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New Electric Motor

  1. Jan 4, 2006 #1

    mrjeffy321

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    I just bought a new 300 watt, 24 volt DC electric motor which I plan to use in a couple projects I am working on.
    Here is a picture of it,
    http://www.electricscooterparts.com/ebaypics/COKEKMa.jpg

    The problem comes now that I want to turn the motor on and use it (something I guess I should have thought about in a bit more detail before hand).
    Do far, I have not been able to get it to work, I have hooked up a 30 volt DC power supply, but nothing happens.
    One would think that since this motor is suppose to output 300 watts, it would need at least that much power inputted (Power = volts*Amps). I seriously doubt that I was drawing 10 amps from my power supply while testing, as a matter of fact, its max is only 1 amp.

    So do you think this is the reason why it is not working? The only “documentation” I have on it I in the form of this picture,
    http://www.electricscooterparts.com/images/MOT-K24300hookup.jpg
    As you can see, it has a 5K Pot (whatever that means?) with Low, High, and Wiper setting. What exactly does this do and how would I use it?


    Also, I was looking for a better power supply option, rather than the AC/DC converter I tested it with. While browsing around Radio Shack, I saw these things,
    http://www.radioshack.com/product/index.jsp?productId=2102701&cp=&kw=transformers&parentPage=search
    http://www.radioshack.com/product/index.jsp?productId=2102703&cp=&kw=transformers&parentPage=search
    These transformers should be able to take the AC current from the wall and convert it down to about 25 VDC for use in the motor. But as you might be able to tell, I am not the most electrically savvy person around, and I don’t really trust myself with this type of stuff (especially with AC wall current) unless I get advice from others.
     
  2. jcsd
  3. Jan 4, 2006 #2

    Pengwuino

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    Well if your power supply is only made to output 1A and your motor is a 300W motor, its not going to work obviously ... or at least very slowely until you can give it more current.
     
  4. Jan 4, 2006 #3

    mrjeffy321

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    ya, I really didnt think things through when I bought it.
    So it looks like I need to come up with a much better power supply, or trade it in for a different motor.
     
  5. Jan 4, 2006 #4

    berkeman

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    I don't know what the 5k Ohm potentiometer note is about -- maybe you connect your own 5k Ohm pot there to control the motor speed, but I don't know how that would work. You need to get better documentation on the motor before you do much else. Check out the documentation for any scooters that use the motor, maybe? Especially if you can get a wiring diagram, and some idea of how big the batteries are.

    And definitely don't go messing with an AC line transformer trying to wire it up yourself. It's too easy to get hurt or start a fire. At the very least, you need to understand the UL regulations for how to handle AC line voltage at a power entry module (creepage, clearance, fusing, grouding, double-insulation if applicable, etc.) before you start wiring AC mains power up to your hobby projects.

    Can you physically spin the motor? Often that is a first step to understanding the wiring as you measure output voltages with the motor spinning.... Hook up a drill to the motor shaft with a shaft coupler and spin 'er up!
     
  6. Jan 4, 2006 #5

    Pengwuino

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    Sounds like the POT would just act like a throttle.... maybe?
     
  7. Jan 4, 2006 #6

    berkeman

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    Yeah, I just googled the motor part number from his brief info sheet, and got a couple hits. This one lists a 5k "thumb throttle" potentiometer to use with the "internal speed control module" in the motor:

    http://slo.craigslist.org/mcy/118538132.html
     
  8. Jan 4, 2006 #7

    Danger

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    As an interim step before buying a new power supply, you could probably use it with a standard automotive battery. It should run at about half of its normal rpm's. If not, then something else might be wrong with the set-up. Make sure, for instance, that the 2-pin kill switch connector isn't closed.
     
  9. Jan 4, 2006 #8

    mrjeffy321

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    Yes, the potentiometer is suppose to be used for speed control on the motor (for use in an electric scooter).

    I can spin the motor shaft by hand, but not to well, it is hard to hold on to. Using an electric drill to spin the motor is a good idea, but I cant tighen the drill around the shaft evenly and it wobbles a lot when I spin it.

    I do have a bunch of computer power supplies, which theoreitcally are up in the range of 300 watts. But I can only get about 125 watts, theortical max from a single output.
     
  10. Jan 5, 2006 #9

    Cliff_J

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    mrjeffy321 - the motor has some sort of speed control circuitry built into it, the 'throttle' pot is necessary for the circuitry to allow the motor to spin at all.

    It is a brushless design, meaning the circuitry needs to alternate the electromagnets to allow the motor to spin. Had it been a simple motor with brushes, it would automatically spin with power applied since the brushes on the commutator would automatically alternate the electromagnets based on position. But instead, here the circuitry needs to be activated first, then determine position, then energize the electromagnets.

    A potentiometer has 3 connections, at least the wiper is clear and low/high may just be references (or may need more too, documentation would help).

    http://www.markallen.com/teaching/ucsd/147a/lectures/lecture3/1.php
     
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