Using DC motors with RC Robots

[Murari]

I am building an RC robot/boat and wondered if Servos are really required for the propulsion systems. To power the propellers i had thought of using normal DC motors but in the many posts i have read, i have seen mentions of only servos being used. I wanted to know if I could use a DC motor instead and what the constraints are in using DC motors with an RC mechanism.

[hgordon]

The main issue is that you'll need a different type of control circuit - servos are driven with a timing pulse that typically ranges from 1.0 - 2.0 milliseconds every 20 milliseconds, while DC motors are driven by a continuous pulse stream called Pulse Width Modulation (PWM) with a varying duty cycle (0 - 100%).   You'll need an h-bridge or a set of MOSFET's to switch the current going to the motors, while no interface circuit is generally required for servos.

There might already be a tutorial on this site about interfacing to servos vs DC motors.

[Admin]

typically i strongly recommend servos just because they are so much easier and cheaper than any other option out there.

but in your case, you require high speed . . . you will need to get a motor driver and hook it up to your motor . . . there are some motor drivers out there that let you control DC motors as if they were modified RC servos (meaning they take RC signals from your microcontroller or RC reciever and output the required PWM for your motor).

this does such as task, and im sure there are others out there:
http://www.dimensionengineering.com/Sabertooth2X10.htm

[silent tone]

there are some motor drivers out there that let you control DC motors as if they were modified RC servos (meaning they take RC signals from your microcontroller or RC reciever and output the required PWM for your motor).

this does such as task, and im sure there are others out there:
http://www.dimensionengineering.com/Sabertooth2X10.htm

Is there a difference in this device from normal RC speed controllers?  There are a large selection of those, though most only drive a single motor.

Tony

[Admin]

Is there a difference in this device from normal RC speed controllers?

efficiency, audible noise (badly designed controllers cause your motor to hum), maximum voltage and current draw, plus other features differentiate the controllers . . .