[NSRCA-discussion] Servo Signals

[James Oddino]

They are called digital because they use digital techniques.  The  
transistors are either on of off.  As far as I know Jerry Pullen was  
the first to build them and this was his explanation.  Doug Spreng who  
worked with Jerry at JPL was the first to produce and sell a system  
with them (Digicon).  Many improvements were made through the years  
and eventually JR made what they called a Super Servo that contained a  
microprocessor.  This led to the modern day "Digital' servos that also  
contain microprocessors.  At that point all the previous digital  
servos began being called analog.  The truth is they are all analog  
and the basic concept has never changed.  The input is a pulse that  
varies in width from 1 to 2 milliseconds and the output position is  
proportional (analogous) to the pulse width.  A true digital servo  
would be sent a binary coded input (ones and zeros) like a PCM  
transmitter sends to the receiver.

Hope this helps, Jim



On Jun 23, 2009, at 5:03 AM, Vicente Vince Bortone wrote:

> Jim,
>
> I don't know anything about electronics.  I am sure that the  
> following question if very simple for you:  Why the digital servos  
> are called digital?
>
> Thanks,
>
> Vicente "Vince" Bortone
>
>
> ----- Original Message -----
> From: "James Oddino" <joddino at socal.rr.com>
> To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
> Sent: Tuesday, June 23, 2009 12:12:23 AM GMT -06:00 US/Canada Central
> Subject: Re: [NSRCA-discussion] Servo Signals
>
> What do they say in the Capital 1 commercials, not literally?   
> Transmitters communicate with receivers digitally in PCM mode and  
> analog in PPM mode.  Receivers communicate with servos analogy (?)  
> with PWM.  The servos are analog.
>
> Jim O
>
>
> On Jun 20, 2009, at 7:23 PM, Bob Richards wrote:
>
> --- On Sat, 6/20/09, Richard Lewis <humptybump at sbcglobal.net> wrote:
>
>
> And....Interestingly enough.....It does not matter what kind of  
> fancy whopping digital super latest and greatest TX/RX system you  
> have, the signals to the servos are still firmly rooted in good old  
> 1970's technology....:)  And...Your super whopper digital brushless  
> whatever servo still has an analog pot for position feedback....:)
>
> I for one am eager to see a leap in servo  
> technology.....Bidirectional serial comms to the servos with the  
> servo being able to feed back torque, amps, position, rate,  
> etc.....and encoder/resolver position feedback in the servos to  
> really catch up with the world we live in......
>
> Amen to that. We have digital servos and digital receivers, yet they  
> talk to each other via an analog method and use analog feedback.
>
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