What's the difference between F4 or F7 flight controllers? What is the difference between the STM32F411 and the STM32F722RET6 processors in flight controllers? What are the advantages of having the F7 processor over the F4 processor?

There are a few differences:

Firstly, the F7 chip used in F7 flight controllers operates at a much higher frequency, so can handle more operations per second.

This is useful when you want to start adding lots of dynamic filters, for example RPM filtering, alongside features such as antigravity.

Whilst an F4 can handle almost anything you will want to throw at it in this respect, it will not be able to do so forever (the F3 used to be standard but is now lacking features). Therefore, F7 is better for future proofing.

F7 flight controllers also have extra UARTs. This can be very useful if you want lots of extra features, for example SmartPort telemetry, Smart Audio, GPS and camera control. However, it is not the end of the world if you don’t have as many UARTs as you want as you can use softserial to add software UARTs to your FC. Of course, this also takes up processing power so an F7 may cope better.

Finally, F7 flight controllers have built in inverters on their UART ports, while F4's do not. So an F7 FC can handle any inverted signal "as is" on any of its numerous UARTs, while F4 flight controllers have a dedicated external inverter chip on the PCB connected to one of the UARTs.

Because of that, F7's make it easier to use UARTs for SBUS or other inverted signals as it means you can hook them up anywhere without any inversion mods, while on an F4 controller you can only use the special inverted pads (of which there is usually only one, labeled "SBUS").


Calculating the range of an FPV drone It's been a long time since I studied Electronics and Communications Engineering, but if I recall correctly, it should be possible to calculate an estimate for the range of an FPV drone given the transmitter power, the antenna gains of the transmitter and the receiver, the frequency of operation, and the receiver sensitivity.  [I don't have the equation to hand, and my memory isn't what it was, but I'll add it when I find it]

Now, clearly there will be other external factors that might adversely affect the FPV range, so the calculation would only give a 'maximum' range under ideal conditions.  However, with that caveat, it seems to me that it would make sense to use this calculation as part of the design process to help determine the components that will be needed when building an FPV drone.

However, none of the tutorials that I have seen make that calculation, and the expected range is rarely even mentioned when they discuss selecting the components for a drone.  A fairly typical example would be  How to Build an FPV Drone.

So my question is:

Is it worth calculating the expected range for an FPV drone as part of the design process, and as a guide to help to select components for the drone?

I'm going to give you the answer first:
Yes, it is worth calculating the approximate range if you're building a (very) long-range aircraft. However, theoretical calculations will usually be such a crude approximation of reality that you can't rely on them, and the actual maximum range will depend on a myriad of factors besides what you can consider in the approximation.

If you're flying short-range, near obstacles (or inside of them!), doing acrobatic maneuvers, etc, the local conditions, attitude of your drone, its proximity to things, etc at each particular moment will affect the performance of your video link orders of magnitude more than any theoretical range. Things such as where your antennae are pointed and how directional they are, what kind of noise reduction your receiver has, and where you are standing suddenly become extremely important and intimately connected to the configuration of the building or other environment that you're flying. Sometimes, just moving your receiver several centimeters to the side could make a huge difference in the clarity of the received signal, or lowering your transmitter's power can make the link perform better due to less multipath interference.

So what people usually do is they have some known values of range and general performance for certain combinations of gear, and they consider how much a certain change to that gear will affect this performance. As in, swapping a 3dB antenna for an 11dB option might give you an 8dB stronger signal, which corresponds to 4dB (~2.5x) more range in open air versus the alternative under the same conditions; or it might give you the ability to punch through that wall (while your less-directional omni antenna covers the rest of your surroundings). Maybe upping the VTX power twofold could give you sqrt(2)=1.41x more range even through that wall. Or it might give you more interference instead. So after making that hypothesis, you implement the change, go and test it and see if it really works this way; It might or it might not!

Okay, now comes the nerdy part.

I don't know the exact formula you're speaking about, but I'm going to reason my way through this just for kicks.

So, our goal is to have a signal at the receiver that's higher than its sensitivity (which represents the weakest signal that the receiver can detect and demodulate). Our signal path is as follows:

Original signal -> transmitter's amplifier gain -> (feedline loss) -> TX antenna gain -> path loss from travel between antennas -> RX antenna gain -> (preamp?) -> receiver.

(scroll it).

The signal is multiplied at every step except where it is reduced while traveling through the air, so we need the product of all gains multiplied by the loss factor to be higher than the sensitivity.

So our max-range equation is:

AmpGain*Gain1*Gain2*PathLoss = RxSens.

In the simplest, ideal case, where we assume that there's nothing around except the two antennas (free space), the losses from transmission are inverse-square:
FSPL = wavelength/(4Pi * distance²), from which we get:

AllGains*wavelength/(4Pi * Distance²) = RxSens;
4Pi * Distance² = AllGains*wavelength/RxSens;
MaxDistance = sqrt(AllGains*wavelength/(4Pi*RxSens)).

And here comes the caveat.

We don't live in an ideal world.

We're not transmitting in free space. There might be buildings or trees or rain or anything else in the way, too. Worse, it doesn't even have to block your line of sight, as objects near the line will cause diffraction of your signal which can interfere with your reception if they are within the fresnel zone. The ground itself will often be the biggest source of such interference at larger distances, sometimes reducing the propagation factor to an effective inverse-fourth-power law.

Also, consider that the max-gain vectors of your antennas are not always pointed at each other; while you can use an antenna-pointing device on the ground, your aircraft will pitch and roll, reducing the transmitting antenna's gain in your direction.

The earth's atmosphere can affect your signal significantly as well, and it will do so differently each day, both in terms of how much and in terms of how.

For all of those factors, while you can predict roughly how they are going to affect your range, there's a lot of things about them in each particular location and at each particular time that you simply don't know. And since signal-modifying factors stack by multiplying, the discrepancy can get pretty big pretty fast.

Your receiver isn't ideal, either. It will probably start to corrupt the signal in various ways as you approach its sensitivity level. You're unlikely to ever see this, however, because long before it reaches that critical stat of your receiver, your precious signal will drown in...

Noise.

Noise is the worst enemy of anyone working with high-gain systems. It's the third law of thermodynamics personified. Thousands of manmade and natural radiation sources around the planet bombard everything around with random radio waves. Even if you exclude those, outer space is actually quite noisy as well. Your receiver itself generates noise internally; in fact, for most gear including your receiver sensitivity itself is defined by that internal noise level. Still, external noise tends to be orders of magnitude more powerful, and whatever the source, you don't want any of it.

The total strength of noise as received by your gear is called the noise floor, and that floor is lava. No matter how sensitive the receiver, the moment your signal level dips below the noise floor, it's gone: still out there, but you can't tell it apart from the noise to decode it properly anymore.

Depending on the nature of your signal, it can even become totally unintelligible before it reaches the noise floor, at several dB above it. Usually, the higher a signal's bandwidth (which is closely linked to data transmission rate), the sooner it's overcome by noise. Some advanced digital transmission modes can extract a message from well under the noise floor, but in order to do that they transmit several bytes per minute.

Video is a notoriously high-bandwidth type of data, both in the internet and in radio. Analog video especially so, as it has zero compression. So it gets disrupted by noise rather easily. On the other hand, zero compression implies lots of redundancy in the data, and redundancy allows for error correction. Do you know what's one of the best signal processing and error correction machines in the world? The human brain! Even when a video signal is almost entirely eaten up by static, we can still see shapes in it. So for video, the intelligibility threshold seems to be just at the noise floor mark, give or take a couple dB.

You can fight noise in various ways. Usually, if most of it is coming from certain sources on the ground, just using a directional antenna helps by attenuating signals from unwanted directions. Sometimes, if the noise is just the regular background entropy kind, it doesn't. A good frequency selectivity of your receiver (i.e. its ability to ignore signals that aren´t the target frequency) also helps tremendously.

An interesting way of fighting noise is signal-stacking, as done by receivers like RapidFire or True-D X: Instead of simply switching to the antenna with the highest signal, they use signals from both and merge them into one. Since the useful signal is the same and noise is random, the signal adds up while the noise mostly cancels out. Astrophotographers use the same technique to get stunning clear pictures of the sky, except that they have to stack hundreds of extremely noisy photos. The digital communication modes I mentioned earlier also work this way by sending multiple copies of the same transmission.

Video is still a high-bandwidth signal, however, and you've only got two copies of it to stack, so the gains from the likes of Rapidfire are far from dramatic, but it'll win you a couple of additional dB over the noise floor. Beware, though: such receivers depend on a special sync signal in the video to do the adding correctly, and when the noise eats that... You'll probably get a blank screen.
That's a common caveat with any technology that does the error correction for you, by the way, including digital video: it gives a cleaner and more pleasant signal while it does, but will probably give up before you do. So this kind of error correction might not be the best for very long-range flights.

Final word

To appreciate the sheer expanse of outcomes that you might possibly encounter once you start pushing the range envelope, it's probably best to look at ham radio operators.
On one end, they will casually use 50-watt transmitters to just talk locally within a range of no more than several tens of kilometers, and sometimes use kilowatts to punch through unfavorable conditions. On the other end, they can literally talk to the other side of the earth on fractions of a watt and bounce signals off of the Moon. They've been doing all of that crazy stuff for decades and had invented things that were thought impossible.

And the reason for all of those achievements is lots and lots of experimentation. Without testing what works and what doesn't, a theory is useless. So, if you decide to jump down this rabbit hole, start to think like a ham. Make that estimate to the best of your ability, assemble what you think should work best, and then go out and fly it. See how it works in reality, and how it differs from your expectations. Make hypotheses. Go out on different days and in different places to see how the conditions change your outcome. Then change something in your system and see what happens. Write it down. Make your own theory.

And, most important of all,

Have fun!


Wired drone using very high voltage? For those of you who don't know: electricity can be "stepped up" to carry the same amount of power over a thinner wire, over much longer distances with minimal losses. Once the power reaches the destination (like your home), the power is stepped down to a much safer voltage.

Here's what I'm thinking: A quadcopter being powered by a super thin, high-voltage line to continuously hover in a single location indefinitely.
The power cable would be very thin, like 1 mm in diameter.
The voltage would be static-electricity range (very high), but the amperage would be harmlessly low.

When the power reaches the quadcopter, it is stepped down to a normal DC current.

No, I have no plans to actually do this, but how well would this concept work in theory?

Let's work out some numbers.

Picking a DJI Phantom 4 as a 'typical photo drone' example, it's battery is 4s 5350mAh and weighs about 500g, and provides about 20 minutes of flight time.

That implies that the motors are using (5350/1000)x(60/20)=15amps (converting mAh to Ah, and minutes to hours). At 15v that is 225W for flight.

The question talks about using 'static electricity high voltages' - but the most noticeable feature of static electricity is that it can spark across gaps. 10,000v will jump 3mm or so in dry air, and 3000v will jump 0.5mm. However I don't think we need to go that high. Stepping the voltage up 100 times to 1500v would reduce our current to 0.15a.

That means we could use 29AWG wire, which is 0.3mm diameter - at that point the insulation may be heavier than the wire. According to that chart, 29AWG has a breaking strain of 3.6lbs, which is much more than the weight we have saved from the battery so we don't need to worry about the wire breaking under its own weight.

So how long could the tether be? 29AWG weighs 0.3863 lbs per 1000ft (or 175g for 300m). We will need two strands (350g), so 1000ft (300m) of cable uses up most the weight we've saved by eliminating the battery, before adding any insulation or the transformer. 1500ft of wire would be heavier than the battery.

TL;DR:
* yes, you could hover at normal photography drone heights for an unlimited time using a tether.
* The weight of the wire prevents you going much higher than 1500ft.
* The weight of the insulation prevents you using lighter wire.


I'm looking for photo sets from drone photography to convert to 3D models. Where can I find them? I'm looking for photo-sets taken by drones as part of a science assignment to generate 3D Models. Where in the net can I find some sites which can share some samples?

Search youtube for videos with the keywords FPV and ORBIT.  This is the motion that will give you 360 degree frames of an object.  Also search for Point of Interest mode for DJI drones.  Then you can use a youtube downloader service to download the video and then extract the frames you are interested in. Here is an example of a dji poi video https://youtu.be/hlfOVBAmc4o?t=48
If you put -tutorial in your search terms it will weed out all the tutorial videos that you don't want
https://www.youtube.com/results?search_query=dji+point+of+interest+examples+-tutorial


Is there an international competition that yearly chooses the best drones in the world? Is there an international competition that chooses the best drones in the world?

Is there a yearly “Oscar” for drones, somewhere?

If so what are various categories that are listed?

I don't think there is any international competition for "Best Drone". The closest thing to that would be recommendations that experienced pilots make and it would depend on what that person liked.

I imagine that if there was an international "Best drone" competition it would have categories such as fastest racing drone, best freestyle drone, best photography drone, most popular drone, etc.


Is there a method to wire a brushless motor to an ESC so it spins in the required direction first time? So I know that three phase motors will reverse direction when 2 wires are swapped round, or that the direction can be changed in software (such as BLHeli).
But is there a method to get it right first time, without doing something hacky like using alligator clips. Are the wires/pads usually in a standard order on the motors/ESC? Can the phases be worked out some other way?

Without disassembling the motor, and figuring out how the ESC is designed, there is no other way then simply testing it.
From my experience, the motors spinning clockwise has usually been the ones that can be wired without crossing any wires and without having to reverse the direction. But that could just be a coincidence, so you should definitely not trust that it will always be like that, even if that might be the most common.
The simplest and fastest way to get the motors to spin the right way is usually to just solder all the wires so that it looks the best, and then reverse the direction in for example BLHeliSuite as needed.


How to clean a drone? I was just flying my drone when I crashed in some tall grass and there are now a bunch of grass bits all over the drone. How can I clean the drone without damaging it?

I have found that the simplest and probably one of the safest ways is to use a compressor (alternatively a compressed air can will probably work), to lightly blow away the dirt. This works especially well if you just want to get rid of grass straws or similar.

If you want to more thoroughly clean something Joshua Bardwell has a video on how to clean a motor, and if you want to clean a PCB or other electronics, alcohol > 90% and some kind of brush or cotton swab works. And finally, if it's the frame you want clean, soap and hot water works.


How to tune a Deadcat Quadcopter with 10 inch props and asymmetrical mass distribution along the roll axis with a low power to weight ratio? I have a quadcopter with TBS discovery frame and 10inch props running on 810Kv motors on 3S. The quadcopter has an asymmetrical mass distribution since the heavy battery pack at the back causes the weight to be heavily skewed towards the back. The quad is really unstable and a pain to even hover properly, even in angle/horizon.
I was going through another thread on this stackexchange, and was trying with low PIDs to no avail. Turns out I need high PID gain for a craft with low power to weight ratio (around 8 : 3). My tune still seems to have some issues, since my quad was still having oscillations and it suddenly lost altitude and slammed hard into the ground when faced with a sudden gust of wind while hovering at 20m. Doing fast moves like rolls and flips with this quad doesn't really appear to be a good idea before setting up the PIDs properly since it is a bit to large and risky. Most of the tutorials I have followed seem to be stuck on gauging response to sharp turns and pitches and rolls, so I am not sure how to go about it. Increasing I or decreasing P and D makes the quad even not wanting to lift up from the ground, oscillating on the ground like a pendulum along the midline.
This drone is just a hobby project with no special use case. I will be using it just for leisure flying.

The discovery frame uses the old DJI plastic arms and the arms are not very stiff. So you get a lot of flex in the arms. This leads to two major problems: vibrations and the quad has a relative long delay until force of one motor really starts to rotate the quad. This problem gets amplified if you are using out of balance motors or very felxible propellers. This would explain the unstable flight you are describing.
I'm afraid that this is a "hardware problem" and not a "software problem" that you can fix with some PID settings. Modern flight controller firmware is built with certain assumptions about the used frames/escs/motors. A 10 inch prop on a 810KV motor with 3S and a plastic frame isn't a target platform for betaflight or any other race/freestyle oriented FC firmware.
What are your options? Make the frame as rigid as possible and try to dampen the FC so you get rid of the vibrations (e.g. put double sided tape under it). I don't know what FC you are using but try to get some blackbox logs to see the frequency range of the vibrations and try to add more filtering to clean up the signal for the FC. After that you can start to tune the PIDs and maybe get a flyable quad. You can tune the quad without any flips and rolls because with a low power/weight ratio the quad will probably crash in the process. So just tune the quad for regular forward flight.


Remap not yet existing uart I have a flight controller that has one uart to little. So i tried to remap SERIAL_TX 5 (That doesn't exitst on the FC) to pin A09, that previously had SERIAL_TX 1, but that doesn't seem to work. I also tried to remap SERIAL_TX 5 to LED_STRIP, but that didn't work either. Is there something else you have to do to get it working?

The commands I used was:

resource SERIAL_TX 1 NONE

resource SERIAL_TX 5 A09

Serial ports are hardware based, and cannot be remapped. You can however remap software serial ports. Keep in mind not every pin supports softserial either, as an available hardware timer is required. Typically you can use:

UART TX & RX pins
PPM Input pins
LED pins
Motor PWM output pins

If you have one of those free, proceed.

Enable softserial from the Betaflight Configurator "Configuration" tab, then click "Save and Reboot".

Go to the "CLI" tab and type "resource SERIAL_TX 11 A09", hit enter, then type "save" and hit enter.

Go to "Ports" tab and assign the feature you want to "SOFTSERIAL1".

Keep in mind that software serial is limited in terms of how fast it communicate information and the load it puts on the CPU. If you have a very intensive low-latency connection, typically try to avoid use softserial. Softserial is best suited to things like VTX control (smart audio and tramp protocol, etc), GPS, and smart-port telemetry, where latency, speed, or loss of signal during flight isn't an issue. While it can be used for other more system critical links like RC control, I would generally recommend against it, though it is theoretically possible.

Sources:
https://oscarliang.com/betaflight-soft-serial/
http://www.multirotorguide.com/guide/guide-how-to-set-up-the-softserial-uart/


Difference between a 3 and 6 axis gyro When shopping for drones, I see a 3 and 6 axis gyro available, what is the difference between the two? Does one have a advantage when flying over another?

There is actually no such thing as a 6-axis gyro; the correct term for this is "IMU", which stands for "Inertial Measurement Unit". An IMU is a device that combines several inertial sensors that measure the craft's orientation and position in space.

The 6-axis IMU is a composite sensor, which contains two different types of 3-axis sensors on one chip. Usually it is a 3-axis gyroscope (which measures the rate of rotation of whatever it's strapped onto) and a 3-axis accelerometer (which measures its linear acceleration). A 3-axis gyro, on the other hand, is just the gyro and nothing else, as a standalone chip. There are also standalone 3-axis accelerometers¹, but accelerometers are almost never used in flying vehicles alone, without gyroscopes.

The third type of sensor that an IMU can contain is a magnetometer, which measures the earth's magnetic field² and can be used to tell which way is north. A magnetometer can either be present as part of a 9-axis IMU, of another sensor (e.g. in a GPS unit) or an entirely standalone unit.
Do you need the accelerometer and magnetometer? Well, it depends.

For rate mode (or acro mode, as it's more commonly known), the aircraft only needs to know its rates of rotation along all three axes and matches them to the desired rates set by the pilot via stick positions. For this, just the gyro is sufficient.
However, in attitude, angle or autolevel mode (also sometimes called stabilized mode), in which the pilot defines the desired attitude(orientation) relative to the horizon, which the drone will match, a gyroscope alone is insufficient. The flight controller will need to know not only how fast it is currently spinning, but also which way "down" is relative to itself. Due to a phenomenon called integration drift³, the flight controller can't maintain this knowledge precisely enough with just a gyro. It needs an accelerometer on board to correct the gyroscope, so if you want to use these modes, you need both a gyroscope and an accelerometer.
A magnetometer (sometimes referred to as a compass) is required for navigation modes, where besides its attitude relative to the horizon the craft has to also know its heading relative to the geographical north. Note that since navigation modes also require GPS, you could forgo the builtin magnetometer in the flight controller, and get a GPS unit with a magnetometer in it instead. Or you can get both, one in the FC and one in the GPS, which will increase the accuracy of the readings. (actually, you can double the other two sensors for the same effect; some flight controllers are manufactured with a twin IMU for that purpose.)

¹: There are also single- and dual-axis versions of each type of sensor — which only means you'll need several of those to make up a complete IMU. They are rarely used nowadays, as the integrated versions are usually better in every way.

²: Or any other magnetic field, for that matter, which is why you need to keep it away from magnets and steel structures, otherwise you'll get rubbish. There's usually little metal in the air other than what's on your aircraft, though, so magnetometers tend to work quite well in UAVs unless you've got a magnet-latched canopy and put the FC next to it or something. Minimizing interference is also why magnetometers are usually integrated into GPS units and mounted as far away from the rest of the aircraft as possible.

³: Integration drift is an issue that plagues inertial navigation since the beginning of time, and is present everywhere where you can't measure something directly, but you can measure how fast it's changing instead (in other words, you can measure the derivative of that thing). So you integrate it (add up the changes over time) to get the original value. However, every measurement comes with an error, and the errors add up as well, so your total error will grow all the time and at some point it will get bigger than the original thing you were measuring.

Intuitively, integration drift is like walking in a forest. When you enter the forest, you (hopefully) have a sense of which way north (or some other reference direction) is. As you walk, you can maintain a sense of direction for some time ("I was walking towards the north, so it was in front of me, now I turned left, north must be to my right now"). However, since you don't know precisely how much degrees you turned, every turn you make will introduce a small error into your direction estimate, and those errors will add up over time. A couple hours later your sense of direction will have drifted far enough from the original that you might be heading in the opposite direction from where you think you're going. Even if you tried to just walk in a straight line all the time you would probably stray off course eventually, because without external reference you have no way of telling whether you've actually been walking in a straight line (this is known as zero drift).

The only way out of this is to have an alternative source of direction knowledge (e.g. a compass or the combination of the sun's position and time of day, or some other observable directionality in your environment like a distant mountain) which you check regularly and use that knowledge to correct the error in your "internal" sense of direction.

A quadcopter in angle mode has the same problem: to stay upright it needs to know is where "up" is, and a gyroscope can only measure (as an approximation) how much degrees it's been rotated from its previous orientation; it does not know (or care) what that previous orientation was. And even if the FC did know its previous orientation, the estimate might have drifted far off from the original. That's where the accelerometer comes in: its job is to measure the earth's gravity, and therefore the direction of "down", and use that information to figure out the initial orientation when the quadcopter is armed (like knowing where north is when entering the forest), as well as correcting possible drift of the orientation obtained from the gyros in flight.


Questions regarding drone components I am wanting to build an ultra-light manned bi-copter from scratch, but I first must learn about the components, which is why I am here. I am working with a 43kv (24s rated, 192 max Amp) 70kg thrust motor, a 120cm propeller, and a 200A ESC (no BEC). In my research, I have learned that drones additionally need an (U)BEC and a flight-controller board. (U)BECs seem to come in ratings up to 14s.
My questions are:

What (U)BEC should I use?
If I want 30 minutes of flight time, what battery and how many should I use?
What flight-controller should I use?
I plan to have the throttle controlled by a slider on the pilot's control stick. Is this possible?

Thanks!
Edit: Hear are the links to the components I mentioned in the first paragraph:
https://mad-motor.com/product/mad-torq-m40-c30-pro-kv43/#
https://mad-motor.com/product/ampx-esc-200a/
https://mad-motor.com/product/47x13in-uav-drone-prop/

A BEC is simply a way to create 5v power from the much higher voltage batteries. When you know how many amps your electronics can draw, you can choose an appropriately sized BEC.

To run two motors at full power for half an hour you will need 200Ah. The maths is simple, it's just amps * hours. At 24s (90v), that's 18kWh, which is as big as the battery in some electric cars. If you were to use hobby style batteries, you could use 40 of these 6s 20Ah lipos

I don't think I'd recommend any hobby-grade flight controller for a manned aircraft. The FC is flight-critical, if it goes wrong you will crash. Manned aircraft typically have at least three redundant systems, which compare their outputs so if one develops a fault the other two can 'out vote' it. For really important stuff, there is even more redundancy. Needless to say, there's nothing like this in the hobby world.

That should be relatively easy.


Why was 32kHz gyro sampling removed from Betaflight? For a while, the BetaFlight multirotor firmware supported 32kHz gyroscope polling, but now that feature has been dropped in favor of 8kHz being the highest polling rate. Does anyone know why this was removed?

In order to access the 32kHz gyro sampling mode, the gyroscopes in question (e.g. ICM 20689) would be switched to an experimental mode where there is higher gyro data jitter, and that sampling at the lower 8kHz frequency made use of lower overall latency lowpass filtering built into the gyro.
Often to get usable gyro data from the 32kHz sampling rate, more filtering was required, and the overall phase delay response meant that the FC would not be able to start compensating for a change in craft orientation any faster.

The other part is that in terms of pure filtering performance, the net gain achievable assuming identical gyro signal-to-noise ratio performance is on the order of tens of microseconds.  The bigger potential improvement would be to use the higher sampling rate to enable enhanced/fast Kalman filtering where the PID calculations can take into account more data, however, the input noise in that experimental 32kHz mode means the net improvement is minor for the computational cost involved, and that better performance is achievable at the lower sampling rate the IMU units available right now (that meet the cost and form factor requirements to install onto cheap FPV UAS systems)

Practically, lower overall phase delay response with RPM notch filtering and moving lowpass filters well beyond the prop wash and flight input frequency space, which results in much better overall performance, and often reduced motor heat in flight across a wide range of flight envelopes because less amplification of gyro noise is occurring, particularly through the D term of a PID controller which amplifies higher frequency oscillations.


What does the C rating on a LiPo battery mean? I see LIPO batteries specify a C rating on the label.

What does that stand for and how does it affect the performance of the battery?

The C rating is a multiplier that dictates discharge. You can figure out the maximum theoretical discharge by multiplying the C rating by the capacity. For example an 80C, 1300mAh LiPo can output 80*1.3 = 104 Amps. There is no consensus as far as I am aware as to what the letter C stands for.

It is worth noting that C rating is dubious - comparing the C rating between different manufacturers is unlikely to produce useful results as to which battery is better.


I can't bind my S-FHSS Corona SBUS receiver with a jumper t16 transmitter. Are they compatible? It says jumper t16 is S-FHSS compatible. I put my Corona receiver into SBUS mode, but I can't get them to bind. Are the two compatible?

There could be many reasons why it won't bind.  Unfortunately, there doesn't seem to be a clear reason.

Did you follow the binding instructions in the Corona R6SF manual?

http://img.banggood.com/file/products/20160907060650R8SF%20R6SF%20and%20R4SF%20Instruction%20manual%20V1.2.docx

You might also try to upgrade the Jumper T16 internal multi-protocol module firmware.  Here is a link to a video by Joshua Bardwell that outlines the process.

https://www.youtube.com/watch?v=qT_wmbxTBp8


Is it possible to use the head tracking in a FPV goggle with a computer? This might not be the best place to ask this question, but it feels like a good place to start.
There are a few FPV goggles with built in head tracking that sends out a PPM signal. Is there a way to use this together with a computer (for example to emulate a mouse)? As far as I know you would need something to interpret the PPM signal and convert it to a USB signal. One solution / workaround is to connect the goggles to a transmitter and then connect the transmitter to the computer. This, however, feels like a clunky solution and it would be nice with something smaller.

I have an off the shelf PPM to USB adapter. It isn't this one specifically, but works on the same principle:
RC USB-Interface III

You can either wire it directly to an R/C Receiver or to a buddy box barrel connector.
My Fatshark googles have a buddy box output for the head tracking output, which is what I'd typically run into my R/C transmitter. But it should work equally well directly into this.
The difficult part would be remapping the channels. If I remember correctly the buddy box connection gets roll, pitch, and yaw from channels 5, 6, and 7. And the USB device remaps the inputs to appear as a joystick controller with multiple axis and buttons/sliders.


Datasheets for lift of a 27x12x2 inch propeller? I'm looking to find the amount of lift produced by a 27 inch diameter, 12 inch pitch, two-blade propeller spinning facing the ground. Are there any datasheets that show the amount of lift given at any rpm?

There are too many factors to be able to give you a precise plot. All the below have major impacts on propeller performance:

Activity factor

A blade with a thicker chord will generate more thrust, but have less efficiency

Airfoil selection

Prop airfoils change as a function of radius. Some airfoils are good (bad) at low Reynolds and/or low Mach, but are bad (good) at high Reynolds and/or high Mach

Proximity to ground

If you're close to the ground, pushing air at the ground, then you have a good efficiency bump from ground effect.

However, https://www.apcprop.com/files/PER3_27x13E.dat is a good first step. The change in pitch from 12" to 13" is not going to dramatically change matters, and probably has less of an effect than flying in ground effect or airfoil changes.

You can also compare to https://www.apcprop.com/files/PER3_26x13E.dat, which reduces diameter by an inch, while increasing pitch by an inch. You will likely find that a theoretical APC 27x12 will be in between the two in terms of performance.

I hope this is helpful. Ultimately, once you get close enough to your desired theoretical performance there's no option but to try a few blades out for empirical results.


Is there a list of milestones to check off before claiming one can "fly" Is there a generally accepted set of milestones that one should "tick" off before claiming that they can fly ? Are there different guidelines based upon the craft e.g. fixed wings, quadcopter versus helicopter ? Are these published by the modelling associations or by legal bodies like the countries aviation authority ?
My checklist is roughly :

You crash beyond the first patch of khakibos in the veldt we fly in under glide
You crash beyond the second patch of khakibos in the veldt we fly in under power
You crash when you can fly across the veldt, where left is away from you and right is towards you or vice versa, and even return, where left is really right and right is really left and you understand the term "spiral of death"
You crash in style reminiscent of "Those magnificent men in their flying machines" that you feel you could claim was a controlled decent to your friends and family without too much blushing after doing a series of "Uppity up up ups and down di down down downs" (or due to another attack by the resident bully of a hadida)

I doubt this is authoritive in any way whatsoever and was wondering if there was a better set of guidelines to work against.

In the UK, the British Model Flying Association offer an Achievement Scheme which recognises a few levels of competence:

The Basic Proficiency Certificates provide a measure of competence for pilots operating fixed and rotary wing aircraft fitted with
stabilisation technologies.
An FPV extension is also available to holders of any Basic Proficiency or ‘A’ certificate.
The ‘A’ Certificate, which may be equated to a basic standard of safety and flying competence.
The ‘B’ Certificate, which is designed to recognise a more advanced pilot’s increased ability and knowledge, and demonstrates a high level
of safety.
The ‘C’ Certificate, Aerobatics.
The ‘C’ Certificate, Scale
The ‘C’ Certificate, Gas Turbine

As well as covering theory (air law/safety) questions, the flying skill required increases as the candidate progresses through the levels - from assisted flight, through holding level figure 8's and other manoeuvers, to being able to fly in aerobatic displays.


Would the FAA's proposed Remote ID really ground older drones? The FAA has proposed new rules regarding drones, particularly Remote ID

Remote ID would assist the FAA, law enforcement, and Federal security agencies when a UAS appears to be flying in an unsafe manner or where the drone is not allowed to fly.
The development of Remote ID builds on the framework established by the small UAS registration rule (PDF) and the LAANC capability to lay the foundation of an Unmanned Aircraft System Traffic Management System (UTM) that is scalable to the national airspace.

Criticism has been harsh

“Casual drone users would have to establish, maintain, and renew subscriptions just to fly occasionally in their backyards. School programs that use drones may decide the costs are just too high to continue. A gift of a drone on Christmas would saddle your recipient with endless monthly fees. And connecting all drones to the internet would create new cybersecurity vulnerabilities.”

Also

And then there are the technical barriers to compliance. Schulman points out that “thousands of drones and radio-controlled aircraft currently on the market have no means for internet connection and would be grounded.”

Would this regulation really ground all existing drones?

The FPV Freedom Coalition has an excellent summary page at this link.

To sum up the answer to your question as simply as I understand it: older drones that are not able to broadcast their information will NOT be grounded, however they will be required to only fly within FRIAs (FAA Recognised Identification Areas).

Under the current proposal, after one year no new FRIAs may be registered, so as they disappear over time it may become more difficult to legally fly non-compliant aircraft.

I am not a legal expert - if anyone feels my understanding is incorrect then please do let me know.


What does BEC, SBEC, UBEC, and OPTO mean for brushless motor ESCs? I'm looking to purchase an ESC to go with a brushless motor. Many of the product pages include terms related to a BEC, such as SBEC, UBEC, and Opto.

What do those acronyms mean and how should I choose between them when selecting an ESC?

BEC: Battery-eliminating circuit. Basically just allows you to use the ESC to power the controls circuit, servos, etc. (hence eliminating the need for a battery)

SBEC: Switched battery-eliminating circuit. Just an improved version of the BEC which makes it more energy efficient.

UBEC: Similar to SBEC, just more energy-efficient at the expense of being slightly heavier.

Opto: Uses light (optocoupler) to segregate control and motor circuits, to reduce interference. Therefore requires two sources of power, one for the controls and one for the motor.


How do I successfully stabilize or trim a TinyWhoop Nano? I'm a newbie to drone flying and decided to start with a TinyWhoop Nano RTF. I know just enough about model aircraft controllers from using them in robotics and animatronics that fine-tuning is necessary to get stable or centered actuators.
In the case of the Nano, I am not sure about the right procedure to trim out the rotors. My expectation was to get it to hover and then use the trim buttons to get it to stop drifting in a particular direction. It would usually drift and hit something before I could manage to figure out what direction needed to be trimmed. I finally put it in a very large open-top cardboard box to stop having to chase it all over the room.
I've gotten it to drift much less, but it still seems to be all over the place when I throttle up more. I've had problems with one of the props scraping the canopy ever so slightly, which is annoying thing to try to fix.
So I guess my question is twofold:

What's the specific method to trim a TinyWhoop Nano using the TBS controller that comes with the RTF version; and,
Is there a general process for trimming out any new quad, such as how much throttle to use and a clean environment in which to more carefully check it?

Often the really small/simple drones don't trim to completely stable, as their controllers are very basic and the 'step size' on the trim isn't fine enough. And, if you get them to trim, then they will usually drift again as the battery voltage changes - again, due to the simple design.
I usually just get it as close as possible, and accept there will be drift - its good object avoidance practice.
Finally, a tip - if such a small drone is going to crash, just stop the props ... this usually results in less (if any) damage to the drone or whatever it hits.


Will this set up fry my components? Frame: Carbon fiber 250mm
Motors: 2300Kv 2204
Power board: Matek built in BEC’s 12V + 5V
FC: CC3D
ESCs: HLGRC 30A opto (no BEC)
Battery: Turnigy Graphene 14V 75C 4S
Receiver: Turnigy iA6B
My question is, this is the first time I’ll be using the opto on a drone. How do I power the FC without frying it, seeing as how there are no BECs on the ESCs?

The Matek PDB has a 5V regulator and this can be used to power the fc.
Just wire the PDB to one of the unused ESC plugs on the FC. The FC has solder pads for 6 ESCs (right on the picture) and for a quad you usually only need 4. So the connectors 1-4 are used for the escs and you can use 5 or 6 for the PDB.
The center pin (with + above) is 5V and the outer pin is ground (- above). Connect these two pads to the according pads on the PDB.


How to measure the pitch of a propeller? I have some random drone propellers which I don't have any information on. I looking to find a way to measure the pitch of the propellers to figure out if they will be well suited to a 5-inch drone I have. Is there any way to go about measuring prop pitch? (at least somewhat accurately)

Theoretically the pitch of a prop is supposed to be the distance it would move in a full rotation (in an ideal world).

As most modern props vary pitch along their length, a single number is almost impossible to measure. Manufacturers tend to give a number which is an indication of how the user would expect the prop to perform.

Most propellers will work on any 5" drone, they usually have the pitch printed on the upper surface of the blade near the leading edge.


Video is lost after crashing This problem started a few days ago. After crashing with my quad I almost completely lose the video feed until I power cycle the drone. The only time I have video is when I get really close to the drone (Less than 1 meter), so it almost seems like the VTX enters pit mode when the crash happens.

I have pit mode on a switch, so I have tried turning it on and off again, but that does not help. It also seems like I can't enable pit mode at all (only disable. It is on when powering on), but that might not be relevant to this.

The VTX I'm using is the TBS UNIFY PRO 5G8 HV - RACE

Even if the antennae didn't feel loose, it probably was. After removing and screwing it back in I haven't had this problem again.


What's the advantage of props in VS props out? I've heard that the quad will handle better if you reverse the propeller direction (props out), but is the difference noticeable? Especially for a relatively new pilot. Should you use props out from the beginning if you aren't used to one or the other yet?

Are there more advantages, and are there any disadvantages?

Lastly; why have props in become the standard if props out seem to be better?

As far I know the only difference is on the whoops. They fly much better on props out.
On 2,5-5 inch quads, it doesn't matter. Props in: our camera is dirty, you can stack easier on the tree. Props out: Your flight controller is dirty and then you damage your prop it's a higher risk that pice of the prop damage your flight controller or battery (it is a much higher risk).
Greatings form DE.


Difference between analog and digital FPV systems? The new DJI digital FPV system and a few other systems are using a digital signal for FPV video. How is this different from a traditional analog signal for FPV drones?

tl; dr:

Analog is:

Cheaper;
Lower resolution;
Has a noisier, more staticky picture that breaks up gradually when the signal gets weaker. Analog image breakup, while unpleasant to the eye, is generally easier to see through.
Has a constant low latency;
Is an entirely open standard, with anyone free to produce compatible equipment

Digital is:

Currently rather expensive,
Has (significantly) higher resolution,
Has a way cleaner image, usually without a speck of static right up to the very limit of its range, but when it starts breaking up, it does so suddenly and in weird ways. The broken image is usually harder to see through than an analog signal. With DJI, for instance, the picture will suddenly get very blocky and low-res when it gets out of range.
Also, digital systems can have inconsistent latency that changes in flight (DJI in particular is known for this), although this mostly concerns the highest-performance pilots, such as racers.
The only digital system currently in widespread use is the DJI system, which is a proprietary standard with only two manufacturers authorized to make the gear.

Analog and digital systems have about the same usable range per unit of VTX power.

To compare how they look, it's better to just see the videos:

DJI HD system range & breakup vs analog
ByteFrost image & breakup

How they work and the reasons for noise/breakup related differences:

Anything that is encoded in a radio signal at a point in time can be represented as a level, which can be higher or lower; Thus the "primary" information encoded in the signal can be represented as a graph of this level over time:

In an analog system that level can take any value, within some range, which we'll think of as 0 to 100% for simplicity(*). It can be 20%, 70% or 48.573498%, theoretically to any degree of accuracy. The drawback to that is that any noise that's floating around in the radio spectrum will add to whatever signal you're receiving, so in practice, you'll get something like 40% (true signal) + 5% (noise) = 45% (received signal), and since the original signal could be anything, the receiver has no way of knowing which part of what it got is noise.

The image that your goggles receive is made up of pixels, and the color that each of them has is encoded as percentages of red, green and blue: zero to 100%. An analog TV system encodes this picture by "scanning" over all of the pixels in sequence, line by line, and setting the signal's level equal to each pixel's brightness in turn. For example, this oscilloscope picture represents the TV signal for the "colored bars" picture:

The ladder you see represents how the brightness level of the pixels changes from left to right in each line of the image.
There are also other signals overlaid on top of it, these correspond to the lines closer to the bottom of the image, which have other sequences of colors in them (the oscilloscope displays all the lines together on one screen).

The consequence of all that is that whenever there's another signal on your frequency around, it gets added to your VTX's signal and through that directly to your picture. Since usually that other signal is noise(**), your picture is overlaid with noise.
When your signal is strong, the noise is a very small percentage of it and is usually unnoticeable by the eye. As the useful signal gets weaker, though, the noise (which stays the same) will get stronger compared to it, so the percentage of noise in your picture increases. At some point, it will become so strong that you couldn't see any useful signal in the picture anymore.

In a digital system, however, only two levels are available: 0 and 1, represented by 0% or 100%(***). The image is encoded into a sequence of bits using a special algorithm, called a codec, and decoded from that sequence on the other end, almost exactly like online video. Besides simply encoding the video feed, one of the most important functions of modern codecs is to compress it, so that it can be communicated in a significantly smaller amount of bits, which in turn means that higher-resolution video can be transmitted with the same bitrate (number of bits sent per second).

Since radio signals are by their nature analog, on the receiving end noise will still be added to the signal, so if a 0 was transmitted and 10% of noise is added by the environment, the received result is 10% — but since the receiver knows that only either 0 or 100% could have been transmitted, it picks the closest possible level, in this case, 0.

This means that when you transmit digital data, noise is just ignored until a certain point: Even when noise levels are as high as half of the analog signal (which creates a picture that's rather hard to parse), with digital you receive exactly the same information as you would if there were no noise, with the resulting video perfectly clear. However, when the relative noise level does pass the critical threshold, ones will start suddenly (and randomly) becoming zeroes and vice-versa. What happens to the video after that depends on the particular digital system and how the video is encoded in it.

With the DJI system, the whole screen suddenly becomes low-res and blocky, occasionally skipping frames, and the latency increases. The cumulative effect of this can range from "just an unpleasant-looking image" to "totally unflyable".

With Fatshark's Bytefrost system (currently in development/beta testing), random bits of the image will flash with colored blocks, while the rest remains high-resolution. The manufacturer touts this "analog-like" style of image breakup as a feature of the system.

In both cases, digital breakup, when it does happen, is arguably harder to see through than analog breakup, because our brain still has better error correction software than seen in these systems. This is also due to the fact that digital images, while crystal clear up to a point, start breaking up sharply after that point and quickly get to "very hard to parse" levels, while an analog picture is already quite static-ridden by then and just continues to gradually get worse.

That said, digital systems can employ error-correcting codes and other tricks to be able to recover from a certain percentage of errors, at the expense of reduced bitrates, yielding a lower-quality image which can be decoded from a longer distance.  you'll typically see them start to gradually reduce image quality before breaking down completely, giving you some warning signs that you are going out of range. There is also usually a link health indicator somewhere in the corner that is similar to the RSSI reading for RC control systems which you could look at to see if you're going out of range. You probably aren't going to be looking at it all the time, though, and a low signal indication can be missed, while it's hard to miss an image full of static and getting worse.

Footnotes:

(*): The analog signal can technically be any real number, and can sometimes go beyond its designated range, i.e. in our example be less than 0 or bigger than 100%. How the system handles the signal going out of its designated boundaries is the system's business.
(**): the other common kind of interfering signal is your own signal that's reflected off of something. In which case you will get two of the same picture overlaid on top of each other, but one of them which is slightly late and is shifted to the right because of that. This is called multipath interference, or multipathing, and is a major source of image degradation with analog FPV systems. Cutting down on multipath signals is also the primary reason why circular-polarized antennae are used in FPV..
(***): Actually, a digital system can have more than two values, and there are different ways of representing them as analog levels; the main distinguishing factor is that there's a fixed (integer) number of them. For example, for a simple digital system with 4 levels, they would be 0, 33%, 66%, and 100%, with corresponding ranges of -∞ to 16%, 16-50%, 50-83%, and 83%-∞.


On a multirotor, how effective is braiding of power wires from the ESC to the BLDC Motor(s) in reducing or eliminate emf? Assuming BLDC motors with the ESC positioned at the 'worst case' (furthest distance) with longest power wires between the ESC and the motor, will braiding these three wires reduce the EMF that would be produced by unbraided wires? Or, would shielding these three wires work better? Is it even needed if the wired are inside a carbon fiber strut? After all, the CF is conductive and will act as a shield against EMF.

The braiding of motor wires should only be done for looks.  It looks cool and that's about it.  It may actually cause problems with smaller motors.  I once had braided motor wires on a brushless whoop size quad and the braiding of the wires caused the motors to behave erratically at start up.  Sometimes they would start spinning.  After removing the braids they started up perfectly every time.


Drone simulators for designing and flying aircraft? Is there any free software that can design drones/aircraft and test fly them? Thank you. I’m looking for a software with no controller needed, just to test if the aircraft/drone can hover with stability.

I am not quite sure what kind of drone you'd like to build. However, here are the ones I use for a variety of multirotor and fixed-wing drones:

I love CoppeliaSim (formerly V-REP) for multitorotors. It makes it very easy to make certain assumptions about forces and torques, and to see the results in real-time.
X-Plane is great for fixed-wing drones. X-Plane simulates flight dynamics on a fluid-dynamics level so it's actually simulating the plane as it would fly based on its geometry.


For custom multirotors, what is the most useful method of collecting flight data? When it is desirable to know exactly what is happening on a multirotor, such as when flight testing a new multirotor concept or design, what measurement equipment and circuit designs are most useful and most commonly used? Are there stock products? Do they record everything on an on-board memory card like a 'flight recorder" or do they transmit the data back to a ground station for display and recording?

If you're using a flight controller running either the Cleanflight or Betaflight firmware, you can make use of the builtin "Blackbox" logging features. These firmwares rely on the flight controller to have a MicroSD card slot which you can populate or an onboard flash chip to save the flight data to.

In order to configure the flight controller to use Blackbox logging, you'll need to go into the Betaflight/Cleanflight Configurator app and follow the steps of this tutorial.

After you fly around and get back to your computer, you'll want to download the logs and view them. If you recorded to a flash chip on the flight controller, you'll need to use the Betaflight/Cleanflight Configurator app to pull them off, but you can also just pull the SD card out of the quad and put it into an SD card reader if you used the SD card slot.

Then, you can view and process the logs using the Betaflight/Cleanflight Blackbox Viewer app. Joshua Bardwell on Youtube has an excellent video playlist discussing how to analyze them, as well as Mark Spatz from UAV Tech. The UAV Tech channel is an excellent resource for this kind of technical analysis.


Beeper beeps if transmitter is turned of even if it shouldn't I have turned off all beeper sound signals in Betaflight Configurator, but the beeper still beeps if the transmitter is turned off. I thought that that shouldn't happen when RX_LOST was turned off or not paired, but maybe I have understood it wrong? Or is a bug or a problem with my setup in some way?

Here is my diff all:

#

# diff all

# version
# Betaflight / STM32F405 (S405) 4.1.5 Mar 16 2020 / 05:19:58 (d4e74e39c) MSP API: 1.42
# manufacturer_id: AIRB   board_name: OMNIBUSF4SD   custom defaults: YES

# start the command batch
batch start

# reset configuration to default settings
defaults nosave

board_name OMNIBUSF4SD
manufacturer_id AIRB
mcu_id 003c00403436511339373635
signature

# resources
resource SERIAL_TX 1 NONE
resource SERIAL_TX 11 A09

# feature
feature SOFTSERIAL
feature TELEMETRY

# beeper
beeper -GYRO_CALIBRATED
beeper -RX_LOST
beeper -RX_LOST_LANDING
beeper -DISARMING
beeper -ARMING
beeper -ARMING_GPS_FIX
beeper -BAT_CRIT_LOW
beeper -BAT_LOW
beeper -GPS_STATUS
beeper -ACC_CALIBRATION
beeper -ACC_CALIBRATION_FAIL
beeper -READY_BEEP
beeper -DISARM_REPEAT
beeper -ARMED
beeper -SYSTEM_INIT
beeper -ON_USB
beeper -BLACKBOX_ERASE
beeper -CRASH_FLIP
beeper -CAM_CONNECTION_OPEN
beeper -CAM_CONNECTION_CLOSE
beeper -RC_SMOOTHING_INIT_FAIL

# map
map TAER1234

# serial
serial 0 64 115200 57600 0 115200
serial 2 2048 115200 57600 0 115200
serial 5 16384 115200 57600 0 115200
serial 30 32 115200 57600 0 115200

# aux
aux 0 0 0 1700 2100 0 0
aux 1 1 3 1300 1700 0 0
aux 2 13 2 1300 1700 0 0
aux 3 35 2 1700 2100 0 0
aux 4 36 1 1700 2100 0 0
aux 5 39 3 900 1300 0 0

# rxrange
rxrange 0 987 2011
rxrange 1 987 2011
rxrange 2 987 2011
rxrange 3 987 2011

# vtxtable
vtxtable bands 6
vtxtable channels 8
vtxtable band 1 BOSCAM_A A FACTORY 5865 5845 5825 5805 5785 5765 5745    0
vtxtable band 2 BOSCAM_B B FACTORY 5733 5752 5771 5790 5809 5828 5847 5866
vtxtable band 3 UNKNOWN  U FACTORY    0    0    0    0    0    0    0    0
vtxtable band 4 FATSHARK F FACTORY 5740 5760 5780 5800 5820 5840 5860    0
vtxtable band 5 RACEBAND R FACTORY    0    0 5732 5769 5806 5843    0    0
vtxtable band 6 IMD6     I CUSTOM  5732 5765 5828 5840 5866 5740    0    0
vtxtable powerlevels 2
vtxtable powervalues 0 1
vtxtable powerlabels 25 200

# master
set gyro_sync_denom = 2
set dyn_notch_range = LOW
set dyn_notch_width_percent = 0
set dyn_notch_q = 200
set dyn_notch_min_hz = 90
set acc_trim_pitch = 4
set acc_trim_roll = -6
set acc_calibration = 40,-16,-19
set min_check = 1010
set max_check = 1990
set rssi_channel = 9
set serialrx_provider = SBUS
set dshot_bidir = ON
set motor_pwm_protocol = DSHOT300
set vbat_scale = 108
set small_angle = 180
set pid_process_denom = 1
set osd_rssi_pos = 2426
set osd_rssi_dbm_pos = 120
set osd_tim_2_pos = 2455
set osd_flymode_pos = 2401
set osd_current_pos = 2440
set osd_mah_drawn_pos = 2448
set osd_warnings_pos = 14602
set osd_avg_cell_voltage_pos = 2433
set osd_flip_arrow_pos = 2095
set osd_stat_max_spd = OFF
set osd_stat_battery = ON
set vtx_band = 1
set vtx_channel = 1
set vtx_power = 2
set vtx_freq = 5865
set vcd_video_system = NTSC
set gyro_1_align_yaw = 2700
set gyro_rpm_notch_harmonics = 1

profile 0

profile 1

profile 2

# restore original profile selection
profile 0

rateprofile 0

# rateprofile 0
set roll_rc_rate = 90
set pitch_rc_rate = 90
set yaw_rc_rate = 90
set roll_expo = 35
set pitch_expo = 35
set yaw_expo = 35
set roll_srate = 80
set pitch_srate = 80
set yaw_srate = 80

rateprofile 1

rateprofile 2

rateprofile 3

rateprofile 4

rateprofile 5

# restore original rateprofile selection
rateprofile 0

# save configuration
save
#

After making sure that you have the RX_Loss beeper disabled, the next port of call would be to check your DShot config.

It may not be the beeper that is making the noise - there is a DShot beacon configuration that allows you to set your ESCs to beep in the case of RX_Loss  - Id recommend you make sure you have that setting correct.

Edit: from your Diff All, it seems that beeper on RX_Loss May still be turned on, though I’m not sure.


Where can I find a computational fluid dynamics model of a full quadcopter or multirotor? I have searched for any computerized graphics visualization of a quadcopter or other multirotor and all I am able to find are a very few models of a single propeller. (Simscale has an example of a single quad arm and rotor here:) Has anyone seen a full multirotors visualizations produced by computational fluid dynamics (CFD)? NOTE: I am not looking for a schematic animation. Those are abundant.

You can make your own using free software.

Let’s take Fusion 360 as an example, in its simulation suite it has a Computational Fluid Dynamics study option.

If you’re willing to design an accurate-ish model of the aircraft you want, or pay someone to design one for you, you can run the CFD simulation and get the results for yourself.

This is obviously CPU intensive so there is an option to run it in the cloud on Autodesk’s servers.


What type of connector is used on the DJI manifold 2? I'm looking for a certain connector's specification that is used in the DJI Manifold 2. Unfortunately, there is no information about this connector's specifications in the data sheet, it only talks about the communication port.
Could somebody help me?
I need to know what the connector's specification is to buy for my search.

RJ-45
USB-A
HDMI
Antenna ports
connector XT-30
Power indicator
USB micro B
UART PORT, what is connector specification?
CAN PORT, what is connector specification?
I/O PORT, what is connector specification?

Based on some searches, I think this connector is purposely undocumented as DJI states clearly on sites that sell the official cable:

Note: Only use a DJI UART cable such as this one to connect your own device to the Matrice 100's UART port, as other cables can cause the flight controller or your device to be damaged from excess voltage.

In any case, I think I've figured it out. Using this image:

And the dimensions from the manual:

I was able to establish that the connector pitch is probably 1.25mm. I use a lot of JST brand connectors in my work, and I think the GH series are a spot-on match:

Based on this, the connectors would be part numbers:

4-pin header (device socket): SM04B-GHS-TB
4-pin housing (cable end): GHR-04V-S
10-pin header (device socket): SM10B-GHS-TB
10-pin housing (cable end): GHR-10V-S
Contacts (crimp pins): SSHL-002T-P0.2

This is only a best-guess and I must reiterate once again that DJI does not appear to support nor endorse third-party cables, let alone DIY solutions.


27+ inch racing propeller suggestions? I'm looking for some propellers that can handle high rpm (7000-9000) and are large in size. (27+inches length) (pitch: 15+)
Any suggestions?

I don't think what you're asking for exists. There just aren't many props even available in that size. T-motor and Xoar both have props in that diameter range, but most of them are lower pitch around 8ish for that diameter. You could potentially use an airplane prop, but not sure if you could get the reverse pitch prop easily. My guess is you'd have to have something custom made.

Check these links for some commercially available options:

http://www.helipal.com/index_tag.php?tags=Industrial,Drones,Propellers&tags_type=Products%20Type,Parts,Accessories,Features

https://www.getfpv.com/propellers/commercial-industrial-propellers.html

And it looks like this company can create custom carbon fiber props to spec: https://www.mejzlik.eu/

It's also worth noting that a 27" diameter prop has a maximum RPMs of about 7700 RPM. You can't run a prop higher than about 0.8 the speed of sound without the prop essentially tearing itself apart, especially with these larger props. You can use this calculator to plan the exact target RPMs.  Keep in mind though, even reaching 80% the speed of sound takes a huge amount of power, and there may not be motors large enough to dissipate that kind of wattage. You'll probably have to end up settling for an RPM target a bit more reachable.

If you're looking at transonic or supersonic propeller designs, you're looking at a completely different system approach in both the motor and power system, and normal commercial/hobby grade components are not going to be suitable. I'd look towards custom engineering and development through a contractor with specific experience in that area.


Is superglue (cyanoacrylate) a viable means to repair quadcopter frames? One of the tiny struts holding the rotor on my TinyWhoop Nano broke (surprise!) and I've used superglue (cyanoacrylate) to bond it back together. I don't know yet if this fix will be suitable or not, because I haven't even gotten the quad properly flying.
As fragile as some small drone frames seem to be, I wondered whether it's possible to glue them together, or if there's irreversible damage due to having the angle of a rotor changed slightly.
I know some frames are carbon fiber and I wouldn't expect superglue to work well.
Is it a "standard practice" to repair minor damage on frames, or is it recommended to always get a new frame should non-superficial damage occur?

It depends on the risk you are willing to take, but for such a small drone being flown indoors I'd give it a go1 and accept it may crash - after all, it has already done so once so it can't be made worse! The repair will, however, be a weak point in future crashes.
How well it flies will depend on how accurately you reposition the part, but you're likely to get 'close enough' (again, probably 'worth a try'.) I would also, once the glue has fully set, try to hold the drone only by the broken bit and give it a shake - if it can hold the whole weight, it should be OK when the weight is divided between the propellers.
For larger drones you should replace the part to manufacturer specs or get a professional to take a look.
1 Subject to the normal indoor flying considerations - avoid pets, other people and anything expensive or valuable, etc.


Why do drone propellers have blades with thin chords? Almost all propellers used for drones have very thin chord length compared to the propellers used for things like table fans or boats which seem to have blades with much longer chord length. What is the reason that drones most often use propellers with blades that have thinner chord length?

Common drone propeller shape:

Common table fan or boat propeller shape:

Overview

The most efficient propeller is single bladed, has infinitely narrow chord, has infinitely thin airfoil, has an infinitely long blade, spins infinitely slowly, and requires infinite torque. So at the risk of stating the obvious, propeller design is a study of the tradeoffs and compromises required to make something practical. Here's a list of some compromises:

length: landing gear height (or water depth) restricts how long a blade can be.
material constraints: thicker airfoils resist forces better. Stronger materials allow for thinner airfoils while still meeting required blade strength
power-plant constraints: the torque required to spin the propeller should match the motor/engine's efficiency and power curves.
number of blades: more blades equal more thrust for a same diameter
increased activity factor (aka blade width): wider blades produce more thrust for the same diameter
balancing: one prop is very hard to balance without causing lots of drag by the opposing mass.
vibration: three props give fewer vibrations than two
sound pollution: smaller props spinning more slowly are more pleasing on the ear
consumer perception: consumers like to see big blades in their fans, regardless of real-world efficiency and performance.
density of the fluid:

dense fluids such as water can cause cavitation, which can quickly  damage the propeller. One solution is to change tip shape so as to minimize cavitation likelihood.
on the opposite scale, with low-density fluids such as air, the blade tip can spin so quickly it stalls.

As it relates to drones

Rotorcraft are a little special, so let's break out by type:

Vertical propulsion

Multirotor drones and helicopters have tons of space compared to boats, and so don't particularly need to restrict their diameter. They choose their rotors based primarily on power-plant performance.

Longitudinal propulsion

Fixed-wing drones with landing gear obey the same rules as full-scale aircraft. If  the prop is going to hit the ground on takeoff it's not very useful!

Fixed-wing drones without landing gear, e.g. hand-launch gliders, can use very large folding propellers. These are chosen similarly to multirotors, where it's about efficient power-plant matching.

As pointed out by @RobinBennett, "You don't want it stalled when the aircraft is stationary, so there's a maximum pitch angle - and that sets the maximum speed. If you want to go faster you need to spin the prop faster, and if you've got a fixed amount of power, you need a smaller prop just to spin it faster."


What is a "mushroom antenna"? In Can circularly and linearly polarized antennae be used together for FPV? I read about a "mushroom antenna". While I have very little experience with FPV drones I am generally experienced in radios and I had not heard of such a thing, so my curiosity was piqued.

Searching the cybernets, I'm able to find a great many of these antennas, largely low cost devices aimed at the FPV market. But I was unable to find any engineering information, such as the details of their internal construction or radiation pattern.

So what precisely are these antennas? Do they have a particular construction or will any antenna inside a mushroom-shaped radome do? Are there any available technical documents which show their radiation patterns, either through simulation or empirical measurements?

A "mushroom" is just a clover-leaf antenna. Generally they have a plastic cover that makes them look like a mushroom, hence the name.


What are the exact specifications of a RushFPV SMA connector? I am designing a mount for a RushFPV SMA connector and have not been able to find the technical details.

I need:

The diameter of the connector

The distance between the mounting screw holes

The dimensions of the mounting plate in which the holes are cut.

If anyone has this information, I would be very grateful.

Thanks.

The Rush cable is slightly non-standard as it lacks the threads on the holes that the TBS connectors have. It works fine though. The SMA is a standard SMA thread, so the normal hole size for SMA connectors works well. In my designs I usually use a 6.5mm hole for SMA, though some of that depends on the tolerances you're dealing with on your machining. The hole spacing for the small mounting holes is 11.5 mm from center to center. I usually use a 1.5mm hole for the bolt for the Rush SMA mounts, as you can thread an M2 bolt right into the carbon without needing an additional nut, but if you're wanting to use a nut, you'll want to increase that to a 2mm hole.


What do I need to do to get OpenTx 2.3.X to include D8 on a Taranis QX7 model? I'm trying to do away with swapping my multiprotocol module and CRSF Micro TX unit, and have some D8 receivers that can arguably do the trick, but I haven't had any success with this after flashing up to OpenTX 2.3 (the first nightly than enabled CRSFShot).

To clarify - this is an ACCST (non-ACCESS) QX7, running FCC Firmware on FCC flavored receivers.

This depends on your version of QX7.

If it is ACCESS, then, as far as I know, there is currently no way to enable D8.

If it is ACCST FCC, it should already have D8 enabled by default, so it is unlikely to be this model.

If it is ACCST LBT, then when updating the radio, when selecting the features, you can enable D8 mode by selecting the appropriate checkboxes as shown in this video by Whirly Bloke: Video


FS RX2A Pro Receiver Not Working I'm building a drone for the first time following the Prusa tutorial (https://blog.prusaprinters.org/how-to-build-a-3d-printed-micro-drone/) but couldn't get the RC receiver to work. I got my receiver from here (https://banggood.app.link/f7SKbZC5I5) and I'm using the HGLRC XJB F413 board.

I've binded the receiver to the controller and soldered the positive and negative wires to the board. Left the remaining two wires (one yellow, one light brown) cause I wasn't sure which they are (one is SBUS and one is PPM but not sure which is which). I first connected the board to Betaflight and set it to PPM. Tried connecting one of the wires and was able to get readings from controller. Then I set Betaflight to SBUS and connected the other wire but couldn't get any readings out of it. I tried a few more times with both PPM and SBUS but it just stopped working. After a few trials the receiver stopped beeping and light up when I connected the battery and its temperature became very high within a few seconds.

I initially thought I either shorted something when I was figuring out which wire's which or the receiver was defective so I purchased another one but the exact thing happened again. So I was wondering if anyone knows what's going on here and if there's anything I can do to get it to work? Thanks in advance.

You mentioned that you tried SBUS, but that receiver only supports PPM and IBUS (not SBUS).  Try setting your flight controller to use IBUS.  As for the RX getting hot - I'm not sure about that.  The photo on banggood shows that it takes VCC, but be careful.  The description details indicate that it only accepts 3.3 - 5 volts for voltage.  If your using anything more than a 1S Lipo, you will certainly fry the RX unless you have it soldered to either a 3.3V or 5V pad.

Here is the protocol and voltage information from Banggood.

Signal output: IBUS, PPM

Power input: 3.3-5V


What mission planner should I be using for INav? I'm new to the quadcopter community and am looking to plan my first mission for my drone.

As far as I can tell, the recommended mission planner is an Android app? I am hoping there is a good alternative to this for INav.

I just want to check it can leave the ground with a simple hover at 1m and land?

This is the official recommended mission planner for INav on the Google Play Store:

https://play.google.com/store/apps/details?id=com.eziosoft.ezgui.inav&hl=en

From the official GitHub repo:

  Mission Planner for INAV can be downloaded from the Google Play Store. There is a free version which limits number of waypoints to 5 and (very reasonably priced) paid-for version with additional functionality. The application is not open source. For questions and help the RCG "Mission Planner for INAV" thread can be used: RC Groups support forum.

There used to be an app for iOS as well, but this is no longer available on the app store.

Another app for Android is Droid Planner 2:

  Droid Planner 2 can also be downloaded from the GitHub. It is free and released under GNU Public License v3.

  Droid Planner only supports iNav's one-way MAVLink protocol. The following telemetry data is displayed:

  Vehicle position on map, active flight mode, heading, altitude, speed.
  A broken connection recovers once restored after any amount of time. The flight track remains on screen even when data link is broken -> lost model recovery. Log files can be opened in PC software Mission Planner.

More options can be found in the GitHub repo.


How to use an XM+ receiver without a flight controller? All of the model aircraft I have seen without flight controllers normally have a receiver with all of the channels separate. Is there any way I can use a receiver like an XM+ receiver on a model aircraft without a flight controller?

Yes, you most certainly can. The device you will need is called an SBus Decoder, which splits the SBus serial signal from your FrSky XM+ into several different PWM channels.

Example of an 8-channel SBus decoder
Example of a 16-channel SBus decoder


How to determine the lowest safe ESC current rating for a drone build? I was planning to build a quadcopter and was wondering how I should decide what ESC to get. I'm asking about ESC current ratings. I am building a 7 inch drone using 4s with 2306 1900Kv motors. I have seen ESCs ranging anywhere from 25 amp to 50 amp frequently used on 4s quadcopters. I am looking to get the lowest amp ESC that will work for my drone because of cost.  Are there ways to figure out the minimum ESC amp-rating that will work safely for my drone?

I think most people just copy other builds, and step up a size if they burn out any ESCs.

If you want to be more scientific you could test one motor with a watt-meter to measure the current draw. Throttle up slowly so you can watch the current build, to protect the ESC you're using for the test. Also check the motor temperature after 30 seconds or so.

This will give you the maximum current that each ESC needs to handle.

There are lots of different designs of watt-meters available for hobby use. They typically measure up to 100amps so should all be adequate for this test, and cost less than a set of ESCs.

A typical multi-meter will only measure up to 10amps and would not be adequate. Clamp meters typically only measure AC current, and we need to measure the DC current from the battery to the ESC.

Fix the motor to something solid, like a plank of wood that is clamped to a bench. Be careful that the wires and other loose material will not be sucked into the prop, and don't stand in-line with the prop, just in case breaks and throws the blades out at high speed. Even a couple of hundred watts is quite intimidating in a bench test.

Alternately, you could search the forums to see if anyone else has tested a similar motor with a similar voltage battery and prop.


How to recognize damaged brushless outrunner motors? I would like to know how to recognize damaged brushless motors on a drone? What are the most common symptoms?

There are many signs that a brushless motor is broken or getting worn out. Something that can happen to motors that have been used for a long time is their bearings wear out. If you notice that the bell of a motor feels loose or the motor is excessively noisy or has a grinding sound, it is likely worn-out bearings. You can either replace the bearings or buy a new motor.

Another thing that happens is the magnets can demagnetize over time if the motors get hot. A way to know if this has happened is to run the motor with no load. If the RPMs are unusually high, the magnets are likely losing their strength. In this case, you need a new motor.


LiPo battery power maximization I have a 3S1P 2.2A 50C battery for a drone that I build. I have a charger that looks like this:

https://www.alibaba.com/product-detail/RC-B3-AC-Lipo-Battery-Charger_60812527463.html
At first, when the battery was new, I pulled a solid 15-20 minutes of aggressive flight time but now, only 6 months later, it is getting only 3 minutes! I have charged it for like 5 hours and it reached 12.48 volts which is good but I think the charger doesn't put much current and when it hits 12V it just stops charging. This is just a guess. Can someone please help me with this. I don't have much of a budget so is there is a safe way for me to get more flight time, I am more than happy to hear it!
Specs:
My drone is an F450 frame with 4 A2212 100kv motors and weighs a total of 4lbs. My props are 1045 props and I have 3S 30A ESCs! I am using an Arduino as a flight controller and the YMFC-AL firmware/code.

TL;DR:
You probably need to get a new battery pack. Your current one is likely at the end of its life.

My guess is that your battery is just old and has reached the end of its useful lifetime. The fully-charged capacity, and by extension flight time, of all batteries decreases over time when charged and discharged repeatedly. This process is sped along by pulling large amounts of current from the battery like what is sometimes necessary for multirotor flight.
Your description of the slow charge rate after the battery reaches ~12V points to the battery being degraded. At 12V, a 3S battery pack is sitting at ~4.0V/cell. This means that the charger has likely entered the balance charging phase where it tries to equalize the voltage of all 3 cells in the pack and slowly bring them up to 4.2V/cell.
Well-worn batteries will take longer in the balance charging phase because the internal resistances of each cell in the pack (which generally increases during the battery's lifetime at different rates for each cell in the pack) are different, resulting in more energy and time that must be used to fully balance the pack.
Tips for Increasing the Lifetime of a LiPo Battery
Although you mentioned that you're not really on a tight budget, you're probably interested in how you can make your next battery packs last longer. Here are some of the more common things that cause wear:

Sustained and peak current draw:
It's generally an excellent idea to avoid drawing excessive amounts of current from a battery. Full throttle punches are fun and sound amazing, but do contribute to accelerating the degradation of the battery, so maybe don't do them as often. :)

Charging beyond 4.2V/cell:
LiPo batteries shouldn't be charged beyond their full capacity of 4.20V/cell. Aside from increasing the risk of spontaneous combustion, the increased cell voltage puts extra strain on the internals of the battery, which accelerates battery degradation. It's true that some specific variants of LiPo have higher full-capacity voltages, like LiHv with ~4.25V/cell, but the vast majority of LiPo cells shouldn't be charged beyond 4.20V/cell.

Not storing packs at ~1/2 capacity (~3.7-2.8V/cell) for extended periods of time:
Much like how over-charging LiPo batteries beyond their full charge level increases the internal strain on the pack, the same is true to a lesser extent for lower cell voltages over a long period of time. It's generally accepted that storing LiPo batteries at ~1/2 capacity, which translates to ~3.7-3.8V/cell, is safe and is a happy medium for minimizing battery degradation over a long period. If you plan on not flying your batteries for more than a few days, it's a good idea to run what's often called a "storage charge program" on your balance charger to charge/discharge your battery to ~3.7-3.8V/cell. Then recharge your batteries back to full as soon as is practical before flying.

Draining a pack too far:
For normal use, permanent damage is caused to the battery if any of the cells drop below 3.0V/cell. Although as I mentioned previously, multirotors demand a lot from our batteries, so it's important that we try to keep the average cell voltage above ~3.4-3.6V during flight. This is because LiPo battery cell voltages drop off quite quickly below ~3.6V/cell, and so it's important to keep some margin to prevent any of the cell voltages from momentarily dipping below 3.0V before we can get the chance to land safely.


Take drone on a plane in Europe? I want to take my small (<250 grams) drone on a plane in Europe? Are there any rules regarding this? Should the drone go in carry-on luggage or in the hold?

I am not a legal expert by any means, so I just want to say that disclaimer.

As far as I am aware, you can check in the drone itself, but due to their volatile nature, most airlines will require you to carry LiPos in your carry-on luggage so you can react quickly in case the worst happens.

As always, check with your specific airline and the laws specific to your country of origin and your destination.


How long does a LiPo battery last and how do I know if it needs replacing? I have an old LiPo battery, how long is a LiPo battery usually supposed to last? How will one know if it needs to be replaced?

How long is a LiPo battery usually supposed to last?

Most LiPo batteries are not rated to last longer than 300 charge cycles. That is the battery fully draining and charging again. However, measuring a LiPo battery’s lifespan may not be practical, as batteries go through varying depths of discharge when they are used.

Many manufacturers have stated that their LiPo batteries will last 2 or 3 years. This is a somewhat realistic approximation for a scenario where a battery is regularly used and charged around 2 or 3 times a week.

  How will one know if it needs to be replaced?

After a LiPo battery goes past its lifespan, it can't hold as much charge anymore, so look for signs that it doesn't last as long as it used to on 'full charge'.


Unrecognised ESC motor connector I purchased an ESC and a Speed 400 motor about 17 years ago with the intention of building my first electric powered model plane. Life took its various turns though and my time for R/C modelling dried up soon afterwards. Now that I have 3 boys who are all starting to show interest in the area, I've started to find the time to look at it all again... yay!
Part of the reason I never got to build that electric plane originally though was that I had no means of connecting the motor to the plug included on the ESC. I know I could just cut the plug and replace it, but I've been trying to identify the type of plug without success for a while now.
Can anybody tell me what the type of the red plug in the image below is?

As an aside, I'm a bit mystified by the battery connector, since it has 16 guage wires onto the ESC, but then connected to much smaller guage wires with a JST plug. I don't have any specs on the ESC itself unfortunately, so don't know what the rated current is and consequently whether or not I should be concerned about those wires!

I agree, it looks like a Micro Deans plug. They're good for about 10amps. A red JST plug is good for about 5amps. A speed 400 is pretty inefficient over about 5amps.
Personally I'd junk both the ESC and motor and go brushless. You'll save weight, gain efficiency, be able to use a bigger prop and it won't wear out. And that ESC probably doesn't have a lipo-friendly low voltage cut-off.


What is this ring attached to the bottom of this rotor shaft? My motor came with a black ring attached to the bottom of the rotor. It spins along with the rotor, and it's not exactly a ring shape since it's open at one end - kind of like an omega symbol or like a stag beetle's horns. What is it called and what is it for?

That is a circlip (or C-clip) - it looks like it is used here to prevent the shaft from coming out of the bearing.
From the Wikipedia link above:

A circlip (a portmanteau of "circle" and "clip"), also known as a C-clip, Seeger ring, snap ring or Jesus clip, is a type of fastener or retaining ring consisting of a semi-flexible metal ring with open ends which can be snapped into place, into a machined groove on a dowel pin or other part to permit rotation but to prevent lateral movement. There are two basic types: internal and external, referring to whether they are fitted into a bore or over a shaft. Circlips are often used to secure pinned connections.


Is there a benefit to using multiple capacitors on FPV drones? From what I've heard, you need at least one capacitor on the ESC of a drone so that it can smooth out the voltage spikes to prevent electrical noise and improve the longevity of the ESC. If this is the case, wouldn't having more than one capacitor wired in parallel help further smooth out voltage spikes? Say on a 5'' drone, would it be worth the extra weight to have 3 capacitors instead of 1?

Capacitors come in various sizes and values, so one big capacitor could equal two smaller ones in value; I do not know for certain if this offers a weight saving, but can reduce PCB footprint size by being 'taller' (although, you can stack capacitors of the same footprint.)
A reason to have more than one would be to adjust the frequency response, as a capacitor's reactance is related to the frequency and the capacitance:
$$X_c=\frac{1}{2\pi fC}$$
where $X_c$ is the capacitor's reactance, $f$ is the frequency of the spike/noise and $C$ is the capacitor value.
To this end, you often see multiple capacitors for decoupling or filters; however, in an application where the aim is to decrease voltage sag it is less crucial. There are almost certainly more capacitors on the board, which may be in parallel to the larger capacitors (design dependent), but positioned close to the ICs and other parts so that each component gets the voltage it requires.


What process should I use to ensure my motors are spinning the correct direction when using Betaflight I heard that a lot of problems occur due to one or more motors spinning the wrong direction.  What process should I take to ensure that all my motors are spinning the correct direction if I'm using Betaflight?

Checking Direction

In Betaflight you can have your motors spinning either props out or props in. The default is props in (towards the body of the quad from the front and back). Be aware other flight control software such as FlightOne and Kiss have different defaults.

Default Direction

Reversed Direction

If you are running props out, make sure you flip the switch on the Betaflight configuration tab to adjust that, otherwise your first flight will be VERY short and very fast!

Note that this switch does not change the actual direction of the motors! It's just a way for you to tell betaflight which way they're actually spinning. To check that the displayed and actual directions match, do the following:

In Betaflight go to the motors tab, read the warnings, then plug in your battery and click the enable motors switch. Run up the motors one at a time from their slider and ensure they match the direction and position of the charts above.

If you don't have access to a computer, alternatively you can simply arm your quad without props on and check the direction that way. Make sure you don't raise the throttle though, or airmode might kick in and you'll have the motors wind up due to I term buildup from the PID controller. This isn't an issue from the motors tab, so choose that option preferentially if you can.

In both cases, you can either brush the flat of your finger lightly against the motor or put a piece of tape on the shaft before you run them up. Make note of any motors that are out of order or not spinning the direction you want.

Changing Direction

There are two ways you can fix the motor direction. One relies on a soldering iron or bullet connectors, the second relies on using software to change the direction.

Method One - Physically Change the Wires.

On the motors that are not spinning the correct direction simply desolder and switch pads on the ESC of any two of the motor wires. This will swap the direction of that motor.

Method Two - Betaflight and BLHeliSuite

If you already have your computer up, you can use BLHeliSuite to change the motor direction. The first thing you need to do is identify what type of ESCs you have. If you have BLHeli_S ESCs you'll need the Suite labeled 16.XX from the BLHeli Google Share. If you're using BLHeli 32 ESCs, download the 32.XX Suite.

Once you've downloaded the appropriate suite, make sure the Betaflight configurator is disconnected from your flight controller, extract the contents of the zip file, and run the executable.
Make sure you select the E (Cleanflight) interface from the interface dropdown list.

Select the correct COM port from the dropdown list (the same as Betaflight) and click connect.

Click the "Check" button on the right, then you'll see a confirmation of your ESCs and some summary information.

At the bottom of the screen, right-click on the ESC number that needs to be reversed, then go to the "Motor Direction" slider and change the direction.

Click "Write Setup".

Repeat for any other ESCs needed and then click "Disconnect".

Once you've finished, go back and repeat the check process once again until everything is correct! That's all there is to it!

Put the propellers on correct

Finally, when you go flying, ensure that you put your propellers on according to the direction of your motors. Most flip outs are caused not by the motor spinning in the wrong direction, but by a right propeller being mistakenly put on a left motor or vice-versa!

If you're new to the hobby, it might help to carry a sheet of paper with you with the directions printed on it, or color-code your motors and props with a marker so you can't go wrong.


Crossfire/Unify - Change Settings in TX and in OSD I have a Crossfire Nano RX and a Unify Pro32 Nano VTX.  I'm using the CRSF setting and wiring to allow the LUA script in the radio to change the settings in the VTX (power, band, channel, pitmode on/off).  I'd like to keep this functionality, but also be able to change VTX settings in the Betaflight OSD as well.  Is this possible?

Summary:

I'd like to keep the ability to configure the VTX via my radio
I'd like to add the ability to configure the VTX via Betaflight OSD

I believe the answer is no, you cannot use both. When you set the vtx up for lua in the radio, you change the communication protocol from SA to CRSF. You also remove the SA wire from the FC and move it to the Rx channel 1. So having just done this twice, it seems you get one or the other.


How can I build a drone similar to a DJI Mavic 2? I want to build a drone with the same functionality as a DJI's Mavic 2. Are there any books/videos/guides available? What would be involved?

I need a flying machine that:

has a good enough camera for short films
has at least 25 mins of flight time
is small and portable
has an object sensing system, so I don't wreck it :)
has a object tracking system to track people, cars, etc...

Its main purpose is "object tracking" for short films.
I know it will not be easy to build, but have the time and money to do it. I just need to know how.

Everything you requested is possible in a home-built unit (EXCEPT: object sensing and tracking.)

I'd recommend the painless360 youtube channel.  Lee has detailed build videos on just about every kind of RC model that flies as well as tutorials about radio gear, GPS, ESC, batteries, camera gear, etc.  They are excellent and you can follow along with the builds.  It makes building your first model a great chance of success.  His channel is amazing especially if you are new.  All the lingo, terminology, etc are explained there in some way in literally hundreds of videos.  This may sound like a shameless plug for his youtube channel but I've literally spent hundreds of hours watching his stuff since 2015 and learned so much in the process.  If you are new to the hobby, this is a must.

Painless 360 YouTube Channel

As for the sensing and tracking features, it would be very hard or impossible to build one that would do all those things effectively for less trouble and money the aforementioned Mavic series could.  Things like object sensing and tracking are still very proprietary software options and you're not going to make this yourself currently.  As stated in the previous answer: Just buy it from DJI if you really need those features.  Otherwise, build your own.  It's a blast.


How hot is too hot when it comes to multirotor motors? I hear this question asked all the time.  Are my motors getting too hot?  How hot is too hot for motors to get?  Anyone have a great way to answer this question, possibly with some temperatures?

I generally go by feel.  If I can pinch the motors with my fingers for at least a few seconds without feeling like they will burn me, I know the motors are not too hot.  I know a lot of people would like a more scientific answer than that.

Temperature is a killer of motors over time. If motors are exposed to prolonged heat, the magnets in the rotor lose their magnetic field strength over time and consequently reduce the lifespan of the motor.

Generally, a well-tuned drone should not have extremely hot motors after flying (with a few exceptions). It depends on the motor, but you should avoid raising the motor’s temperature past 170°F; any hotter, and you run the risk of damaging the rotor’s magnets and decreasing performance and longevity.

https://dronenodes.com/drone-motors-brushless-guide/

https://www.rcgroups.com/forums/showthread.php?1329288-Normal-brushless-motor-temperature-range