0

I encounter a power behavior for my Raspberry Pi 4B that I struggle to explain. I try to power a (geared) DC motor using the 5V pin. DC motor is rated for 3-12V (preferred 6-8V) and is claimed to draw <150mA. From what I have read (Raspberry Pi Power Limitations), the 5V pin is directly linked to the power supply (here an official Raspberry Pi power supply). I would therefore expect a steady 5V.

When connecting the motor to the 5V / GND pins (through a breadboard), the voltage measured on the motor drops to ~3.9V and the motor starts. I tried to boost the motor using a MT3608 DC-DC boost, knowing that even targeting 10V on the motor and assuming a max current drawn of 200mA, I would be far from the theoretical minimum of ~550mA (How many current can I put in the 5V pin?). To make it work, I need to boost the output voltage quite high (~9V) to erratically get it started (I blame the breadboard bad connections for this). Then the output voltage of the MT3608 drops down to ~4.5V and its input voltage (which should be 5V) drops down to ~3.8V. The motor is still more sluggish than when directly connected to a simple 9V battery.

What did I miss with the Raspberry 5V pin / power supply, and how can I properly power the DC motor? Is it related to the intrinsic torque/current/voltage property of the DC motors?

4
  • 2
    Why not power the motor with an external power supply? You have not mentioned your motor driver. Some can drop a volt or more between input and output so 5V to 3.9V is not that unlikely. I do not see this as a Pi specific question.
    – joan
    Commented Jul 4, 2022 at 19:45
  • For the convenience of using only one power supply/plug if it's possible (the place where I intend to use it has only one wall socket, and the math seems to add up for powering it with the Pi). Regarding the driver, I plan to use a DRV8833, but for debug purpose I tried first ditectly on the 5V pin. If the 5V comes directly from the USB 5V, then I guess my issue is with the power supply.
    – adelille
    Commented Jul 4, 2022 at 20:48
  • 2
    You can use a power strip to get more plugs. In addition, it is a very bad idea to power a motor directly from a pi, because it can destroy your pi. I learned this several years ago when I was into robotics.
    – NomadMaker
    Commented Jul 4, 2022 at 21:42
  • A power supply the Raspberry Pi is NOT!
    – Gil
    Commented Jul 5, 2022 at 0:46

0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.