Circuit 9v with multiple motors HELP please.

Hi Everyone

I'm new and not really a great electric guy! I need a little help here.

I have a project in mind, I want to power 5 medium motors and 3 large motors with the same power supply or mabee 2. Power supply that I want to use is a 120 VAC 60 Hz 8W to 9VDC 600 mA

Motors specs:

Medium Motor. It delivers a maximum torque of 40 mNm (300 mA). The current consumption will depend heavily on the load it is driving. Under normal conditions it can be around 150 mA

Large Motor. It delivers a maximum torque of 45,4 mNm (450 mA). The current consumption will depend heavily on the load it is driving. Under normal conditions it can be around 225 mA

Everything is connected from the source of power at the same place.



Look at the power rating (W) of your motors, sum them up to get the required power of your power supply and the current.

The “normal conditions” only are for guessing battery life time, but a power supply should be rated for the maximum (stall) current of the motors.

Thanks for the reply

Stalled current is 850mA for the medium motor and 1.3A for the large.

I found a table on the motors power rating here:

PF medium and PF large

So I can get a 12v power supply with a max 2.7A and I will not burn anything if I sum all the motors. I will need 2 with this setup. Nowhere I can find the output power rating on the adaptor ??? it only said that:

So If I sum 3 larges it's 3.9A so anything under that should do the job but not too lower because they not gonna have enough current.

in: 100-120V AC, 47/63 Hz
out: 12V DC, 2.7 A

I am so confuse... I don't have a lot of choice in power supply a decent price.

Do you know the difference between voltage and current?
What's the nominal voltage of your motors?

You risk to burn the power supply if it cannot source enough current.

You also risk to burn the motors with a too high voltage, unless the motor driver module allows to limit the motor current.

You can't really run 9V motors on a 12V supply. If you do they will take more current and possibly burn out. You need a 9V supply.

5 x 850mA = 4.25A. 3 x 1.3A = 3.9A. So to safely run all motors on one supply you need 9V at 8.15A. Because you probably won't have all 8 motors stalled at once you can probably get by with a little less. 9V at about 6A will probably work.


all 8 motors stalled at once

Which is equivalent to trying to start them all at the same time! Stall current = start-up current. So that's another thing: if there's a need to start them at the same time you still need to be able to supply full stall current.


YEah I know the difference between current and voltage. MY motors can take 9v to 12v. I get it if I sum the current of all motors it will give me the current max. But what abouT the power rating? It is not specified anywhere on the power supply?

The only electronic shop near my home is this :

I can found at a decent price a 9v 600mA or a 12v 2.5A. Not really other choices that are decent.