# Amperage

Hi all, are these little 5v DC motors that come with the kit really pull 8.3amps? According to my calculations 5v/0.7=8.33
I didn't realize it was that much at full speed.

A DC motor draws its maximum current when the motor is stalled. The stall current could easily be 10 times the running current. It would be wise to assume that a motor will overheat and destroy itself very quickly if it is stalled though you can get motors that are designed to be stalled.

...R

The current in a DC motor depends on the torque the rotor is applying to the load (and friction).

An unloaded motor will pull very little current (except briefly as it starts up).

I'd strongly suggest not powering any motor from the logic 5V supply, motors put voltage
spikes on the supply and you don't want to endanger the Arduino board. Share grounds
and use a separate supply if possible.

What is the 0.7?

al514:
Hi all, are these little 5v DC motors that come with the kit really pull 8.3amps? According to my calculations 5v/0.7=8.33
I didn't realize it was that much at full speed.

0.7 ohms is that? That's a bit low for a small toy motor, some I have are about 6 ohms.

But yes, motors pull a lot of current at stall (the current is much much lower at full speed unloaded
as the rotational back EMF cancels the applied voltage mainly).