Using a phone cord for a servo cable extension?

Jed

I need about 60" of servo extension and I'm having a hard time finding an official servo cable extension at that length. So my thought is to use phone cord instead, or maybe a pari of speaker wires? Is there any drawbacks to this? Will it work ok or are the wires in a phone cord too thin? What types of extension is possible, as far as what do you think my length limit would be?

tpw_man

I have no idea what the length limit would be, but a telephone cable might not work so good if you are carrying the power along it. If you are just dealing with signal, and if you can get the proper connectors, I think a telephone cable would work fine.

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I am 1010, so be surprised!

Beau Schwabe

I've used CAT5 CAT3 cable over 30 feet... your going to need a cap 470uF near the servo power, and a 4.7K resistor in series with the signal close to the Stamp.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 2/13/2008 5:06:15 PM GMT

Oper8r Al

Check your local hobby shop for servo wire. I know hobbytown USA by me has 12' for around 5 bucks. If you want to get it online try this link http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN661&P=7. They also have·both male and female ends for the·wire.

Hope this helps

Al

Jed

Thanks for the info. Actually the 60" length will be going to a Ping))) unit, and 24" wil be going to a servo. So regardless of whether I go with CAT5 or actual servo wire I will still need the capacitor and the resistor on the 60" length correct? Is the 24" length ok without that? Are those to keep spikes picked up by the cables down? Do I put them both on the stamp end on the servo/ping circuits?

terry_bear

Beau.

When you used Cat5 for your long servo run, did you use 4 wires (2 gnd , 1 power, 1 signal) or 3 wires? The two gnds would be tied together at both ends...

Terry

Phil Pilgrim (PhiPi)

Actually, it would be much better to use separate supplies for the servo and for the electronics and keep the two grounds separate, joining them only at the servo end. That way, none of the servo's motor current would be returning on the signal ground lead. Also, if you use RJ12 (6-conductor phone wire), you could double up on the motor supply leads.

-Phil

terry_bear

Phil

Yes, that makes sense. Should have considered it...

Beau Schwabe

terry_bear,
·
Actually I was mistaken; it was a 6-conductor CAT3 cable that I used.· CAT3 is defined as UTP (Unshielded Twisted Pair) cable designed to carry voice and·data up to 10 Mbps.
The particular cable that I used was 24AWG.
·
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Reference Thread:
http://forums.parallax.com/showthread.php?p=549166
·
1 - GND
2 - PWR
3 - Servo1 signal
4 - Servo2 signal
5 - Laser Power
6 - Not Used
·
·
Jed,
·
For the 5ft (60 inches), and 2ft (24 inches) the capacitor is probably not as necessary.
With long runs (30feet) you start to experience IR drop.· To compensate for this,·a local bypass capacitor located in close proximity to the Servos, will usually do the trick.
A series resistor is a good idea, to help attenuate any noise that might be picked up over the wire due to·any antenna effects, or noise from the servo entering the signal line.
·



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Beau Schwabe

IC Layout Engineer
Parallax, Inc.