Dome rotation motor

[OzDave]

I've been searching the web for a suitable dome rotation motor. I found this:

http://www.amazon.com/Wondermotor-Reversible-Electric-Gear-Motor/dp/B005LYHOMC/ref=pd_sim_misc_7

I plan to control it using a suitable driver board connected to an Arduino. The thing I am trying to work out is the current draw of the motor so I can get the correct driver board in terms of max rated current etc. I have found some boards from Pololu that can handle up to 30A.

The amazon site, and further googling for the manufacturer's site, say that the motor runs from 13.5V DC and has a rated load of 60 watts. There is no mention of current draw. However, Power = Volts * Amps, and so that implies a current of 4.44 amps.

Can anyone tell me if I am calculating this correctly? Or do I need to seek an actual current draw specification? If that calculation is correct, I assume that would be continuous operation current. However, there may well be peak currents higher than that to get the motor moving and perhaps when it brakes. Would those currents be proportional to the 4.44 amps?

Regards,

David

[Oddsocks]

Hi David,

Your calculation for normal running current is correct 13.5V x 4.44A = 60W.

The startup and braking current is not directly proportional in the sense that it depends on the inductance of the armature, the resistance of the windings, the temperature of the windings and the applied voltage.

For your intended use temperature can be ignored as long as you have some method of auto shut down or current limitation in the event of a jam (thermal switch on the housing is easiest or over-current trip on the supply)

The missing specification, maximum possible current during startup and braking is called the stall current and this can be anywhere from two to ten times the normal running current.

I checked out Wondermotor's web site but the stall current is not stated for the PN01007 motor.

I would suggest a quick e-mail to Wondermotor and ask them for the PN01007 stall current, then you will know what rating motor controller is required:

sales@wondermotor.com

William.