What's the difference and trade-offs between a h-bridge motor controller and a mechanical speed controller for controlling a brushed motor in an RC car?

I have a cheap RC car that I'm trying to retrofit with an Arduino to convert it into a semi-autonomous robot. The car comes with a cheap mechanical speed controller, which seems to be essentially a rotary potentiometer mounted on top of a servo. The controller is also wired into an enormous resistor housed in an aluminium casing. It's motor is a brushed RS-540SH, which the specs say has a stall current of 42A, which I'm guessing is why it has such large resistors.

I could easily wire the mechanical speed controller's servo into an Arduino, but would there be any benefit to using a h-bridge motor controller instead? Based on what I know about each, the h-bridge benefits would be:

  1. completely solid-state, no slow servo or unreliable potentiometer involved
  2. ability to electronically brake the motor

while the benefits of the mechanical controller would be:

  1. it's already there and installed, so I don't need to do anything
  2. only uses a single DIO pin on the Arduino (vs 3 with a h-bridge)
  3. completely isolates the motor from interfering with all other onboard electronics

Am I missing anything?

I have a L298N based h-bridge on-hand that's rated for well over the motor's maximum voltage, but it can only handle at most 2A, which is much less than the motor's 42A stall current. Would that be safe to use, or would I be at risk of burning it out my h-bridge?

  • 1
    \$\begingroup\$ Mechanical speed controller - more detail (precise detail) needed of exactly what you mean. Just because you have a chip handy doesn't mean it should be considered given the current ratings of the motor - this device will turn to smoke. \$\endgroup\$
    – Andy aka
    Dec 23, 2014 at 8:32
  • \$\begingroup\$ One advantage of the mechanical controller : they can be quite robust against mis-use and electrical accidents. \$\endgroup\$
    – user16324
    Dec 23, 2014 at 11:07

1 Answer 1


More advantages of using an electronic controller:-

  1. Much finer speed control (mechanical controllers only have 3~4 steps)

  2. More consistent torque and rpm at low speed (PWM provides better voltage regulation than a resistor)

  3. Safer. Motor will not start if there is no signal.

  4. More efficient at part throttle (resistors waste power!).

The L298N is an old design that is inefficient and much too weak for your motor. You should either use a commercial ESC designed for RC cars (eg. Tamiya TEU-105BK) or build your own H-Bridge controller with FETs rated for a continuous current of 80A or higher.


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