So, it's been a while since our last blog post, but that doesn't mean we've not been working away on our robot, far from it.
We've done a lot of work on the body, including paint, decals and mounts for lighting. There's still quite a bit of work left to do in this area, but it's more than good enough for us to move on to other areas of the robot.
Foolishly I managed to blow up the Pi we were going to use (A Pi 3 A+), absolutely 100% my fault and I ensured I was suitable chastised for the crime. But I don't have a direct replacement in my collection of Pi, so I have opted for a Pi 3B+. As it happens, I think the extra ram could make a bit of a difference, so it's turned out better in the end. As the mount for the Pi is an integral part of the chassis, I had to take the robot apart for the 43rd time and reassemble, we all know this wont be the last time. In fact, all of the acrylic sheet is going to be replaced at some point, so the entire robot is coming apart again at least once or twice.
One area that we identified as a possible issue was the front wheels, they are quite vulnerable, especially as we've gone with larger wheels for 2020. So We're experimenting with a front bumper with a small wrap-around to give a little protection for the front wheels. We are using the Pololu micrometal gear motors and we're already in the habit of destroying the little gearboxes, so thought it best to not increase the risk even further.
Please excuse the wiring, it wont look like this in the future.
It wouldn't be a Pi Wars robot without flashy lights, right?
The only thing we can think of that's better than flashy lights at being flashy lights, is coloured flashy lights. So We ordered some 10mm RGB LEDs and set about building a light bar to sit atop our robot. We considered a few ways that we could control the four LEDs, with using the GPIO pins on the Pi not even considered as an option as this would hog far too many of the GPIO pins. One option was to use an off the shelf LED driver board, but I really felt it was better for us if I was to make something myself.
So the option we decided to go with was a 16-Channel I/O Expander, the MCP23017 in fact. This works via I2C, so no tying up GPIO pins and it has more than enough pins to drive the four RGB LEDs.
I wanted the light bar itself to be as compact as possible, and the size we went with in the end meant that it was quite a squeeze in there (see below). There's a little hot melt glue in there, just to keep everything in place and prevent the connections from moving and shorting with each other, it's not pretty but with some silicone potting it will look a bit better.
So, whilst I'd like for it to have been a bit tidier, I am pleased to report that it works really well and besides you wont see the underneath when it's mounted anyway.
Each colour of each LED can be controlled independently, so any LED can be any colour at any time and whilst this is hardly ground breaking, it still looks pretty.
On to the next task now.