I have a project which has a 12 V DC motor controlled by a raspberry pi through a l293d.

The motor draws about 600-800mA from the power source while it is running, and > 1A (much greater) when it stalls.

Id like to detect the stall via gpio so the raspberry PI can stop it.

So I guess what I want is when the motor is drawing 1A or more I'd like to send a +3.3V signal to the GPIO.

I'm not exactly sure how to go about this, or the easiest way to "sense" the current.

Any help would be appreciated.

  • 2
    Hello and welcome. Personally I'd recommend to ask this at electrical engineering SE as this is really not Pi specific.
    – Ghanima
    Apr 1, 2015 at 21:40
  • Yes, please ask this at EE.
    – Janka
    Nov 10, 2016 at 13:52

2 Answers 2


Generally you would use a low value resistor - a few ohms - & amplify the voltage across that. The resistor goes in series with the motor - in the negative lead is usually easier - it reduces power to the motor, which is why it wants to be tiny.


Do some search on current sensors and see if you find a suitable (preferably for raspberry pi or arduino).

I haven't done this before, but i think if you poll such a sensor at a reasonable rate and check the current it might work.

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