How to wire for AC mains voltage relay, when printer board is connected to AC-charging laptop computer? I know this will be a really obvious question to some people, but I have bricked about 3 boards doing this so I want to be certain before I brick a fourth. I don't have a lot of experience working with AC voltage, especially crimping / hacking it like what's going on here. Trust me it was my last resort to ask this.

Basically, as a chamber heater I'm using some 120V heat lamps (here in the U.S.). The problem seems to be that when I connect my laptop to the board (if the laptop is plugged in, which it has to be for long-term serial control), sometimes I:


Hear an electric shock sound -- the board is fried
Don't hear an electric shock sound -- the board is fried, though


What I interpret from this is that I'm stupidly wiring the 120V heat lamps incorrectly relative to my 3D printer board, such that when I connect it to my charging laptop via USB, the AC voltages are out of phase, causing my board to be fried. Alternatively, it's the 12V/24V power supply that's wired wrong relative to everything else, which also needs to be wired to the same polarity.


I was on the understanding that when crimping a three-wire male electrical cord:


White = Neutral
Black = Hot (or Load)
Green = Ground


... reinforced on the left side of the below image as well: 



So, I know that much already. The question is, when I connect this AC outlet to a relay like this, I got NO, COM, NC on one side and IN, DC+, DC- on the other. Which wire goes to COM, and which goes to D-? The board uses COM to denote the voltage that is switched 'on' by the relay, and D- to denote whatever the shared ground is among, the 3D printer, heat lamp, printer board, etc... (For more info, see link to relay)


This 5V relay says it supports AC loads being managed by an arduino / 3D printer, so I was under the impression that I could connect the white wire to its D- pin (which also should receive the "GND" for my 3D printer board) and the black wire to its COM pin. However, what do I do about the green wire? Nothing? Also, was it wrong for me to assume it would support this function when the Arduino is connected to a charging laptop via USB?

Basically, I just need to be sure that my laptop (3-prong), power supply (3-prong), heat lamps (2 or 3 prong) and relay (only 2-prong) all have matching polarities and don't cause an electric shock or fry my board. But I am getting really conflicting results and frying a lot of boards, probably by overthinking this.
In effect, the ground (from mains) does not need to be connected to the relay, the relay interrupts the "hot" or "neutral" (preferably the "hot", but that is not possible for all plugs, e.g. some European plugs can be inserted 180&deg; turned into the sockets). You connect one of the interrupted wires to the COM, the other interrupted wire (that goes to the lamps) to the NO (or the NC, depending on safety, the logic and/or preference). The ground wire from the mains power socket is not necessary at all (some lamp amratures require this to be connected though). See a schematic below, it uses an Arduino Uno, but you can think of it being the printer board. Note to never connect the ground from mains to the printer board directly!



Image based on source: osoyoo.com

The logic (low voltage side of the relay) needs to be wired as follows:


DC+ is the voltage power supply of the relay module, this is frequently +5&nbsp;V, but some modules use +3.3&nbsp;V (sometimes there is a jumper cap to select the voltage)
DC- is the ground from the printer board
IN is the trigger that needs to be connected to the port on the printer board that electronically switches the relay