What power supply is required for my project?

Hello everybody!

I am using 3 DC motors as well as a TowerPro Microservo 9g. Each of the dc motors require 12VDC power and approximately 300mA current. The microservo i would guess has both very low power and current consumption. I am also using a Myoware muscle sensor which uses about 9 volts.

The question is: what power supply would be sufficient for using all of these simultaneously? How many volts would the power supply need to be?

If someone could recommend me to a proper DC power supply that would be sufficient for these specifications, it would be greatly appreciated!


The highest voltage you need is 12V so get a 12V brick. But you also have to step it down for the Myoware sensor because you say it uses 9V. Depending on the power consumption of it (which you didn't give) you can use a lineair regulator or just go for a DC DC step down converter. They are dirt cheap nowadays anyway.

Then the servo, your guess is a bit off. Depending on the load and speed you turn them they can draw up to an amp with ease. And it needs 5V so another regulator. Because of the power I would grab a DCDC step down converter.

So overall, guessing the Myoware isn't really power hungry, I would grab something of a 12V DC with an minimal rating of around 2A. Where to buy it depends on how quick you need it and what you're willing to pay. Sometimes you can find one in a thrift shop or you can go online. Something like this is not to bad.

DC motors don't require a certain voltage -- the 12V you state is probably the recommended maximum. They just run slower and provide less power at lower voltages. 9V should be fine.

Also, the 300 mA figure is misleading, as it depends entirely on the load. You need to know the stall current and provide for that in your motor driver, as it is typically 5-10 times the "typical" running current. Brushed DC motors briefly draw the stall current every time they start up.

For a typical servo, plan on 5V at 1 ampere current and you will usually be safe. You will need a regulator to run the servo from a higher voltage power supply. Do not "guess" that the microservo has "both very low power and current consumption" -- look it up on the product page.

Finally, don't run motors and the Arduino+sensors from the same power supply. That will only cause trouble. For muscle sensors you usually want to run from batteries. Be sure to connect the grounds.

These are the motors motors, microservos, and muscle sensor (check the manual for the muscle sensor).

So from your responses, I gather that I can use a 9v battery for the muscle sensor, a 12 volt power supply for all the motors, and the arduino's power (coming from a 9v power supply) to power the microservo.

Is this correct? Or would I be able to use just the 12v power supply to the arduino, and from the arduino, i could power a breadboard for the motors and microservo, and just get the 9v battery for the muscle sensor?


Never power a servo or motor from the Arduino. You will have nothing but trouble.

Never power a servo or motor from the Arduino. You will have nothing but trouble.

Often true, especially if running the USB to the Arduino from a laptop and tablet which have less USB power available. In classes where I have students (try to) run those 9G MicroServos they are usually OK if the USB is run from a desktop machine or from a plug-in 5V 1A USB supply. But laptops and tablets often don’t make it.

I like this low-cost overall solution for many experiments: an external 9V or 12V “wall wart supply” for $3 to $5 and an Arduino-compatible with built-in 5V 2 A switching supply like This RoboRED:

** DISCLAIMER: Mentioned stuff from my own shop… **

I usually use a 12V 1Amp wall supply plugged into the External Power jack on the RoboRED, and use the USB at the same time for uploading. This will run 4 or 5 servos or small stepper motors. (Try to code so all the servos do NOT start a big move at the same instant! Stagger the start or use acceleration).

What terryking228 is true. But also don't try to power servos/motors/heavy load from an Arduino with a wall wart plugged in. The normal/real Arduino can't handle that.

The RoboRED looks nice and all but it's still an order more expensive then a Uno + DCDC (or 5) from China. But okay, China, so not a real fair comparison.