Yesterday I finished off most of the circuit boards for my new robot. I had to harvest some components from existing old circuit boards, notably the modular connectors I am using on the bumpers. The rest of the components were a mixture of new and old from various sources.
To finish off the main board I needed to find some resistors to use in a voltage divider. I am using one of the analogue pins to measure the voltage of the battery so that the robot can prevent damage to the cells in the event that the battery is used up.
After spending an hour or so sorting through my collection of SMD resistors I found that 22k and 3.9k gave a maximum voltage of just under 3.3v, assuming a hypothetical maximum charge of 21v. I’ve measured 20v on the battery packs so calculating for 21v adds a margin of error. I’ll measure the voltage on a battery pack when it indicates flat and use that as my cutoff point for the motors.
I also finished the sensor breakout board and the bump module boards, though I still need to add the actual bumpers. Stupidly I threw out hundreds of keyboard switches, long ago, so now I need to harvest them from existing hardware.
The bumper boards came out better than expected. There was one broken trace that needed bridging with a length of component lead, but other than that I managed to get enough solder in all the right places, even with the bad exposure. I’ve only installed one LED per bumper board but maybe I’ll add another, since I made the space. I think that would look cool.
Once the soldering was all done, I did what you can see in the picture and sprayed the boards with lacquer. They are still drying at the moment.
The next step is to find a Raspberry PI Pico to add to the main board and then begin mounting the boards to the robot. I’m not 100% sure how it will turn out so we’ll see. I still have no solution to the 5v problem and don’t have a sonar module that is compatible. Things are a little tight for cash so I can’t just go ordering stuff willy nilly
The sonar deck still needs to be constructed. That needs a tiny bit of sanding and then, okay it needs all the work done on it. Maybe this evening.