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This won't work will it....

Discussion in 'General Electronics Discussion' started by Choops94, May 20, 2015.

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  1. Choops94

    Choops94

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    0
    Apr 25, 2015
    Basically I have four GR02 Planetary gear motors (http://www.gimsonrobotics.com/GR02-12V_18V_planetary_electric_gearmotor.html) which I am hoping to power with two Turnigy LiPo batteries. (http://www.hobbyking.com/hobbyking/store/__9183__Turnigy_5000mAh_3S_25C_Lipo_Pack.html)

    I am connecting the batteries and motors to two Adafruit motor shields (https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino/overview) to hopefully work in conjunction with an Arduino Uno. I am, however, just noticing on the specs of motors and motor shields that the current values do not match well. Will it be possible for me to run these motors off this shield or will I need a higher current motor shield?
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Those motors require way too much current... so no, you can't use those unless you will be operating those motors with no load.
    You 'may' be able to piggyback on the motor shield and install or add-on mosfets that can handle the current. You will most likely need to build/buy a new driver though.
     
  3. Choops94

    Choops94

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    Apr 25, 2015
    That is what I was afraid of :( Thank you for the reply. If i was to construct my own motor shield what components of the motor shield would I need to change in order to up the current?
     
  4. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Start with the motor and work backwards.
    You need a Power Transistor or Mosfet that can handle 15 or more Amps.
    If you want your motors to travel in both directions, you will need 4 of them to make an H-Bridge. (This design will allow for variable speed control.

    If you simply want forward and back, and don't care about speed control, you could also use 2 Single-Pole Double-Throw Relays.

    From here, you can patch those to the controller, or you can look into additional parts to build your own shield from scratch.

    * Tip : You may be able to use the output to the motor to control your Relays or your Power Transistors.
     
  5. Choops94

    Choops94

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    Apr 25, 2015
    I see, thank you so much for your help, I'll get started right away!
     
  6. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Best of luck. You are welcome to share any ideas you have before you make any product purchases.
    One note for you those as well. The 'Stall Current' on those motors is incredibly high. I would suggest putting a fuse or something in-line with the motor in case it stalls you won't burn the motor up or the Power Transistor/Relay you plan to use.
     
  7. BGB

    BGB

    154
    11
    Nov 30, 2014
    I actually have the same basic motors in the linked page (albeit without the gearboxes), but even trying to spin up the motors (under no load) it likely do blow out the motor shield (they typically pull in excess of 4 amps when spinning up, and only really drop to around 1.5A-2A after they have fully spun up).

    those motors can actually take a fair bit of current before they heat up.
    they start getting warm when you run 20 or 30 amps through them, but run nice and cool at around 10 amps.

    for their size, they also have a fair bit of torque, as in many cases their torque is more limited by the power-supply than by the motors (they can actually be pretty scary powerful if run off lead-acid batteries). they are similar to the motors used in Power Wheels, and are a fair bit more powerful than those used in a lot of cordless power tools.
     
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