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Servo Extension Length

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Old 12-06-2004, 01:19 AM
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Andy540T
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Default Servo Extension Length

How long of an extension cable can you use before needing a "choke" on the line?
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Old 12-06-2004, 05:49 AM
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Geistware
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Default RE: Servo Extension Length

I would just twist it a little and never worry about a choke.
ORIGINAL: Andy540T

How long of an extension cable can you use before needing a "choke" on the line?
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Old 12-06-2004, 04:32 PM
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Default RE: Servo Extension Length

Despite the common practice twisting the servo's lines does little to reduce interference unless you have an absurdly over sensative receiver with bad filters. Take a hint from electronics companies. Anything with cable over about 3 feet in length has a ferrite bead somewhere on it, keyboards, mice, and most monitors. I'd also put chokes on anything that was about the length of an antenna wire.
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Old 12-06-2004, 04:44 PM
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Default RE: Servo Extension Length

I've never found a need for a choke in a servo lead, they are more apt to cause problems than to correct any.
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Old 12-07-2004, 10:12 AM
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Default RE: Servo Extension Length

ORIGINAL: Lynx

Despite the common practice twisting the servo's lines does little to reduce interference unless you have an absurdly over sensative receiver with bad filters. Take a hint from electronics companies. Anything with cable over about 3 feet in length has a ferrite bead somewhere on it, keyboards, mice, and most monitors. I'd also put chokes on anything that was about the length of an antenna wire.
Keyboard, mice and monitors have much more complex and sensitive circuits than we have. Get an interface book and take a look at what happens when you press a letter on the keyboard. You will be surprised how complex it is. I often wonder how it works at all.
Our circuits have at best one or two pulses running parallel. Even if cross coupling occurs the impedance is so low I doubt you will notice anything.
With digital servos, strong current surges could couple but a little twisting of the wires should cancel that out. Just don't twist them all the same direction.
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Old 12-07-2004, 12:56 PM
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Default RE: Servo Extension Length

Ferrite chokes are best used to cure a known problem by experimental application. I would say try it without the chokes first. Chokes can cause problems as well as fix them.
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