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Thread: Bad GM20????

  1. #1
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    Default Bad GM20????

    I'm helping a friend build a driver board for a GM20 but it appears to be dead. I've put 5-12V@1A across pins 1 and 2 and get no actuation. However, I'm reading a coil impedance of 49 ohms. Any suggestions?
    Thanks!
    Adam

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    [QUOTE=300EVIL;124626]I'm helping a friend build a driver board for a GM20 but it appears to be dead. I've put 5-12V@1A across pins 1 and 2 and get no actuation. However, I'm reading a coil impedance of 49 ohms. Any suggestions?
    Thanks!
    Adam[/\\


    Is it wired green to black and driven red to yellow? For most of them that would be 49 ohms.

    When GM20s dont move, you can often make up a little jig to recenter the torsion bar and recover motion.

    Spex: http://www.camtech.com/products/Spec...PenMotors.html

    http://www.camtech.com/products/Spec..._736-49506.pdf

    Directions to getting Jiggy with it sent in a pm. (why did I just think of Will Smith???)


    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  3. #3
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    300evil, did you get the gm-20 to work? Alot of times it's difficult to tell if it's actuating unless you have something on the shaft. If you don't have a flag to mount to the shaft, just put a piece of tape on it.

    Don't forget to add a reverse polarity diode in parallel with the gm-20 to handle the back EMF. And 1N400x will do. Also, if you're going to use this for a shutter, you should add a capacitor in parallel, this will severely reduce bounce.

    At 5V it's only pulling 100mA so a 1A supply is plenty big. Also, at 5V, it's not moving much, only a couple degrees. In my projector, with a 2-1/4 inch flag, it's just enough to get the flag out of the beam path.

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