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Old 03-09-2008, 05:10 PM   #1
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Default DIGITAL SERVO

Can someone tell me what is the difference between a digital servo and a standard one.

Thanks
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Old 03-09-2008, 05:33 PM   #2
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About 30 bucks
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Old 03-09-2008, 05:40 PM   #3
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Thanks but I don't mean in price I mean in performance if there is any.
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Old 03-09-2008, 05:44 PM   #4
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This is a pretty good explanation.

http://futaba-rc.com/servos/digitalservos.pdf
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Old 03-09-2008, 05:45 PM   #5
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In general, they are more responsive, have finer steering inputs, and have more torque. These are just generalizations.

Some digital servo's require the use of certain types of receivers or radios to take full advantage of the servo.
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Old 03-09-2008, 07:07 PM   #6
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Digital servo's also have a more accurate "return to zero" point. Higher holding power and more precise working. They DO require an FM radio and will NOT work with AM radio sets...

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Old 03-09-2008, 07:15 PM   #7
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Quote:
Originally Posted by Joost K. View Post
Digital servo's also have a more accurate "return to zero" point. Higher holding power and more precise working. They DO require an FM radio and will NOT work with AM radio sets...

Joost.
Why don't they work with AM? Is it because of interference, due to their higher/stronger switching frequencies?
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Old 03-10-2008, 06:15 AM   #8
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Interresting question. After your reply I have searched on the sites of the four major manufacturers and guess what. There is no information on this subject. I own three digital servo's from Futaba and in the ducumentation of these servo's there is only some info about the transmitters they will not work with and they are all AM transmitters. It is even so that with the HRS system from Futaba ONLY digital servo's can be used. But I couldn't find anything anywhere why that is...

Maybe somebody knows...

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Old 03-10-2008, 07:20 AM   #9
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I only think AM has the problem that it has (mostly) a BEC system which can not handle the current loads a digital servo wants. I have seen digital servo's work on AM systems....

HRS is simple to explain. An analog servo is set to a pause of about 15ms to listen for the next information pulse. With HRS where the pulse comes once in about 5ms and analoge servo will loose the synchronisation.
Digital servo's are not set to a pause, after getting their pulse they are directly ready for the next pulse.
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Old 03-10-2008, 07:30 AM   #10
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Isn't the BEC system something that is inside a ESC? BEC stands for Battery Eliminating Circuit and was created not to use a seperate receiver battery. That has nothing to do with the modulation of the transmitter. Yes, most digital servo's require 6V and most BEC systems on ESC's don't provide that voltage but still they work. It is just that the booklets of the digital servo's say that they can't be operated with an AM system. But there are no arguments on why this is.

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Old 03-10-2008, 10:03 AM   #11
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I think that Futaba link does a pretty good job of explaining the benefits of digital servos. So the same reason they are better is probably the same reason they cannot work with some AM radios. The sampling rate is just too slow on those AM radios and the digital servo's sampling rate is high enough that it loses the signal for the cycles that are in between those of the radio.
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Old 03-10-2008, 10:12 AM   #12
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AM and FM do give the same servosignal with the same timings.
It must be the power or interference.
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Old 03-10-2008, 01:35 PM   #13
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It works with most AM, FM and DSM radios. As Roelof said, the signal is the same (except high rate Rx). So it must be interfernce if you have a problem.

The exceptions are that you shouldn't use analog servos with a high frame rate radio, i.e. Futaba HRS.
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Old 03-15-2008, 10:23 AM   #14
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digital servo is better in every way only advantage with analog(regular) servo is that, say in always perfect conditions an analogs lifespan will be longer. in normal racing conditions digital all the way.
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