue).
But here is the algorithm you need to make two programs the Master program and the Slave program. (One little secret: it will better work if will load the programs with the USB cable turn off Bluetuth on your computer).
Here is the skeleton of the Master program
And here is the skeleton of the Slave program
Here I am making a program  where by a big A motor I am controlling the speed of my robot but you can add anything like gyroscope or touch sensor.

This sounds like a possible option. Would you be able to edit your answer to flesh out how this would be accomplished?

It is possible to connect a Playstation controller (Sixaxis or DS3) directly to the EV3 brick over Bluetooth. Here is how I do it:
http://www.pabr.org/bricks/brickhid/brickhid.en.html
There is a servo emulation mode which should support rack-and-pinion steering.
Note that this is a quick-and-dirty proof of concept with several limitations:

A PC is needed to upload and start a native program on the EV3 brick at every power-up.
A WiFi dongle must remain attached to the EV3 brick.
Joystick events are mapped to motor commands directly; they cannot be processed by EV3 programs (but you can customize and cross-compile the C source code).

The proper way to do this is with a custom firmware with full Bluetooth HID support.

I would definitely use bluetooth instead of wifi, i've tried the dongle but it doesn't operate very smoothly. If you are having trouble with the steering I would use different controls on the app. Also make sure to use the official app as I have not tinkered with other apps yet.

I have long sought such a program, eventually wrote it himself. The basis is - on the basis of EV3Messenger its added buttons and handling keyboard events. I can send the latest version

Welcome to Bricks.SE. Can you elaborate on your program - perhaps add a few representative lines that explain the concept, so that others can write their own version (of course providing a link to your own code is always allowed). That way, even if you cease to respond to people's requests for your code, the answer still has value.


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Which is faster: M motor or XL motor?
I understand that the M motor has an adequate amount of speed, and the XL motor is best known for its torque. But is the XL motor really faster than the M motor? Or is it the other way around? I am asking this question because I recently saw the L motor, and one reviewer said "It has the speed of the M motor but the torque of an XL motor." I am assuming this means that the M motor is faster...?

XL (8882):
It delivers a maximum torque of 90,4 mNm (600 mA). Without load its rotation speed is around 220 rotations per minute.
L (88003):
It delivers a maximum torque of 45,4 mNm (450 mA). Without load its rotation speed is around 380 rotations per minute.
M (8883):
It delivers a maximum torque of 40 mNm (300 mA). Without load its rotation speed is around 380 rotations per minute.

Well, I take it you are telling me that the M motor is faster. Now that I think about it, the M motor isn't the fastest motor that LEGO has made. The 9v 2838 motor is by far, much, much faster. http://www.philohome.com/motors/motorcomp.htm

@TaylorGarrett L and M motors have the same unloaded rotation speed (380rpm) which is faster than the XL (220rpm), however they both have lower torque, which means that they will stall under lower loads than the XL.

Theoretically, in terms of power (speed • torque), the XL Motor is faster than the L Motor and M Motor. The reason being, you can gear up the XL Motor 2:1 and have the following output: running torque of ~7 N.cm & rotational speed of ~290 RPM. However, a small amount of these measures will be lost due to friction and decreased efficiency (by transferring drive through gears). Regardless, comparing these measures to the normal output of the M Motor — running torque of ~3.63 N.cm & rotational speed of ~275 RPM; and the L Motor: running torque of ~6.4 N.cm & rotational speed of ~272 RPM — and we have a clear winner, as far as running torque performance goes. Also, it is worth mentioning that the XL Motor has significantly higher efficiency than both the L Motor or the M Motor.
RPM measurements listed here are the loaded characteristics, not no-load. This is why the RPM numbers listed here are lower than what others have said.
Torque and speed measurements are according to http://www.philohome.com/motors/motorcomp.htm

It really depends on what you're going to be using it for. I'm in the middle of motorizing the fancy branded Lego Porsche and I was gonna use a couple of L Motors to drive the wheels and a servo to handle the steering, but after some research I found that because of all the gears going through the gear selection and drive-train, a powerful amount of torque is required and as Damon very correctly stated, the XL Motors are much more efficient in terms of performance. You might not be getting the same speed but you'll end up regretting buying the L motors due to their lack in torque. To solve this issue with my Porsche I just used a BuWizz controller instead of the old IR setup for more speed, flexibility and less weight as I don't need a receiver.

I bought an XL-Motor a couple of weeks ago, but when I saw a video of the M-Motor I knew it was faster. It seems to be that the XL-Motor can pull so much more due to the increase in the size of the whole motor but takes a lot more time to do a full 360-degree spin, and for the M-Motor it takes about less than a second to do a whole spin. If you want to buy a motor due to its speed but lack in torque, buy an M-Motor. If you want to have a stronger motor that won't get jammed easily, buy an XL-Motor.
If you already have an XL-Motor (or L-Motor) and you don't want to buy another (M or L) motor just increase the gear ratio. Take a huge gear wheel and get a small gear wheel and connect them to your build. Basically what is happening here is the big gear wheel is taking longer to make a whole 360 degrees spin and while it's trying to do that the small gear is going twice as fast as the big gear and therefore makes it go fast.
Here is an image of the motor:

To be honest, both small and big gears will take same amount of time to make 360 degree turn on the same motor. The difference in changing speed/torque these make make is due to diameter (and subsequently number of teeth) each gear has.

Then how come the gear goes faster then the motor even though it has less teeth and how can the radius of the whole 360 degree spin go the same speed as the smaller gear?  I mean the gear is big so it takes longer but if the gear is decreased to the size of the other gear they go the same speed and theres no diffrence in speed.

I think you are confusing "gear" with "combination of gears". One single gear attached to the motor axis will turn independently of its size. Usually, adding an image to the answer will be very useful for illustrating what you try to explain. Welcome to Bricks.SE.

As I mentioned, both small and big gear turn with the same angular speed or revolutions per minute as the motor does. Angular speed isn't a parameter of the gear, but rather of the motor itself. You can test this by placing both sized gears on the same axle attached to a motor - they will spin with same speed. Placing each gear independently will result in same angular speed. What you are referring to here is related to gear diameter/radius/circumference or number of teeth of the gear. The bigger the driver gear the quicker driven gear will spin and vise versa.

Let me clear this up, seems like you're confused about how gears mysteriously move faster/slower when connected together. if you put one single small gear on some random motor, it will rotate. A bigger gear on the same motor will seemingly move slower. Why, you ask? Because the size of the gear is bigger, therefore making the rotation longer, as @Alex said. (same goes for wheels or any other round object) You can also connect gears together so that their teeth touch in order to customize speed, too.

(continued) You can have a bigger gear attached to a motor and a smaller gear right after it, resulting in the smaller gear rotating considerably faster than without that bigger gear. If the smaller gear is the one that gets motorized then the bigger gear will end up slower than usual. The combination of gears is called a "gear train". The gear that is being moved/motorized in the gear train is called the input gear. And the gear at the end of the gear train that gets moved by the other gears is called the output gear.

Oh, and putting two gears together that are the same size and have the same number of teeth will result in identical speed, no matter which one is motorized.

I know that i just want to make it go faster

Do you have any ideas?

@Nerd I will send another example of your request when I get the chance (likely that I will do it tomorrow), I'm very busy right now. Sorry to put you under this trouble for so long.

@Nerd Nevermind, I already did it right now. Also, you can click the checkmark next to my answer on your question to mark it as accepted/correct.


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How can I wire up the LEGO 2838?
I would like to know how to hook up the LEGO 2838 9v motor. I understand that the Power Functions extension wire is compatible with the 9v system, but how on earth do I wire them up?

To wire 2838 motor, you have to use one PF extension cable, one end connected to PF power source (either battery box or IR receiver), the other end has a 9V compatible plug on bottom. Unfortunately, 2838 also has its connector on bottom, so you also need a 9V cable (such as this one) to connect them.

You could also use an extension plate (2x4 or 2x8) underneath the motor, so that you can plug the PF extension cable on it.


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Programming sensor to follow light

Cannot get sensor to follow light on other moving robot.

This is a duplicate of your previous question.  You shouldn't open multiple questions to solve the same problems.  Update your existing question and respond to some of the questions in the comments and you will get a better answer.

I've moved your image into your original question for you.


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Can additional MyBlock icons be added to the EV3 palette of icons available in the MyBlock builder?
I'm a big believer in using MyBlocks when using EV3.  For FLL teams, every robot needs to move forward, backward, turn right, turn left, arm up, arm down.  Even before a robot is built, those MyBlocks can be created.  However, none of the icons on the available palette of icons seem suited to the task.
Is there a way to add icons to the palette?
The palette of icons for the parameters is much more useful, so for now, we'll ignore that palette.

Go to the directory

(for home edition) c:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS EV3 Home Edition\Resources\MyBlocks\images\
(for edu version) c:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS Edu EV3\Resources\MyBlocks\images\

And create a group of 3 icons for each new icon:

PolyGroup_NNN_NAME_Diagram.png [size 34x34] - visible in the diagram
PolyGroup_NNN_NAME_Palette.png [size 25x25] - visible in the command palette
PolyGroup_NNN_NAME_Palette_MouseOver.png [size 25x25] - visible in the command palette while moving the mouse over the icon

Where

NNN is a next available number (98 icons already installed), so continue with 098
NAME - use some name

Restart the SW and open MyBlock builder, you will find the added icon.
It will not work, if you open your code on another EV3 installation without your modifications.


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After adding a MyBlock icon to the EV3 palette of MyBlock icons, how can the new icon be associated to an existing MyBlock?
After following the advice given in adding a MyBlock icon to the EV3 palette, can the icon be associated to an existing MyBlock?
Something better than copy/paste the contents of the existing MyBlock into a new MyBlock.

follow this: http://bricks.stackexchange.com/questions/4622/is-it-possible-to-edit-a-my-block-input-parameter-value/4689#4689

As mentioned in this answer, since v1.3.0, it is possible to edit my blocks.


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LEGO Technic part Numbers
My daughter got the LEGO Technic - Service Truck set. When we looked at the instructions, we saw a different notation on parts.
eg: the beams (cross beam) it has number 5 in white circle. what does that 5 stand for. Other instructions in same book have the number 3 or 7 in white circle.
Can anybody advise what these numbers mean?

Beams, axles, panels, and axles connectors usually have numbers next to them, to uniquely identifies the piece:

for beams and axles, the number is the length (length in number of holes)
for panels, it identifies the panel (and the panel mold contains the same number)
for axle connectors, it identifies the angle (again, the same number is part of the mold, and visible on the piece)

Same pieces with different colors have the same number attached

These numbers indicate the length of the beam or axle shown.
For a beam, this number is the number of holes it has. For an axle you have to hold it next to a beam and than count the number of holes.

Also, the instructions usually have a 'ruler' on that page of instructions so you can measure it even without a beam or brick of that length.


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Part identification
Can you help me identify which part numbers these parts are? I can't find them on Lego's site or on brickset.com:

Edit:
I've found the two dark grey bricks in the left photo, so that just leaves the yellow one, and the other two photos.
Thanks!
Ben

I'd say the yellow part is listed on BrickSet as "Lamp Holder" or "Plate, Modified 1 x 1 with Clip Light - Thick Ring", 4081 on BrickLink, Peeron, etc.
The light grey piece is from the Flick Missiles, and is listed on Brickset as "3 M.Arch W.Knob And Shaft Ø¸3.2" or "Technic, Pin 1/2 with 2L Bar Extension (Flick Missile)", 61184.
The final piece is "Mini Fig. Back Palte W. Knob" or "Minifig, Neck Bracket with Back Stud", 42446
For completeness, the other two are:
"Angular Plate 1.5 Bot. 1X2 1/2" on Brickset or "Bracket 1 x 2 - 1 x 2 Inverted", 99780
The tile I couldn't find on Brickset other than in Rebrickable inventories where it's listed as "Tile 1 x 2 with Joystick and Vehicle Control Panel Pattern" (3069bpr0090) or on BrickLink as "Tile 1 x 2 with Vehicle Control Panel Pattern", 3069bpc1


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Dimensions for EV3pieces
I need to know the dimensions of the EV3 pieces for a school project (in mm). Does anyone know?

Do you mean the LEGO technic bricks or the EV3 control brick and sensors? Please be a bit more specific.

I could only find the size of the servo motors:
Large servo motor: 14x7x5 modules -> 112x56x40 mm
Medium servo motor: 3x4x9 modules -> 24x32x72 mm

I don't know of any comprehensive parts dimension reference, but following should help you get started.
You can calculate part dimensions using fundamental dimensions of LEGO parts. The distance between holes in technic bricks is 8 mm (8 mm is one of core dimensions in whole LEGO).
So for example, lets take a beam (aka liftarm) with 7 holes, then length is 8mm*7=56 mm, and width is 8 mm.
Same rule for pegs, e.g. black pin with friction (used to connect 2 beams) has length of 8mm*2 = 16mm, diameter of 4.8mm - 6.2mm (depending on what part of pin you would measure).
LEGO technic axels follow same rule: their length is a multiple of 8.
You can read more on LEGO dimensions at  http://www.robertcailliau.eu/Lego/Dimensions/zMeasurements-en.xhtml


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Why is there no set with much RC Straight tracks?
after visiting many Lego events (brickmania, antwerpen, BE), I wish to expand my train layout much more than adding a box or two of 7499 ...
Why does Lego didn't released a set with, for example 24 straight track ( #53401 )
Even if 7499 contains flex rails, I don't like these, they are noisy.
Any tips for finding some ??
I can't imagine peoples who exposes layout in 5 meters by 8 meters with 4 tracks have bought a pallet of 7499 !

According to Brickset there are 8-8 straight track pieces in all of these sets (including the sets with straight tracks without metal conductors):

7896
7499
3677
7898
7939
60052
60205
60337

The 60098: Heavy-Haul Train has 12, and both of 60336: Freight Train, 60198: Cargo Train have 16 straight pieces.
This seems to be the maximum amount, even the large complete train sets do not contain more than 16 straight tracks.
You might have more luck purchasing them piece by piece from other AFOLs, or see if there is a Pick-a-brick shop in your area.


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Is there a LEGO clamping tool?
Sometimes we cannot easily attach 2 LEGO pieces.
Is there a tool to help clamp together LEGO pieces that are very tight?

I agree that sometimes adding smaller plates can be tricky - the issue is usually caused by misalignment of the studs and holes.
You could use one of the Brick Separators in reverse (i.e. add the brick to the separator and then attach it to the other part), or you could try adding a larger brick first temporarily to help you line up the piece.
The other elements that we have trouble with are the hinges and clips, and for that I've found just taking your time and easing it gently is the best option.

Agreed. Most of the time alignment is the issue, and clamping pieces will just break them.

If you’re using regular bricks and plates, there is really no sure way to tightly lock them together. The only way to ensure secure assembly is to use special or Technic pieces.
If you use special bricks with “knobs” separating each row or layer with two rows or layers of plates, you can then use plates across the knobs.
A more secure assembly would be to use Technic bricks with connector pegs, separate each row with two rows of plates and use Technic beams across the connector pegs.
If you have a wall structure that is two units thick you can also use bearing elements which are 2×2 bricks with snaps.


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LEGO STUDIOS Moviemaker Set
I was offered a set from LEGO STUDIOS line, very well maintained but without his software.
Can someone share the installation CD in English of LEGO STUDIOS 1349 Steven Spielberg Moviemaker Set or where can I download the software in English??

Generally speaking, you should ask LEGO to send you a replacement disc. In 2006 they sent the software without any further cost according to this forum thread.
Note though, the official software is almost 15 years old by now, and so it is likely incompatible with any modern computer. There is a version that is compatible with XP, but anyways it is generally accepted that the official software is far worse than the best generic alternative.
Keeping this in mind, I would rather recommend you to look around for other generic video-editing software: Free software collection of a hobbyist LEGO movie group

I do have a copy of that floating around somewhere*, and can attest to the fact that it only worked directly with Windows 98.
LEGO did release an updated CD for the "Mindstorms Vision Commander" set that worked with Windows XP that should enable the drivers for the webcam which I also have somewhere*, but I was unable to install the correct drivers for the Camera (effectively a low-spec Logitec webcam iirc) from the install media on a 64 bit Windows 7 machine (I also tried both compatibility settings and Windows XP Mode) - this seems to be a limitation of the Camera.
The software itself was quite good for editing (based on a Pinnacle Software video editor), but the rendered output was far worse than the original/in-app player.
If you have an Apple device, you will get better results from the LEGO Movie Maker app, which provides decent live onion skinning in the viewport, as well as a better camera and output. Other devices have other apps available as well.
* In this case "in a box in the loft" I think - not sure how accessible it is, but I need to get some stuff down this weekend, so will see if I can dig it out.

I managed to find the English version for Windows XP:
http://www.mediafire.com/download/h88sxgzkfs2278x/studio.iso