A number of weeks back, it occurred to me that as an adult with disposable income, I could buy a robot anytime I wanted to. So I did. Or rather, I bought a kit to build my own robot. I haven’t had as much time to play with as I’d like (the downside to being an adult with a job), but I’m hoping to take it out to Albuquerque Mini Maker Faire this weekend, so I’ve been experimenting with programs to show it off.
Here’s a video:
Cute, eh? That was just me making sure that the sensor “whiskers” work, but it’s kind of a convenient program because I don’t have to worry about it falling off the table. Right now, I know how to make it flash lights, move the wheels, and make noise with the little speaker on top, so either I should make a box for it to play in and teach it to do basic collision avoidance, or maybe work on a program where people can touch it and have it react, much like the one it’s running now. I’ve only got a couple of days to finish: Maker Faire is the 24th and 25th!
how do the wheels work? are they stepper-motors, motors with encoder feedback, or open-loop motors (no position knowledge/feedback)?
The wheels are attached to these servos. I honestly don’t know too much about them, since this is my first foray into robotics since I was a teenager, but I gather they’re the same as the ones Bandit was using for his line-following bot, so you might have played with them before. I assume they’re open loop; they don’t seem that smart, but maybe I’d be pleasantly surprised if I dug through the data sheet.
Those are rotation servos. They are closed loop, but the loop is closed at the servo. 0-50RPM. You will want to gear it back up a bit to run my walking linkage. Perhaps 2:1 to 3:1 pulleys (small one on the linkage axle, large one at the servo)
We could look at the PWM frequency. That freq. could be set on an Arduino, and they should be able to work directly from a standard PWM output pin.
I should look into a source of cheap(ish) continuous rotation servos, and perhaps design a mount to use them with the walking linkage.
If I ever get that thing injection molded…. It is looking like a realistic time of at least 20 hours to print a robot.
oh. here’s one for $5. I should look into putting together a walking linkage using these rotation servos instead of open-loop motor controllers.
http://www.robotshop.com/9g-continuous-rotation-micro-servo.html?utm_source=google&utm_medium=base&utm_campaign=jos
can those continuous rotation servos go backwards? Like would roughly 50% pwm make them stop, very short pulse goes 50RPM backwards, and long pulse going 50RPM forwards?
Yup, that’s how these ones work: http://www.parallax.com/Portals/0/Downloads/docs/prod/motors/900-00008-CRServo-v2.2.pdf