Power supply for motors

Hello,

Since the instructions say not to use the Raspberry Pi power supply for the Nano what should I use? I’d like to keep the microscope compact without adding more bulky stuff…

What do I use?
Thanks, Rod

I use a 1.5A 5V USB power supply. In practice you should be fine with 1A.

The reason to use a different power supply is that the Pi will take quite a bit of power (especially if you are doing images) and the motors will as well. You don’t want to have the Pi brown out when the motors turn. Having two power supplies keeps the Pi separated, and all being well stable.

This is all good advice, but I must confess that I usually use a single 2.1A supply (the official RS components Raspberry Pi power supply) to power both, and it’s fine. Those PSUs usually give 5.1V though, to protect against brown-out, and I do occasionally see the little lightning-bolt symbol that signifies throttling due to undervoltage if I use random power supplies (though it usually still works).

I think it probably is important, however, to split the motor power off before the Pi, i.e. don’t use the Pi’s 5v pin. This is because you risk blowing the polyfuse on the Pi if you draw too much current.

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I have a Canakit power supply for my raspberry pi 3, and was using a completely separate variable power supply for testing out the motors/motor controllers. I had the power supply set to 5v, but only got vibration from the motors until about 6 volts. To get the auto calibration to complete I needed to crank the voltage up to about 9.5v. Maybe the grounds need to be connected between the 2 power supplies. I have seen that be an issue for other dual power supply projects.

Hello! Are you sure the motors are 5 volts? not 12?


Mine say 5V

Last, for not thinking about motors need check resistance they coil. And comparing with 5v motor datasheet. Can measure my 5v working, but later, not at home now
my 5v motor: yellow-blue and pink-orange(5 years ago buying 67ohm, this year 44 ohm) both worked. In documentation: 5v 50ohm±7%, 12v 120ohm±7%

I discovered that I had wired the connections to the nano incorrectly. I don’t have any idea how it could have worked at all, but it did. Just give it more voltage! :slight_smile:. Correct wiring is now very quiet, not jerky, and 5v.

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Having just built some sangaboards I’ve been experimenting with the best way to power the Pi and motors. I have a 3a supply I bought to go with my pi3B (https://www.amazon.com/dp/B01N336XEU/ref=cm_sw_r_tw_dp_x_B1dnFbDN6FY9X) so figured it should be sufficient to power both.

But…if I plug the power supply into the sangaboard and use the USB-A on the sanga to power the Pi then my illumination LED flickers like crazy even when the motors aren’t running. Conversely if I plug the power supply into the PI and use one of the Pi’s USB ports to power the Sanga then it all appears to work just fine and I don’t even get the lightning bolt warning. Though I do have to connect two USB cables to the sanga - one for power one for data which is a bit annoying and makes for rather more cables than I’d expect for an integrated design.

Checking the sangaboard schematic it appears that this is correct as MOT_PWR is only Supplied from USB_Supply and J7 while USB_OTG only provides VBUS and V_USB but isn’t connected to VCC or MOT_PWR. I’m assuming this was done specifically to allow drawing more current for the motors. But since powering the pi off the sanga doesn’t seem as stable for me is a bit of a bummer.

I’ll have to do some poking at my board to see if if it’s my fault powering the pi off the sanga doesn’t seem to work better. I did have to find an alternative for D1-4 due to the specified part no longer being available. (and a few other part subs due to stock availability - though all of my substitutions should meet the same specs.)