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DynamoBen
05-31-2009, 12:13 PM
I'm been thinking/planning some additions to my display that will require servo control. Everything I have seen about servos seem to indicate that servo cables (+5, com, data) should be no longer than a couple of feet.

If this is really the case that means I need to put controllers locally at each prop (keeps servo cable length down). However, if itís safe/usual to allow cable lengths 10 feet and beyond then I could use one central controller and save some money.

Are there specs for max cable length? Am I correctly describing the limits of servos and their architecture?

RPM
06-01-2009, 12:00 AM
I'm been thinking/planning some additions to my display that will require servo control. Everything I have seen about servos seem to indicate that servo cables (+5, com, data) should be no longer than a couple of feet.

If this is really the case that means I need to put controllers locally at each prop (keeps servo cable length down). However, if itís safe/usual to allow cable lengths 10 feet and beyond then I could use one central controller and save some money.

Are there specs for max cable length? Am I correctly describing the limits of servos and their architecture?

Ben,

I've been into RC models for some time now and that's a question that is asked quite often, but no one seems to have a definitive answer.

Usually if you are going to extend your servo cables more than a couple of feet it is recommended to use an amplifier to boost the data signal every few feet, especially if you are using high torque servos.
I have run some of my cables up to 5 feet long or so in my larger models, but in this case I use heavier twisted wire to try to keep noise to a minimum.
Allot of the problems come from the current draw of the servo. When a servo is constantly changing direction it creates quite a spike in the power supply lines, which can get back into the data line and cause problems.

If it were me, I would put the controllers out at the displays to keep the servo lengths to a minimum.

Just my two cents...


Robert