Very cool! I’m always glad to hear about people making balancing bots, especially since BalBots HQ caught fire and they stopped selling the kits.
I agree that a serial servo controller will not respond quickly enough to balance a balancing bot, but you can certainly use the GWS servos you have now as straight DC gearmotors. You just need to rip out the electronics board (you could actually leave the POT, but do remove that white clip) and connect the DC motor leads to one set of the motor carrier board’s output terminals. As for whether they will cut it for your balancing bot I can’t say (I haven’t built my own balancing bot you see), but you might want to start with them for now since you have them. I would tend towards bigger, beefier DC gearhead motors. I don’t have any to recommend offhand, but more torque AND speed can’t hurt, and a bit more mass down low could be a big help in controlling the inverted pendulum system.
As to why the carrier board has the control pins brought out and labeled, and in the mini-header, that board is sold separately by Pololu as a standalone Dual High-Current Motor Driver Carrier, which you can use with your own microcontroller connected to those interface pins. It’s also bundled as part of the super-cool TReX Dual Motor Controller.
And thanks for the praise, I’m actually a fan of Pololu’s sparse but complete documentation style (there’s a little debate going on about it here). You do have to do more figuring for yourself, but I find that it makes it easier to find the information you want without having to dig around for it. For example, most electronics manufacturers wouldn’t dream of publishing complete schematics of their products. It can cause problems if something is counterintuitive and/or you miss it in the manual (I definitely spent about a day staring at my first Pololu motor controller for want of a pull-up resistor) but at the same time the manuals are short and well-written enough that it’s not a huge hassle to read through it again. And when all else fails, you go to the forums!
-Adam
P.S. The Electromechanical Systems class here at the University of Michigan is building full-size human-carrying balancing vehicles from scratch this semester, how cool is that!?! The Engineering Design Expo they’re supposed to be presenting them at is tomorrow in Lansing, Michigan. I haven’t checked up on the class recently, but I’m really hoping they got something to work! I talked to one student in the class about three months ago who said there was no way any of the teams would get anything working, and another student a couple of weeks ago who said they’d be totally ready, so here’s hoping!