power question - arduino, rasp pi, 2 servos

Other Hardware Motors, Mechanics, Power and CNC
1

Hi!

I am building a robot-ish project in which a raspberry pi 3b runs an arduino uno master-slave which in turn operates 2 servo motors. I have this working (mostly :slight_smile: ).

My questions are about power. I am new to this type of power question and am not sure how to proceed.

I want the whole project unit to run on batteries (I intend to run it outside away from the grid), and for as long as possible, ideally 12-24 hours at a time.

I have read that it is advisable to power the servos separately from the arduino / pi, and that in doing so the grounds should be together.

The attached diagram describes the particular items I have. Power is in the magenta blocks at the top and bottom, red lines are power, black are grounds, yellow is from the arduino pins to the servos.

Questions:

  1. Is the way the power is coming from different sources and wired here appropriate? Is this what is meant by "grounds together"?

  2. I have two rechargeable power bricks, will one or the other of them work for powering both the arduino and the pi? Should I set this up differently or use a different power source?

  3. What should I use to power the servos? Can I use one of the rechargeable power bricks, and if so, how do I distribute the power to both of the servos--that is, how do I (and should I) put USB power to a breadboard?

Thanks in advance--!

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Based on some feedback outside of this forum, I've revised the diagram (attached here) to connect grounds more thoroughly and to power the arduino and servos separately from the pi.

Will the arduino, with 12V power from the power brick, be able to support the two servos?

Would it be better to power the servos directly from the same power brick as the arduino (rather than through the arduino), and if so, is there a best-practices way to do this?

Thanks much!

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NeilHLN:
Will the arduino, with 12V power from the power brick, be able to support the two servos?

No. The Arduino can control the servos, it cannot power them. The servos need to be powered directly from a power supply of appropriate voltage. Rule of thumb is to budget 1A per hobby servo - may of course be more for bigger devices.