Controlling high current motor

Hey there

i have a rear axle from a Electric scooter, and want to build a remote controlled thing.. but iam not an Expert, i need a controller to ajust motor speed, and a remote controle unit to controle the motor.

my motor is 24V and around 15-20A and the remote, i need to controle motor speed, forward and reverse, and stearing, and some asosseries, i have looked at some arduino Projects about remote with xbee, but i dont know if this will be the right solutions..

i hope that someone in here, can help me in the right way, and what to do..

//Brian Denmark

You need a 500 Watt (24 V * 20 A + some margin) motor controller. A Google search should turn some up.

First work out the stall current, ie measure the resistance R of the motor and calculate stall current = 24V / R.

To measure a low resistance like this you have to pass a known current through it and measure the voltage across it at the terminals of the motor - this is called a 4-terminal Kelvin measurement. Just using a multimeter will probably just measure the resistance of its leads!

The stall current is what's going to flow in any sudden change in drive level to the motor and the driver circuitry has to be able to withstand it. For instance if the stall current is ~200A then a 50A controller is probably going to explode its MOSFETs.

A good controller will have fast overcurrent shutdown, which will make it robust, but it will simply cut out all the time if its underrated.

Careful smooth control of the drive level to the controller will reduce large current peaks though, since the motor has a chance to change speed.

If you power source (battery?) is weak it will limit the current peaks itself, but at the expense of wasted capacity and internal heating.