Flight Controller Progress #2

by Octapoo

Friday, December 4, 2020 at 22:28:00 UTC

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Nothing soldered here yet, but I'm still making progress...

After drawing the first PCB, I wasn't liking the complexity of four ATmega328, so I reduced it to three. Now the chip which receives data from the RC transmitter's receiver simply ignores every other data packet and, when it should be receiving it, it generates the servo control pulses instead. This works fine because that receiver sends 129 data packets per second and I only need like 50, since I can send servo control pulses only 50 times a second anyway, so ignoring every other one is no big deal. This means I'm sending the servo control pulses about 64 times a second, but the servos seem to be OK with that.

The board is a reasonable size, it'll need only 5 jumper wires, and it has no traces that have to run between IC pins, as I exploited unused pins to take signals that would have had to go between pins to instead just connect to that pin, since the microcontroller can simply ignore that pin. So it was very easy to carve with my CNC machine. I think I can probably do traces between pins, but I need a smaller drill bit and have yet to order one and try it.

I'll probably start soldering and testing tomorrow or the day after.

There's still a lot of programming to do to make this do everything I wanted, but at this point I decided I've probably figured out most of what I'm going to want the hardware to do, and so I might as well make a first version of it at least. This will allow me to do some on-a-plane testing with it.

I also want to do some experiments with like putting it on a piece of flat square foam board with a couple of control surfaces and see how well it can control it while tied to a string and held in the path of a fan or some strong wind. I'd like to make a plane that requires little power to fly and I think a large flat wing surface like that might be the way to do it, but it would also be really unstable and impossible to fly manually, so I think having something like this to fly it might make it work.


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