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How many motor controlers do I need for two rc motors? — Parallax Forums

How many motor controlers do I need for two rc motors?

roughwireroughwire Posts: 78
edited 2007-08-29 20:44 in BASIC Stamp
·Ok, so apparently, just to swap my servos for rc car motors, I need a motor mind B? Do I need 2 or just one? It's really simple, I just want to swap the servos! But to run these motors, I would need to run a rc battery through the board right?·Is there another route?

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MIKE

Comments

  • D FaustD Faust Posts: 608
    edited 2007-08-27 17:08
    You don't necessarily need a motor mind B,l but if you want to use that motor controller I think you need two because they control one motor each. You could run the battery through the board or you could use a separate board (protoboard) and have separate supplies (ground hav eto be connected). Also you could wire in the extra battery to the boe's breadboard (like if you have a homework board for your boe-bot brains) Check out the servo connecting section of the boe manual for instructions on this.

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  • stephenwagnerstephenwagner Posts: 147
    edited 2007-08-27 17:59
    If you want to keep it simple, reliable, proven quality products, no frustration and lots of technical support, I would go with two (2) Parallax HB-25 Motor Controllers. Based on the picture you have attached, thoes RC batteries can supply over 20 Amps and thoes motors can draw more then 20 Amps. This much current will damage the moter mind B and or the BS2 carrier board shown. Keep in mind that there is no simple substitution or solution for what you are asking. The continuous rotation RC servos are complex positional closed loop control system where the control loop has been opened. There is not much dynamic range for speed control and they don't draw more then 1 Amp. The HB-25 is intended to be a powerful motor·controler with both speed and direction control. Your software will need to change.

    Another possible solution is to purchase sail winch servos from a big box hobby store. Sail winches have lots of power, however, they are slow. They are intended for RC sail boats.

    Are your interest in speed and or power and or position control and or school project and or just for fun?

    Stephen
  • Desy2820Desy2820 Posts: 138
    edited 2007-08-28 10:16
    Another option might be an ESC, an Electronic Speed Controller.·

    If memory serves, the ESC takes servo-style pulses from the RC receiver (which are servo pulses) and uses them to control the motors.· I'm not sure if they can drive two motors in different directions though, for tank-style steering.

    They vary wildly in quality and price, so start with a local hobby shop and look around.

    Just a thought.
  • roughwireroughwire Posts: 78
    edited 2007-08-28 17:17
    OK, so you thinks an ESC would be a better route? It's a school project so it would have to be fast, or else it wouldn't be cool... If you can picture it, try to imagine my Boe Bot, set up the same way strait out of the box, but instead of two parallax servos coming out of the frame, I just want to rc motors. It just sounds like there would be a super simple way of doing this...

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    MIKE
  • FranklinFranklin Posts: 4,747
    edited 2007-08-28 18:52
    Google for a dual channel H bridge. I think pololu has them.

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    - Stephen
  • stephenwagnerstephenwagner Posts: 147
    edited 2007-08-28 21:02
    Have you given any thought to how to mechanically connect the wheels to the new motors and mechanically connect the new motors to the BOE-BOT chassis?
    ·
    There is no simple solution to what you are asking.
    ·
    What would be really cool, cheep·and challenging is to purchase the Parallax wheel encoders·http://www.parallax.com/detail.asp?product_id=28107 and have the BOE-BOT perform controlled precision maneuvers on a hard surface. You will gets lots of support form Parallax·http://www.parallax.com/dl/docs/prod/datast/ApplyEncoder.pdf and learn some advanced math.· Now that’s an A+ project. It is all right there on the Parallax sight.
    ·
    Anybody can make a robot go fast. Try to make an articulated robot dray a straight line. Now that a challenge.

    Good Luck.

    Stephen
  • cyplesmacyplesma Posts: 76
    edited 2007-08-28 23:44
    how about a relay or optoisolator that the stamp can control to turn the motors on and off?

    made a pic



    oh, keep in mind you may need a couple of switching transistors to drive the 12vdc relays, depends on what kind of relays you can find. I'm sure you'll need pullup resistors though if you find relays that are controlled by 5vdc and can allow the right voltage to drive the motors.

    Post Edited (cyplesma) : 8/29/2007 1:23:25 AM GMT
    bmp
    bmp
    quickmotorcontrol.bmp
    653K
  • roughwireroughwire Posts: 78
    edited 2007-08-29 17:03
    this looks like the kind of motors I want. I'm not litterally going to put these in the boe frame, I just am trying to make it sound alittle more simple. This motor is by lynxmotion.
    Voltage = 7.2vdc
    RPM = 14,400
    Reduction = None
    Stall Torque = 36 oz-in (2.6 kg-cm)

    look!
    http://www.lynxmotion.com/Product.aspx?productID=183&CategoryID=72

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    MIKE
  • D FaustD Faust Posts: 608
    edited 2007-08-29 19:00
    You don't have to use relays if you want to use cyplesma' design. You sould replace the on/off realy with an optoisolator and make DPDT relay out of optoisolators see: http://forums.parallax.com/forums/default.aspx?f=15&m=209575
    Did you check the size of the motor to see if it fits? It looks pretty long and the leads have to come out the back too

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    Post Edited (D Faust) : 8/29/2007 8:47:13 PM GMT
  • cyplesmacyplesma Posts: 76
    edited 2007-08-29 20:31
    D Faust said...
    You don't have to use relays if you want to use cyplesma' design. You sould replace the on/off realy with an optoisolator and make DPDT relay out of optoisolators see: http://forums.parallax.com/forums/default.aspx?f=15&m=209575


    personally I would go with the optoisolators.
  • D FaustD Faust Posts: 608
    edited 2007-08-29 20:44
    Especially if you want to be stealthy! LOLtongue.gif

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