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DC Motor

LorraineLorraine Posts: 4
edited 2007-06-09 11:53 in BASIC Stamp
I am working on a senior project and I am trying to energize a 9VDC motor (which only needs about 3VDC for what I am doing with it) and I cannot get it to work.· I have tried driving a relay to power the motor and it will not work.· Does anyone have any ideas????· Thanks

Comments

  • D FaustD Faust Posts: 608
    edited 2007-06-08 00:44
    Will the relay actually "click" Are you trying to activate the relay directly from a stamp pin becaus that won't work. Stamp pins can't supply enough current so the pin needs to drive a transistor which drives the relay. There is a schematic on the forums somewhere, but I couldn't find it. If this is not your problem then check over your wiring to make sure that the motor is getting enough voltage and is connected to ground and a voltage. Hope I helped.

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    D Faust
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2007-06-08 01:42
    http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv6.pdf


    ·http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv23.pdf

    Post Edited (PJ Allen) : 6/8/2007 1:47:24 AM GMT
  • WhitWhit Posts: 4,191
    edited 2007-06-08 03:02
    Man, those Nuts and Volts articles are good.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • LorraineLorraine Posts: 4
    edited 2007-06-08 11:52
    Yes, I have tried using a 2N3904 transistor as a switch to control a relay.· I think I may be connecting the relay wrong.· I have a DPDT relay with 10 pins---data sheet attached.· I appreciate all your input.·

    http://www.nteinc.com/relay_web/pdf/R74.pdf
    ·
  • stamptrolstamptrol Posts: 1,731
    edited 2007-06-08 12:10
    On the relay:
    pin 1 to + of coil/motor supply
    pin 2 to collector of transistor
    pin 3 to + of coil/motor supply
    pin 4 to motor lead #1

    emitter of transistor to - of coil/motor supply
    motor lead #2 to - of coil/motor supply

    Connect all supply negatives together (stamp supply, coil/motor supply)

    Base of transistor through 470 to 1K ohm resistor to stamp pin

    Cheers,

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    Tom Sisk

    http://www.siskconsult.com
    ·
  • D FaustD Faust Posts: 608
    edited 2007-06-08 19:13
    Does the relay "click"?· If mit doesn't then you aren't triggering the relay and your problem is that.· If it does I would try what stamptrol said.

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    D Faust
  • LorraineLorraine Posts: 4
    edited 2007-06-08 19:37
    No, the relay does not click.· I am not at home right now, but I will try hooking the relay up as stated above.· I have to hook it up so that the arm on the motor will turn clockwise and counter clockwise.· This whole project is to lock and unlock a door.·

    I appreciate everyones input.
    ·
  • LorraineLorraine Posts: 4
    edited 2007-06-08 23:23
    Ok--Here is the update--the relay is working but it like shorts everything out when I plug it up to the motor. When I put an LED on the output of the relay it works. Does anyone have any ideas on what to do with this problem?

    Thanks.
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2007-06-09 06:36
    Lorraine -

    You are probably missing the back EMF protection diode in the relay coil circuit. Here is a diagram which should help:
    http://www.hobbyprojects.com/the_diode/diode_protection_circuits.html

    Regards,

    Bruce Bates

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  • stamptrolstamptrol Posts: 1,731
    edited 2007-06-09 11:53
    Also, what are you using for a power supply? Sounds like you're drawing too much current and the voltage is collapsing.

    At the least, the motor supply should not be fed off the stamp internal regulator.

    Cheers,

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    Tom Sisk

    http://www.siskconsult.com
    ·
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