[NSRCA-discussion] Servo Signals

[James Oddino]

True.

On Jun 23, 2009, at 2:01 PM, John Pavlick wrote:

> Actually the VERY early R/C systems were truly digital as far as the  
> controls went. The escapements drove the surface either neutral or  
> full left, etc. Galloping Ghost just had more "bits". :)
>
> The fact is that we want the control surfaces to move in an analog  
> fashion. Regardless of how the servo determines and maintains it's  
> position. We live in an analog world.
>
> John Pavlick
>
> --- On Tue, 6/23/09, James Oddino <joddino at socal.rr.com> wrote:
>
> From: James Oddino <joddino at socal.rr.com>
> Subject: Re: [NSRCA-discussion] Servo Signals
> To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
> Date: Tuesday, June 23, 2009, 4:51 PM
>
> 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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