However, we would like to use a very fast servo (the Align DS610: http://www.servodatabase.com/?sort=speed), which - in addition to his high speed (0.08 sec/60°) - is said to also have a higher pulse frequency than normal, namely 200hz. Thus, if I understand this right, this servo should be able to receive a new command each 5ms, instead of each 20ms (Aim I right with this interpretation?).
The table indicates that for the center position , a pulse width of 1500uS repeats is transmitted at 200 hz.
I didn't suggest there was any incompatibility. I didn't see anything about 50hz there and I don't see that it matters either way.The frequency at which the pulse is repeated is probably not critical anyway. I'm no expert in servo design but my understandingis that the pulsewidth is the critical spec because that's what changes when the servo receives commands. When you watch the servo pulsewidth on a scope , you're seeing the same 1500uS pulse with either servo. The difference is that your seeing it 4 times more often with the faster digital servos, but if you receive only one bill every month do you have to pay any more if you receive 4 copies of the same bill (one a week) during that month ? (crude analogy , I admit) but my point is that the servo must obeay a command to set it's pulse width some value whether it receives the same command 50 times a second or 200 doesn't change the command. If I have this all wrong please tell me because I do want to know. I'm just saying that is my understanding of it as it stands at the moment.
No, your are correct. The "high update frequency" servos will work fine at either 50hz or at whatever higher updating rate they are rated for.
but 120Hz is about the limit for most standard servos. This is a result of the NE544 specs (the original servo amp) that requires 6ms of "off" time between pulses.
The other thing that confuses me about the high servo update frequency is the business of multiplexing the signals for several channels for transmission between the transmitter and the receiver. If there is a 50Hz update frequency there is about 20 msecs between pulses, Since the longest pulse is a little over 2msecs there is "space" for about 8 channels within the 20 msecs.If you increase the update frequency it seems to me the "space" for multiple channels is correspondingly reduced. And I can't see any value in the receiver getting pulses at 50Hz and repeating some of them at a higher frequency on individual channels - there would be no additional data.But I may be completely dazed and confused....R