I'm a little bit late on posting this, had some computer issues last weekend. But I am back now. I finally wrote a simple program to run the Kartbot for some initial testing. The program will eventually evolve from this codebase, but at present, it's missing a lot, and is a rough draft to just get basic throttle functionality, not much else. Here's the code:
You can see that I've got provisions in there to make use of an LCD display. I also played around with the pin arrangement quite a bit to make sure I wasn't on the hardware SPI or I2C pins. Anyways, let's get to some pictures of the assembled setup.
Safety first! I didn't have a drill bit (or a drill) that could drill a hole big enough for the emergency kill switch. But I did have an axle washer from one of my old cars that was just the right size. So I welded it onto the frame.
Nice simple safety switch, easy for the driver to reach. I pretty much just use it as an on/off button the the electronics. It cuts power from the 12v regulator and shuts down everything. Even locks up the electrical brakes which have to be energized to be unlocked.
I needed some kind of case to put the electronics into. Wouldn't hurt if it was at least water resistant if not fully waterproof. This is what I came up with. Plastic case I had laying around my garage. It originally had some automotive electronics test equipment in it. Stuff I don't need and can't use anymore.
I guess I should mention the seat while I'm here, this is about the only picture I have of it, for now. I got it from a friend at work, it's from a "shift cart". It's a great seat, suddenly made the frame fit the driver properly, and it hugs your hips very tightly to keep you planted.
Did I mention the pedals? They're from a video game steering wheel and pedal assembly. I picked them up from someone on CraigsList for like $20. Each pedal has a potentiometer that gives a nice 0-5v reading into one of the ADC's. Works excellent as a throttle control. The module is simple zip tied to the frame for the time being.
This is how it's currently setup, the OSMC's are bolted through the case on each side. For the initial test run, I just ran the ribbon cables to the controller in a breadboard. In the left front corner of this case are the 5v and 12v voltage regulators. You can kind of see in the middle where the power harness comes up through the bottom of the case.
This is the underside of the case. I haven't run a holesaw up through the bottom to allow the fans to pull air in yet. You can see the cluster of ground terminals to the middle right of that picture, it's the yellow plastic. The DB9 connector hanging down at the top of this picture on the right side, that's the "signal" from the pedal cluster. Nice clean quick disconnect setup.
This was the maiden voyage, first test. I had taken the Kart to the Tacoma Robotics Society monthly meeting after having it ALMOST done. Pretty much just had to plug the ribbon cables into the correct spots on the breadboard, which I did there. Turns out the speed is seriously underwhelming. Much like you'd kind of expect from a wheelchair base. heh.
Next up, try out some braking, maybe try implementing the differential steering that many people have predicted won't work at all. And I definitely need to come up with a way to gear this thing up, which will probably simply involve moving the rear tires to a new rear axles, and doing chain drive off the motor controller gearbox outputs.