Servo Frequency

[rivers]

I know the standard servo operating frequency is 50 hz (.020 second frame rate). Is it okay to run run servos at higher and lower frequencies? Say 25 hz to 100 hz or beyond? l imagine servo current and holding power will vary with frequency. Is this correct?
rivers

[AndyKunz]

Yes - 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.

As you go slower, the torque of a standard servo drops off as the refreshing signal is what helps hold the arm against the dynamic forces. The motor is only energized (applying torque) while the signal is being sent and shortly thereafter.

Andy

[AndyOne]

Rivers,

Digital servos will take a 3ms refresh time but when i tried it with a non-digital servo, although it worked, it got really hot. I don't recommend using a significantly higher refresh rate for non-digital servos based on my experiences.

Andy.

[TheSteve]

I've used refresh rates between 60 and 230Hz.
So far the analog servos are generally fine with 90 to 100hz, I have found one model that didn't like anything higher then 70Hz. When I got too high I found they would hunt or stutter once in a while.
With digital servos I have found they all do fine with 230Hz or lower. The highest I have tried is 230Hz as that was the highest drive frequency I could safely use in a 2 channel receiver.

[erazz]

Newbee question:

How do you change the refresh rate? Would this be a change in the transmitter?

[rivers]

Andy et. al.,
Thanks for your helpful comments. Yes, I am using an analog servo. I'll try 100 hz operation. Sounds like it will work. My on-time at high frequency will only be a few seconds. My operating time at low frequency is much longer, but with very low servo loads.

erazz,
This is a non-RC application. The servo is run from a microcontroller; not a transmitter.

rivers

[TheSteve]

rivers- which servo are you using?

[rivers]

Steve,
Right now the servo is an Eflite S75, but any servo in the same weight class can be used.
rivers