Sensing RC receiver impulses & PWM motor control
Scott Stephens email (remove spam text)
>I'm looking for some code (preferable with application notes for the circuits)
>concering radio control and motor control - preferable with PICs (but no
The Circuit Cellar BBS (860) 871-1988, has the file SERVOPIC.ZIP in File
Area 1 from the October 1994, Issue #51
magazine. You may be able to get it from their web site. The code is for PWM
>1. Decoding the servo impulse/s from a RC receiver:
> * preferable a 'self learning' application
> * determination of multiple levels of modulation (centre, and max. would
> certainly be of help for the beginning)
> * 'fail save'-state whilste there is a signal loss/no signal
It might be better to use PIC to modulate and demodulate your signal,
tapping the receiver's comparator output and your transmitters modulation
input. That way, you can employ error detection and correction codes in
>* What is the best way to do multiple tasks with a PIC (esp. 16C84)?
> Ex.: In a motor controller I would have to watch for the incomming impulses
> whilst pulse width modulating a motor, sensing the current, etc.
> To bad if I'm stuck in a wait loop... (If you know what I mean :-)
> Since I want to use the 84 - How do I put the interrupts to best use?
Read Microchip's AP-Note AN-585 "A real-Time Operating System for PIC16/17".
Read about state-machine design in a textbook. The April 92 Computer
Applications Journal has a good article on state-machine design.
> What's the best way to measure the Rds[on] with hobbiest equipment
> (some DVMs [not acurate in mOhms-Measuring], Scope [10MHz])?
I would observe the voltage drop across the FET, motor and batteries in
operation. Then use the series current to determine where the power is going.
I'm interested in a good power FET too. I don't like high-side drives &
See also: www.piclist.com/techref/io/motors.htm?key=motor
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