03/05/2017 at 16:03 •
I started de-soldering connections, more or less working my way backwards until something worked like it was supposed to. Except that never happened. I broke down and bought another batch of components which should arrive soonish. From the testing I've done the circuit should actually work, which leads me to believe that the micro is fried. Unfortunately, it'll be a huge pain to swap it out since basically everything is built up around it. I think I'll replace it with a socketed ATtiny85 8-pin DIP, since I actually have some now. I've learned my lesson - I'll be using IC sockets for everything from this day forward. I've been slowly getting the hang of DipTrace and I may just send out a board to get fabricated like a normal person.. as cool as the deadbug air wiring looked I think I need to take a different approach.
I'll update this log once parts show up and I figure out what I'm doing with my life.
EDIT: DERP the schematic I uploaded is wrong. I criss-crossed the coils on the two relays. The actual hardware I have here is wired correctly, but the schematic is wrong. I'll fix it and upload a new one shortly.
03/04/2017 at 16:12 •
I took some time this weekend to continue assembling this thing.
At this point there wasn't much left for me to connect, so I prepped the batteries. A quick test showed that they weren't exactly balanced and I figured it would be bad to just... plug them in like this.
So I shorted them together through a power resistor. Now kiss! Also I put them in a frying pan in case I suddenly found myself with a smoldering pile of plastic and lithium.
And now the moment we've all been waiting for!
I plugged in the button and... it doesn't work. As soon as the microcontroller powers up it seems like all the pins go HIGH - the LED's go to max brightness, the relays jump back into "charge mode", and the one pulsating LED in the button never fully dims. I need to figure out if I fried the microcontroller or if there's something else at work here... This is what I get for jumping straight into assembly without testing the subsystems first.
08/29/2015 at 19:58 •
As I populated the board I had to make a few tweaks to the layout.
Look at all those potential shorts! If only I knew what I was doing... The LiPos I bought have built in protection circuits that should protect against short circuits but I can't shake the feeling of impending catastrophic failure and lithium polymer battery fire. I'll just try extra hard not to drop it so it doesn't explode. Actually, that's exactly what happened in the opening scene of Guardians of the Galaxy so I'll consider it a feature.
08/29/2015 at 19:31 •
I decided to put the charging circuitry on first. The charge controller I chose was an SOT-23 form factor, which is pretty tiny. I bought 4 of them fully expecting to destroy a few or sneeze and lose one forever. Turns out one was enough so now I have 3 extra to.. you know, charge stuff I guess.
I painted one side of the board white because I wanted to.
I plugged in one of the batteries and soldered up the wireless power modules to make sure everything worked as intended. It didn't explode and the LED came on when it was done, so I guess it works.
I went ahead and charged the other battery too, so hopefully they stay at least kind of balanced for when I plug them both in together. Unplugging JST connectors sucks.
08/29/2015 at 19:08 •
After selecting components I decided to tackle board layout. I will be using a small piece of perfboard. I sketched up a wiring schematic or three but quickly discovered that this strategy would not work well for laying out components on the board. I downloaded Eagle and taught myself just barely enough to generate a compact board layout which would help me figure out where components should go and which side of the board to put them. I couldn't quite find all of the right component footprints and the PCB traces are just general routing guidelines. I planned on deadbugging and air wiring some of the components anyway. This is one of my nearly final iterations.