linked to my old question, Pro Mini 5v with Adafruit motor shield v1 power sharing problems

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I figured out and use one 7.2v battery (6 AA cells), and link it with RAW pin to Pro mini and join its 5v pin to motor shield 5v. It works but as I have a servo on this shield, 2 distance sensors so servo does not work well all the times. Stops or does not move as directed, shaking etc. I figured out that pro mini output 5v but only 150mAh which is not sufficient to run a servo which while sharing same 5v for motor shield. I need to know if I want to supply 5v 2000mAh from AA cells or 5v regulator, should I use these pins on motor shield (5v, Gnd, 9v)? I tried but it did not work. I did not find it anywhere on net.

  1. How can I use these pins shown in the picture.
  2. What is the min/max mAh value of current I can provide at these pins?
  3. If supplying input current at these pins, should I connect/disconnect power jumper?

    I am totally stuck. Need help. And here is the quick diagram how things are attached. All other pins are attached at shield connects to UNO when stack on it.

My robotic car diagram.

  • How well does it work in the following situation? : Jumper off; motor-power battery connected to Ext_Pwr; separate Arduino-power battery connected to pro-mini RAW (or 5V power supply connected to pro-mini Vcc); a ground pin on the shield wired to a ground pin on the pro-mini Aug 4, 2015 at 2:05
  • It worked but servo is not getting enough power so it gets lost many times and does not move at right time so left-right-center readings from u-sonic sensor not correct and car hits wall or stops in the middle.
    – Builder
    Aug 4, 2015 at 2:28
  • What are the rated voltages of the servos and the sensor? How do you know the servo is not getting enough power? To hold down electrical noise, power the sensor from pro-mini Vcc instead of from motor battery if sensor is rated at 5V. Minimizing electrical noise is one reason to use two separate power supplies. The motor driver and the pro-mini need to have a common ground but don't have to have common Vcc Aug 4, 2015 at 4:04

1 Answer 1


You can't, or at least you can't do it the way you want to. Each pin can give you a maximum of 40mA. You may try using more than one pin but that possibly wont work for you. I suggest you supply additional power from a separate source and control On/Off from Arduino. It would be like a relay. Or simply buy a relay to do this.

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