I have a Raspberry Pi 4B, 4GB version. When I try to run the following code it gives 0.3V output. I mean it works, on-0.3V, off-0V. But I need 3.3V output. I measured it with a voltmeter, as the interested device was not working getting only 0.3V from Pi.

import time
print ("LED on")
print ("LED off")
  • 1
    disconnect the interested device and measure again
    – jsotola
    Aug 4 at 14:42
  • What is the interested device?
    – CoderMike
    Aug 4 at 15:45
  • I am just using a tiny dc pump!
    – Aaron Crt
    Aug 4 at 16:34
  • 2
    your trying to power ANY pump directly from the GPIO? Not going to work.. What is the current required for this pump? GPIO pins can only supply 16mA if I rememeber correctly.
    – Chad G
    Aug 4 at 16:50
  • 1
    You could damage your Pi by connecting a dc pump directly!
    – CoderMike
    Aug 4 at 16:55

2 Answers 2


As others have pointed out in Comments (in response to your comment - which should be edited into your Question) the GPIO can only source a maximum of 16 mA and may be damaged.

You need a transistor or similar to control higher currents. There are hundreds of Answers on this site with recommended circuits (depending on the specifications of the pump).


GPIO have extremely limited current output; when overloaded, the voltage drops to near zero. This is a clear indication that you have "screwed up".

Use a transistor (or amplifier) to drive your "tiny dc pump" as shown in the schematic below:


simulate this circuit – Schematic created using CircuitLab

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