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I am building a 4 leg robot with a Raspberry Pi and 8 servos (Amazon product page).

Currently I have a a 6 V 3A power supply powering the servos through a 5V 5A buck converter and a 5V 2A power supply for the Raspberry Pi.

This set up works great but I would like to lessen the weight on the robot by using one power supply to power both components. I'm new to electrical things and was wondering how do I determine what the power requirements are to power all the servos and raspberry pi with one battery? Do I just need to increase the amps?

Marcus Müller
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grarawr
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  • so many duplicates of how to choose a power supply; but yes, you just add up the current draw of your components and that gives you how much your supply must at least be able to supply. – Marcus Müller Apr 13 '20 at 19:51

2 Answers2

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Power is a combination of voltage and current.
For choosing the voltage specification of power supply, find which component requires the maximum power by calculating their operating voltage and current consumed by them, take that voltage.
Since both the servos and the Raspberry Pi work at 5V, go with 5V supply.
Now, since you have fixed the voltage parameter, you need to choose the current specification.
Calculate the total power consumed i.e. the power of servos (5*current) and power of Raspberry pi (5*2.5=12.5W).
Considering high efficiency of power converters, divide the power you calculated by the voltage you just calculated to find current (Power/Voltage=Current).
Once you have calculated the current, assume your power supply will be 80% efficient. Calculate actual current needed using Current/0.8, since actual current*efficiency=output current.
Thus, you need a voltage of 5V and current of 3.3/0.8=4.125 close to 5A (assuming 100mA current consumption of each servo).

Edin Fifić
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SOUHARDHYA PAUL
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Because both things require 5v, using a single supply or battery for the servos and the Pi would seem to be fine. However, if your battery or power supply cannot provide enough current (amps), when you are driving the servos at full, the current to the Pi might drop and cause the Pi to reset. I suggest having two batteries - one for the servos, and one for the Pi. That way, the Pi can monitor the servos and supplies and potentially alert when the batteries get low, or go into a lower-power mode, or things like that. Plus, then if you need to swap batteries to keep running, it wouldn't require that the Pi be rebooted. Li-po batteries are what you'll want to supply that kind of current consistently.

async8192
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