1976 BMW 2002: Digital Gauges

My PCBs arrived yesterday from seeedstudio. First PCB I've ever designed, and it looks pretty good, I think. Soldering SMD components for the first time was a bit weird. The solder joints don't look super uniform, but they're not as awful as I sort of expected they'd be.

The board seems to work (the same as the breadboard setup I had, so I would hope it works). And it looks good doing it! A nice advantage of having a physical prototype that's in the final formfactor is that I can see what the whole thing looks like assembled. It's cool to finally see what the little displays look like behind the gauge faceplate. The pictures don't do it justice, it looks cool.

One thing I realized recently is that I'm probably going to want to drive the stepper motor with a smoother PWM sine wave signal, which means I need to switch some stuff in the circuit. So this first iteration is already outdated. I'm going to play with this design as-is for a while and see what I can do, then think about my next iteration once I have a much more solid idea of what works and what doesn't.

I completed a simple prototype of the speedometer/odometer circuit on a breadboard. Prototype PCBs are in production now, from SeeedStuido. The PCBs came to ~$35 for 10 boards, and the components are almost $100 / board. Most of that cost is LED displays, and the MAX7221 ICs.

I haven't written any code yet, except to test that I am able to drive the stepper motor and display drivers, via arduino libraries. Since this project is primarily about learning, I plan to write the firmware from scratch with the AVR-GCC toolchain.