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50 Amp Model Motor Speed Controller - With Brake

It fits in a tiny plastic case, can handle motor currents up to 50A and is compatible with existing radio control gear.

By Ross Tester and Branco Justic

The obvious question is who could possibly want a controller capable of such huge currents? After all, your typical radio controlled model, say a race car or buggy, has only a 7.2V battery and a 75W motor – ergo, 10A.

For this project, we’re not talking your typical off-the-shelf radio controlled car or buggy. We’re talking industrial-strength models powered by, say, 12V motorcycle or even car batteries. Large boats, electric-powered planes and big cars and trucks, for example.

Click for larger image
Housed in a tiny plastic case the motor speed controller is small enough to fit into the vast majority of models. The 3-wire rainbow cable on the left connects to the radio control receiver servo output while the wires on the right connect to a battery and the motor. You will probably need thicker cables. Note the six MOSFET tabs emerging through the case lid.

At the opposite end of the scale are competition boats, cars and planes which may not be very big but have very powerful motors demanding a lot of electrical power.

They might draw 10 or 20A or more on load and therefore need significantly more in the controller department. But 10 or 20A is a far cry short of 50A.

Why the brute strength? Couldn’t we make it a bit simpler and save a few bob? Yes . . . and no!

The problem lies not so much in the typical load current of the motor, nor even the start-up current (which can be high). It lies in the stall current. A motor loafing along at 10A might draw ten times as much if locked up – for example, when the car it is pushing hits an obstacle and before the wheels start slipping.

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