davewbrwn
Posts: 2
Joined: Mon Dec 16, 2019 6:51 pm

How to power a Raspberry Pi and servo motors with one power supply

Mon Dec 16, 2019 7:01 pm

I'm building a robot using Raspberry Pi and several servo motors. I'd like to power all components using a single lithium ion battery. I've looked into using a motor driver hat, but it seems the motor hats are unable to power the pi, so two separate power sources are required. Can anyone provide advice on how to best achieve my goal of powering the pi and all motors from one power source? Thanks!

wolf.z
Posts: 131
Joined: Thu Dec 24, 2015 8:34 pm

Re: How to power a Raspberry Pi and servo motors with one power supply

Mon Dec 16, 2019 7:19 pm

Hmm, some more details would be quite helpfully. That said, e.g. the servo as well as the motor driver hat from waveshare suggest to provide a 5 Volt voltage converter, fed by the 6-12Volt Battery In.

emma1997
Posts: 502
Joined: Sun Nov 08, 2015 7:00 pm
Location: New England (not that old one)

Re: How to power a Raspberry Pi and servo motors with one power supply

Mon Dec 16, 2019 10:05 pm

I found reliable operation in cases like this needed at least a 2s battery with couple buck converters. One for Pi and one for the motors. They are very cheap from china (as low as 5 for a dollar). Attempts to use linear regulators or one cell with/without boost converters eventually failed.

Quite a few noobs here insist one cell works fine but either eventually switched to two or just disappeared. For non-critical apps it's fun to play around but if something needs to actually work better than "some of the time" then good electrical engineering practices may be worth investigating.

davewbrwn
Posts: 2
Joined: Mon Dec 16, 2019 6:51 pm

Re: How to power a Raspberry Pi and servo motors with one power supply

Tue Dec 17, 2019 1:12 am

emma1997 wrote: I found reliable operation in cases like this needed at least a 2s battery with couple buck converters. One for Pi and one for the motors. They are very cheap from china (as low as 5 for a dollar). Attempts to use linear regulators or one cell with/without boost converters eventually failed.

Quite a few noobs here insist one cell works fine but either eventually switched to two or just disappeared. For non-critical apps it's fun to play around but if something needs to actually work better than "some of the time" then good electrical engineering practices may be worth investigating.
This sounds promising but how do I split power from the battery to the two buck voltage converters?

emma1997
Posts: 502
Joined: Sun Nov 08, 2015 7:00 pm
Location: New England (not that old one)

Re: How to power a Raspberry Pi and servo motors with one power supply

Tue Dec 17, 2019 3:02 am

Simply wire both of them to the battery (in parallel). It's the converters that do the 'splitting'.

If there is a DC supply or other source available then a penny diode inline with each will automatically and instantly select the higher. So if DC quits battery will take over and versa vice. Poor man's UPS at about 1% the size and cost of a commercial unit.

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