Shop OBEX P1 Docs P2 Docs Learn Events
what circuitry will drive two dc gear motors? — Parallax Forums

what circuitry will drive two dc gear motors?

jaspittmanjaspittman Posts: 22
edited 2007-07-30 18:24 in BASIC Stamp
first let me say this is a first class forum. i am new to electronics and i need to control two dc gear motors.the motors need 500 mA each, both motors will be linked and are bi-directional. i do not need independent control over just one motor. i don't need pwm or brakeing ether. what is the cheapest way to do this with a bs2 and a 12V battery. thanks.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-07-29 00:33
    By linked, do you mean that they're wired in parallel? By bidirectional, do you mean that you need to reverse the direction of the motors as well as turn them on and off?

    Assuming that you do need to reverse the motor's electrical polarity (to reverse them), the easiest (and fairly cheap) way to do this is to buy a DPDT relay rated for 12V or more and at least 1A for current (better to double this). You'll need a switching transistor to activate the relay from the Stamp (see the "What's a Microcontroller?" tutorial for an example of this). To turn the motor on and off, you can use a power transistor with at least a 1A rating like the IRF510.

    A DPDT relay that RadioShack carries is www.radioshack.com/product/index.jsp?productId=2062483&cp=2032058.2032230.2032277&parentPage=family
    The IRF510 is also available from RadioShack: www.radioshack.com/product/index.jsp?productId=2062618&cp=2032058.2032230.2032279&parentPage=family.

    You'll also need some 1N4001/2/3/4 diodes to protect the transistor from the motor when it's switched off. The tutorial discusses this.
  • jaspittmanjaspittman Posts: 22
    edited 2007-07-29 00:41
    sorry by linked i mean they both move at the same time in the same direction. bi directional means forward and reverse.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-07-29 00:48
    The tutorial that shows how to hook up a motor or relay to a Stamp is "Industrial Control" page 86 (download from www.parallax.com/dl/docs/books/edu/ic.pdf).

    So, the DPDT relay will reverse the motor direction based on whether a Stamp pin is HIGH or LOW. The motor would be turned on by another Stamp pin.

    Here's an example of how the relay is used: [url=http:// http://www.electronicsinschools.org/page.php?m=3&ps=2&p=34] http://www.electronicsinschools.org/page.php?m=3&ps=2&p=34[/url].

    The two IRF510 transistors would be used to:
    1) turn on the DPDT relay as shown in the Industrial Control tutorial.
    2) turn on the power to the motor. If you look at the example above, the IR510 would be connected between the relay and the negative terminal of the 12V battery as shown in the Industrial Control tutorial.

    Post Edited (Mike Green) : 7/29/2007 12:57:01 AM GMT
  • D FaustD Faust Posts: 608
    edited 2007-07-29 12:21
    I think that the IRF510 would not be fully on at the 5V that the stamp can provide (9V I think).· Might this cause a problem for turning on the relay?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    D Faust
  • Mike GreenMike Green Posts: 23,101
    edited 2007-07-29 15:03
    You're correct, the IRF510 wouldn't be fully on with the logic drive of the Stamp, but, for driving a relay from a 12V supply, that shouldn't matter. If you look at the datasheet, it'll handle a load of 0.3A with a gate voltage of 4.5V. For switching on the motors, that would be a problem. A better MOSFET would be an IRL510 which can drive the motors with a logic level input.
  • D FaustD Faust Posts: 608
    edited 2007-07-30 18:24
    Thanks for pointing that out

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    D Faust
Sign In or Register to comment.