Hi Ariel,

It IS actually PWM, just PWM where the maximum "on" time is not 100%
of the period. The frequency is usually around 50Hz, and the "on" time
varies between 1 and 2 milliseconds (which would be 5 and 10% duty
cycle).

The signal received by the receiver is PPM encoded, but the receiver
converts this into PWM for each servo. Note that unlike regular PWM,
this is not used to directly drive a motor but rather to send a
command.

Sean


On 5/6/07, Ariel Rocholl <arocholl@gmail.com> wrote:
> Minor correction: PPM for RC is pulse "position" (as opposed to width in
> PWM) modulation.
>
> 2007/5/6, John Ferrell <johnferrell@earthlink.net>:
> >
> > The radio output of an RC receiver is a pulse. The width of that pulse
> > determines the servo position. The accuracy and repeatability as well as
> > the
> > output power are reflected in the price of the servo. You can either work
> > from that pulse OR use a high quality servo of your choice to turn a knob.
> > Most of that kind of setups balance a bridge.
> > The chips in the servos have all been unobtainable by me!
> > Good luck...
> >
> > John Ferrell    W8CCW
> > "Life is easier if you learn to plow
> >       around the stumps"
> > http://DixieNC.US
> >
> > ----- Original Message -----
> > From: "Bob J." <rocketbob@gmail.com>
> > To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> > Sent: Friday, May 04, 2007 9:17 PM
> > Subject: [PIC] r/c receiver interfacing
> >
> >
> > >I am looking to build what is essentially an a huge radio-controlled
> > servo
> > > with a stepper motor.  In order to drive the stepper motor, I have to
> > > convert the r/c receiver's pulses into step/direction pulses.  To my
> > great
> > > surprise I googled for something off-the-shelf to do this, but have come
> > > up
> > > empty-handed.  Has anyone done this sort of thing?
> > >
> > > Regards,
> > > Bob
> > > --
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> > >
> >
> >
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>
>
>
> --
> Ariel Rocholl
> Madrid, Spain
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