# Powering multiple concurrently running micro DC motors

I have a small raspi controlled remote control car using regular drone motors such as these ones and tried using this 60w power supply unit that can be downregulated to 3v and connected everything using two drv8833 motor drivers. However, the spikes in power drainage generated from one motor alone seem to be enough to drain the entire amperage of the circuit, in spite of each motor only consuming 0,15a. Is there a reason for this?

It's possible that there is some additional resistance when the motors start up causing them to drain more than the specified 0,15a, I am not using any gears but the car itself is very light so I don't think the spike in amperage drainage justifies all the other motors completely stalling when the power source is said to provide 60W.

The current limit for the DRV8833 is 2A, I am using two of those modules with each having two motors connected to them.

Is there a good solution to this problem? I tried placing a 3.300uF 6.3V capacitor around the motor driver but am still having problems with only one of the motors actually starting up

Here is what my setup looks like:

• Yes - Hi, Can you Edit your question to answer the points below: Add photos showing the h/w & wiring e.g. between motors & motor drivers, and between power supply & motor drivers etc. | In your country, is comma the decimal separator and period the thousands separator? | Add photos showing where you added the capacitor. | How & where did you measure the motor current? | Do you have an oscilloscope? | How did you decide that it was current drain from one motor causing your problems and not (for example) EMI from that motor affecting your RasPi? Have you checked the RasPi is not rebooting? Aug 13, 2021 at 14:00

It's possible that there is some additional resistance when the motors star

Extra resistance does not drain current.

in spite of each motor only consuming 0,15a. Is there a reason for this?

Motor current varies with load and speed and startup currents are basically stall currents. In other words, the 0.15A is an average current under specific operating conditions. It is a current draw, not the current draw.

You can't measure peak currents with a multimeter which only gives an average. You need a scope that can graph out instantaneous current over time.

I tried placing a 3.300uF 6.3V capacitor around the motor driver but am still having problems with only one of the motors actually starting up

"Around the motor driver" does not tell us how you actually connected the capacitors.

But if they are across the power pins of the driver IC as they should be, 3.3uF is nothing for a motor. You need at least 100uF.

• Hi, Notice where the OP used a comma ("0,15a"), so where they wrote "3.300uF" and you responded "3.3uF is nothing", I suspect that the OP is from a country where the comma is the default decimal separator (hence "0,15a") and the full stop (period) is the default thousands separator. So, pending clarification from the OP, I think we should consider that the OP probably intended to say 3,300 uF when using the comma as a thousands separator (i.e. 3.3 mF). Agreed with all your other points. Aug 13, 2021 at 13:51
• @SamGibson Well 3.3mF might prevent the power supply from starting up being too big due to startup inrush. Aug 13, 2021 at 14:23
• @SamGibson Most 100uF capacitors state a voltage of ~100V, is that normal and still useful for a 3v circuit? I have added a picture so you can see what my current setup looks like with one motor driver
– Yes
Aug 13, 2021 at 15:04
• @Yes They will just have higher ESR, all other things equal. Fine for motors. 100V is high though for being common. 25-50V is more common. Where are you getting your caps from? Aug 13, 2021 at 15:08
• is 100 fine for this purpose? Do you also know how I can calculate how many capacitors I would require if i were to want to power more than four motors at once using the specified motor drivers? My solution so far has been connecting a seperate usb power supply to each one, but if I were to want to only use one source would the one I specified be enough?
– Yes
Aug 13, 2021 at 15:12