Microcontroller and Motor Sharing Power

Discussion in 'The Projects Forum' started by Teacup, Jul 15, 2013.

  1. Teacup

    Thread Starter New Member

    Apr 19, 2010
    Hello! I am doing a little bit of hobby robotics at home and unfortunately my electronics side is a little bit lacking. I would prefer to share the power supply between the micro-controller and the two DC motors and I know enough to know that in high demand situations the motors might draw enough to temporarily shut down the micro-controller.

    So I need to place a capacitor somewhere in the circuit. But my problem is that I don't know where, or of what value or with what additional circuitry I should place it in.

    I am using:
    -12V worth of AA's
    - An old Arduino Decimilia
    - 2 small motors that take 3V and have a stall current of 2.1A.

    I am trying to learn how to construct this circuit and why it would be constructed like that but I am having a hard time finding the referrence material. Would anyone be able to put me onto something with which i can figure out how to do it?

  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    Just a rhetorical question, but why do you want to share the power supply between the micros and motors? In this situation, it is better to have separate sources of power.
  3. Shagas

    Active Member

    May 13, 2013
    Use a 78L05 5 volt regulator for your micro .
    Put a large electrolytic of 1000-2200 uf across your batteries to prevent voltage drops.

    What are you using to controll your motors?
  4. wayneh


    Sep 9, 2010
    I think a large cap on the micro's side of the regulator would be more helpful than one on the battery side.
  5. tshuck

    Well-Known Member

    Oct 18, 2012
    Is 2.1 amps reasonable for a AA battery?

    You may want to look into another type of battery if not...

    Also, why do you need 12V for 3 V motors and an Arduino?
    Last edited: Jul 15, 2013
  6. tubeguy

    Well-Known Member

    Nov 3, 2012
    According to the specs of the Arduino, it needs 6vdc minimum, preferably 7vdc, so it appears to have an on-board regulator.
    What type of batteries are these? You might be able to power the motors and Arduino separately.
    Or, parallel the batteries to make a higher capacity 6-volt pack, with a few thousand uf's of caps across the pack.
    You could further isolate the MCU supply with a small value series resistor followed by a few 100 uf's of cap's plus maybe a small ceramic bypass.
    Last edited: Jul 15, 2013
  7. wayneh


    Sep 9, 2010
    There are a wide range of solutions. I think we're all guessing without more information from the OP about what the constraints are.

    Me? I'd consider making a 3V pack with all the batteries and using a small boost converter to roughly double the voltage to power the micro. If the motors draw the voltage of that pack too low, get more batteries. It's not safe to run those batteries at such a high current that the voltage drops that much.

    But again, we need to hear from the OP.