Turn Any Motor Into A Servo With RepRaps New Board

[Zach] just let us know about a new board that’s available from the RepRap project. It uses an AS5040 magnetic rotary encoder to measure the absolute position of the rotor of whatever motor you’re using. This is actually pretty damn exciting. Powerful servo motors are expensive, but with one of these, you can use whatever motor you can get your hands on. Big DC motors are cheap, but even used DC servo motors expensive. Best of all, the encoder is open source and you can score a kit version for a paltry $20. Now we can make that 8 horse power servo…

20 thoughts on “Turn Any Motor Into A Servo With RepRaps New Board

  1. Heh, those starter motors are bad-ass. Back in highschool, we had to make a mini go-kart type thing to navigate a short obstacle course for a competition. We mounted a starter motor on a piece of plywood, and hinged it to the frame so we could “clutch” the motor directly on the drive belt. The thing could zip around like crazy, and it only took a couple hours to put together.

    It was really hacky, but hey, look where I’m posting =-)

  2. I hate to be a naysayer but big DC motors are not cheap. especially ones in the 8hp range (a few hundred bucks at least.) an automotive starter motor would be cheap but they are easy to burn out if you run them for to long. also the Tesla roadster uses a 3 phase ac motor why do you think it’s named after Tesla? he hated DC motors (and Edison.) Tesla invented the AC induction motor which is still the most efficient form of electric motor. these things aside I think this is still awesome. it makes small to mid sized servos much more affordable. I might just buy one of these.

  3. This is new?
    I thought that using a separate encoder and motor was common practice my now?
    This is a good price break compared to commercial encoders, but I thought the general concept had been in use for quite a while.
    At any rate, open source + cheap kit still makes for a good post :)

  4. Treadmills have powerful DC motors. You can get used ones at yard sales for cheap (haven’t bought any but my parents have sold 2 old ones that the motors were starting to go bad on, though still worked, maybe would need new bearings or oil or something).

  5. steve: Yeah. 8+ hp motors are bloody expensive, but ever see how much an 8hp servo would cost? Are they even avilable?
    If you hooked the right AC controller board up, you should be able to use this to control AC motors (probably not worth it…)

  6. An actual servo versus a simple DC motor with a rotary encoder attached are two VERY different things.
    Don’t get me wrong, I think this is a neat and very useful device, and for many things we would use this for either one may work interchangeably to some degree. To say they are the same thing however, or that they can DO the same tasks is overstating things by more than a little bit.
    BTW, for cheap powerful DC motors, including treadmill motors, try http://www.surpluscenter.com, they always have some great random crap.

  7. Consider for a moment that your new powerful servo could also be used to run the steering of one of those powerwheels vehicles as well!

    Person weight translates wonderfully into payload weight on stuff like this.
    I’ve got my eye on a scooter like an older or disabled person would use right now for that very reason.

    My initial experiments with building my own wheeled rov included using a powerful gear motor for the steering of a two-seater barbie jeep. (painted primer grey of course) pink wasn’t gonna cut it.

    Mine wasn’t as refined as to use any feedback, I just built everything up to withstand jamming all the way towards one side or the other and kinda just winged it with the RC control to steer it, but it worked.

    Oddly what made me give up on it as a platform wasn’t the steering, but the lack of traction with those stupid plastic wheels, even when modified.

    I wanted my rov to go into the woods and such, which a differentially steered vehicle is much better suited for anyway.

    For on the street, or on grass a powerwheels vehicle would probably be ideal, and as stated would be a VERY inexpensive proposition.

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