I've got a setup where I power RPi, 3G dongle from one power source (USB Hub powered from 5V 2A) and a DC Motor HAT and DC Motors (2 small car mirror motors) from a 12V 2A supply. I checked the motors and they work just fine with the 5V supply (although a bit slower but speed is not a priority, I'd even say that if they run slower I'll have more precise control). I was wondering if the connection scheme below is safe.


If there's too little power I suppose I can switch to more Amps. The purpose of doing that is to get rid of the USB Hub as I'm attempting to miniaturise the solution. Thanks for any advice.

  • Yeah that's defiantly too low power, if it works now, you will notice problems when you start loading the Pi cpu up wit code and will see it power off at random, I recommend that you place the do motor hat and the car mirror motor on a separate power supply or upgrade to a power supply that's approx 3-4 amps depending on your motor specifications Commented May 2, 2016 at 16:10
  • The slowness of the motors is likely due to a reduction in voltage and not amperage, either way, you will not really be receiving more control as your hat should be pule width modulating the feed to the motors which should give you the most control possible Commented May 2, 2016 at 16:11
  • It's still a speculative setup, at the moment it works through a USB Hub and HAT+Motor are on a separate 12V supply. But with the above, if I use the setup shown with a more powerful supply (e.g. 5V 5A) is it considered safe?
    – Tom
    Commented May 2, 2016 at 16:15
  • It should be, but only you know the ratings of your motors, just do the math for the maximum amperage required, the Pi needs about 1.2 amps, your hat maybe .5 to .25 depending on the model, then your mirror motors could be anywhere between 1-2 amps each so that's approx 4-6 amps so 5 volts 5 amps should be ok. Commented May 2, 2016 at 16:17
  • Bear in mind that you can only pump 2.5 amps into the Pi3 polyfuse. If you want more you'll need to power the Pi via the expansion header.
    – joan
    Commented May 2, 2016 at 16:32


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