On 11/08/2011 05:04 PM, Jon Elson wrote:
> No, RC is a pulse POSITION modulation, see
> <http://skymixer.engineering.free.fr/index.php?option=com_content&view=article&id=74:rc-ppm-signal&catid=51:rc-receivers&Itemid=49>
> for more info. (Line may have to be unwrapped.)
Jon,
it depends on where you are looking at.
In an RC system for model plane, if you look to the RF modulator input, you are
right (first row of
schema you posted).
But if you look to each servo control wire (the original topic of this thread),
then the information
position is coded with the pulse width.
Really that depends from the original Phil Kraft design and implementation
(dated middle '60 if I
remember well).
The _recent_ RC servos are quite forgiving of the frequency of this pulse: the
more advanced ones
have a microcontroller inside in order to drive the electrical engine to a
quite high PWM frequency
and get lesser losses.
That was not necessarily true in the past though, because the old RC servo
circuits heavily depend
on the pulses period of 20-30 ms in order to correctly drive the small engine
inside.
*am*
---------------------------------------------------------
Andrea Montefusco iw0hdv http://www.montefusco.com
tel: +393356992791 fax: +390623318709
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