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Battery power for my Pi
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Please be positive and constructive with your questions and comments.

Battery power for my Pi

by edmdavis11 on Wed Feb 10, 2021 11:02 pm

My students will be making Raspberry Pi controlled robots using an L298N board and a couple of motors (motor power is 6-9 V from batteries). We will program the bots with Mu on the Pi but then would like to unplug the Pi from line voltage and run it using rechargeable batteries - this way the robotic cars can move freely. My sources say I need to be very careful to protect the Pi from unstable voltages/current. I am sure you make a board for this but I cannot find it. What do you recommend? I will need a class set of them so expense is a concern.
Thank you!!
Ed

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Re: Battery power for my Pi

by dastels on Thu Feb 11, 2021 11:18 am

Yes, your big concern is keeping the high frequency noise generated by the motors away from the Pi. That could be by using a separate power supply for the motors, or you might get by with aggressive decoupling capacitors.

The DC/Stepper motor hat is one option: https://www.adafruit.com/product/2348. It uses a separate 12v power for the motors.

Another possibility is the Crikit hat: https://www.adafruit.com/product/3957. It's powered by 5v (USB or a barrel connector) and is a better alternative for a mobile project (smaller, lighter battery). As designed, the Crikit 5v is used to power the Pi, but removing a couple diodes would isolate it (and you'd have to power the py separately. See https://cdn-learn.adafruit.com/assets/assets/000/067/685/original/circuit_playground_schem1.png?1544825013, diodes D1 and D4.

The Crikit also has he advantage of having quite a bit of other I/O and is available in other formats as well (CircutPlayground and Feather).

The Crickit hat currently lists for $35 and the motor hat (and a bonnet version) for $23.

A more barebones approach is to use a DRV8833 breakout https://www.adafruit.com/product/3297. It's not as plug and play but will control 2 motors. One big downside is that you need to provide it with PWM signals for motor control. On the Hats, those are generated on board and you only need I2C to control everything.

For robotic projects, I like the Crikit. That's what it was designed for, afterall.

Dave

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Re: Battery power for my Pi

by dastels on Thu Feb 11, 2021 11:20 am

I neglected to address the battery itself. I've used a 6600mAh Lipo https://www.adafruit.com/product/353 and a PowerBoost 1000C https://www.adafruit.com/product/2465 suggessfully.

Dave

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Re: Battery power for my Pi

by edmdavis11 on Thu Feb 11, 2021 12:25 pm

Hi Dave,
Thanks for the information. Maybe a bit above my meager knowledge base and I probably wasn't super clear in my first post. I currently have everything I need to power two motors (separate battery pack and an L298N motor driver board). We can get our motors to spin and can control them with Python through the GPIO pins!! For us, this is a big accomplishment!
What we would like to do now, is to unplug the Pi from the wall and power it with batteries. In this way our robotic car will be free to roam about and the Pi will have its own power supply.
What I am looking for is a 'plug and play' power converter so that I can run the Pi from a battery pack. Thanks a lot for your help and sorry for the confusion.
Kind regards,
Ed

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Re: Battery power for my Pi

by edmdavis11 on Thu Feb 11, 2021 1:00 pm

I think what I am looking for is a DC to DC step down convertor. Does that seem correct? Will it work with the Pi and protect it?

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Re: Battery power for my Pi

by dastels on Thu Feb 11, 2021 2:55 pm

Sorry about that. A buck convertor would do the job if you have a battery > 5v. https://www.adafruit.com/product/4739 might do it if your current requirement for the Pi is less than 1.2A

Dave

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Re: Battery power for my Pi

by edmdavis11 on Thu Feb 11, 2021 3:01 pm

Thank you very much and again sorry for my confusion.
Ed

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