NOTE: The following instructions show the construction into a PCB; to avoid confusion and be absolutely clear, this PCB is supplied by ourselves or is an option with the Hobby Components kit. If you want to use some breadboard to build your EDTracker, check out our other article.
Remember when soldering to follow some basic tips!
The soldering iron is hot. Well, duuh, that's obvious. You'd be amazed how many times you'll still burn yourself though. So don't say we didn't warn you.
Solder fumes are not the greatest thing to be snorting up, but unless you're doing this day-in day-out you should be ok. Still, it doesn't hurt to ventilate your room while working.
Don't apply too much heat for too long; the heat can damage tracks, melt plastic and ruin sensitive components. You're only soldering header pins here, so there should be little cause for concern, but if you're starting out on soldering it's worth remember that pumping 250 degrees centigrade into a tiny pin for several seconds isn't really a good way to go!
When working on the header pins, alternate around a bit - don't concentrate the heat in a single area by working progressively along the pins. You'll probably melt the plastic header strip. Jump around. Jump around. Jump up, jump up and get down.
Solder the button into the top of the board first. Pay attention to its orientation – the pins should align and push into place with minimal pressure; they do not need bending or splaying apart.
Note the bevelled corner of the PCB.
Place the header pins for the Arduino into the bottom of the board (two rows of 12 pins) - ensure the plastic part of the header pins is underneath the board.
Now flip the board over and solder the header pins into place; if they are a loose fit, make sure they don't drop down (this doesn't normally happen).
Flip the board back over to the top, drop your Pro Micro onto the pins (ensuring the USB connector is at the same end as the switch/bevel) and solder the two rows of header pins into place.
Flip to the top of the board and insert the header row pins for the MPU - it helps to put them short side facing up (ie. into the MPU board) with the long pins going through the PCB.
This is not critical to get right, but just saves you trimming the top pins afterwards.
Flip the board and solder the header pins into place in the PCB. Again, make sure they don't drop out slightly if they are loose.
Flip the board over to the top, then solder the 8 pins into place on the MPU. Ensure you keep the MPU board as flat as possible until the first pin is soldered - after which it will hold itself in place.