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K-9’s Drive System

December 12, 2009

Work is insane (crunch time for a new product launch is like that). Kathy’s 7 months pregnant and becoming less mobile by the day. The leaves need raking, Christmas decorations have to be put up, the kids want to play, next year’s household budget needs to be set…

So, let’s talk about something fun, like K-9. With physical construction largely complete, he basically sits under the baby grand piano in our living room, peeking out. Progress has stalled due to my own lack of knowledge. Specifically, I wasn’t sure what kind of motors I would need to make him move. Asking around, I received recommendations for wheel chair and windshield washer motors. But they are heavy (7-10 lbs each) and expensive ($150 per). At the other end of the spectrum, the guys at the local hobby shop swore by these little $10 motors that didn’t look like they could lift much more than a toothpick. To make matters more challenging, the various web sites and stores I visited didn’t use comparable specs to describe their products. “Great for large robots” isn’t helpful. What’s large?

Eventually, I stumbled on the RD02 12-Volt Drive Kit from Devantech at the RobotShop. It looked about right, including motors, 4 inch wheels, motor controller and mounting brackets. The description was clear – “Perfect for robot platforms from 5 to 10Kg”. (To Americans, like me, that’s 11-22 pounds and plenty powerful for my needs.) A little casting about on the internet showed it would work with the Arduino I already had. It looked right. But at $230, it wasn’t cheap and I didn’t want to get stuck with the wrong thing.

Then two weeks ago, during a particularly boring monthly operations call at work, I was Sametime-ing (instant messaging) with our global sales leader. He happens to be a big radio controlled car enthusiast and knows an awful lot about just this topic. I sent him to this blog, we discussed a couple of options and he agreed that the RD02 would be the best path forward. The simplicity of having all the components pre-configured and pre-tested would be worth any savings I’d get from buying individual components or visiting the local junk yard. With his blessing, I placed the order and it should arrive this week. I can’t wait!

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