[mowbot] PWM

Michael Davenport (michael.davenport nospam at wheatstoneenergy.com)
Wed, 2 Jun 1999 21:44:06 -0400

Someone please suggest a good reference for designing and building PWM speed

I bought myself a Nikkon RC Jeep real cheap from Tower Hobbies on-line.
Well, It's not the normal servo-transmitter type RC car. It's AM 2-channel
radio is purpose built and it only has 7 functions: full go, full stop, full
reverse, full go with full right turn, full go with full left turn, full
reverse with full left turn, and full reverse with full right turn.

Well as usual, UPS tore it up pretty good in shipping. After some necessary
modifications it's running and about to donate its guts to my lawn mower
project. I also have a 27 MHz AM radio set (a four-function type) I bought
from Radio shack many years ago. (Cat. No. 277-1012)

Anyway, I guess I'll use one set of radios to make it go or stop, and the
other set to control the speed, and/or the amount of steering. Maybe with
one pistol grip type transmitter (a trigger speed control and a knob
steering control) the trigger can be designed with two coaxial transmitters
(one that sends signal "go" for any position other than center (turns the
drive motor(s) on), and the other that sends the PWM signal to control
speed) - This way I can pull the trigger slightly and it will beging to
creep along, but the further I pull, the faster it will go. Same goes for
the steering except it will operate from the knob above the trigger.

Can you PWM a 12VDC window winder motor all the way down to zero RPM? How
'bout up to full speed, or even slightly overdriving it? (like 118 RPM on a
100 RPM motor) - Or do you just want to PWM down to 10 RPM or so and then
just stop.

What about the electronic speed controllers sold for use in high end RC
cars - are they PWM units?

Am I on the right / wrong track?

Michael Davenport