Robotics 2013-06-16

So close to having a walking robot that I can taste it… Today was equal parts assembly work and data sheet perusing.

The UPS man had dropped off a couple of 9V battery holders earlier in the week, one of which I mounted to the chassis after some soldering work. I also changed out the wiring to the DC plug I have such that the power for the micro-controller can be run to the breadboard as opposed to being directly tied to the battery (decoupling, FTW). Then I ran an assortment of wires and jumpers to power everything…

everything_mounted_and_powered

Perhaps after the next session the creation will rise and walk the earth…

I did a little digging in the micro-controller’s specs to figure out what my options are for driving all three leg pairs. It looks like pins PB2-PB4 double respectively as OC0A, OC1A, and OC1B. So, I’ll need to do some ribbon-cable magic to finish up today’s wiring exercise to get those pins linked up to the signal ports of all the servos. I figure I will use the two 16-bit timers for the side leg pairs and one of the 8-bit timers for the tilter leg pair.

Some maths have me reasonably convinced that I can make an 8-bit timer work for my purposes. A pre-scaler value of 1024 gets us to 8192 counter ticks per second. For a 50Hz signal, that means setting the roll-over for the counter (the “TOP” value) to 164. One tenth of that, ~16, is a 2ms wide pulse, and half that is ~8/1ms.

Right? We’ll find out soon…

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