Servo extentions - RC Groups
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Apr 10, 2013, 02:39 AM
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Servo extentions

Hi, I'm building a plane and mounting the aileron servos out in the wing. I need to put in some extension wires, but want to put my mind at ease about something...

Do the extension wires cause any problem for the servo operation? I'll be using the standard servo wire plus two extensions per servo.

Any issues here?
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Apr 10, 2013, 03:12 AM
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The main potential issues are too-thin wire and too many connectors causing too much electrical resistance.

My preference is to solder an extension lead on, using "heavy duty" servo wire, so that I still have only one connector per servo. In fact, with one-piece wings I solder my opposite servo leads together to make a Y, so that I only have one connector for the two servos.

If you must use pre-made extension leads, try to get ones that are long enough, rather than connecting two together to make up the length. And for the connectors that will be buried in the wing, tie a piece of dental floss around them so they can't come apart.
Apr 10, 2013, 04:20 AM
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The voltage issues you mentioned are along the lines of what I am concerned with... How difficult is it to solder the ends on custom made leads? I solder like I weld... Not beautiful but it works haha
Apr 10, 2013, 07:19 AM
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I can't weld, so you're ahead of me

Anyway, soldering servo leads is simple so long as you have the right equipment -- a decent iron, some resin-cored solder, and a "helping hand" device (or some home-made jig) to hold the wires in position while soldering.

I strip about 1/4" of each wire end, twist them so they're neat and tidy with no little bits sticking out, and then tin them with solder. Then I lay the two tinned ends side by side, facing each other, and a quick dab (maybe two seconds) with the iron with a little bit of solder on the bit, and the job's done. Look carefully and you'll see the two wires sort of melt into each other when it's done correctly.

Don't forget to slide a bit of heat-shrink onto one side before you solder the joint, then slide it over the joint when it's cooled down, and shrink.

You can solder the cut-off end of the wire, with the plug attached, onto the other end of your extension lead, or you can crimp on a new servo plug (one solder joint less) and discard the old one.
Apr 10, 2013, 01:25 PM
Hope to get out of life alive
kenh3497's Avatar
If you use connectors in the wings I like a dab of dielectric grease in the connector to help prevent corrosion or at least slow it down.

Apr 10, 2013, 03:23 PM
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earlwb's Avatar
If you don't want to cut connector ends off and solder, etc. You can use the extensions as is, but what I do is use some string, or twine and tie the connectors so that they don't unplug later. There are gaps between the3 wires making it easy to thread the string through so you can tie them together so they don't accidentally come unplugged on you later.
Apr 10, 2013, 03:53 PM
Illegitimi non carborundum
grosbeak's Avatar
Where connections are necessary (batteries, detachable wings, etc) I use plastic retaining clips. With extensions, I solder. I wrote a tutorial on the subject - it's on my website if anyone's interested:
Apr 11, 2013, 06:20 PM
Registered User
Thank you for all the replies! I feel much better about it now. I didn't think about snipping the plug ends off and soldering the wires together inside the wing.
Apr 11, 2013, 06:20 PM
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And thanks for the link Grosbeck
Apr 11, 2013, 06:22 PM
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I have heard that if you have really long extensions (2 feet or better) tie a simple overhand knot in the wire as a substistute for chokes. Of course, if you DON'T tie a knot, you may not need a 24" extension......

Apr 11, 2013, 11:08 PM
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Hi, what do you mean by chokes in the wire?
Apr 12, 2013, 10:44 AM
Registered User
The only time that chokes (or twisted lines) would help is if the source of any adverse signals were generated in the servos and that would minimise any feedback from the servo into the receiver. There is no need for such devices in most (if not all) servo installations. All extrainious signals (if such signals exist) picked up by the leads to the servo will be "common mode" and will not effect the servo performance.
Apr 13, 2013, 04:18 PM
Suspended Account

For reliability

I suggest that only one connector be used at the receiver and any servo extensions be soldered.

Apr 14, 2013, 02:46 AM
Registered User
Originally Posted by sawitup
Hi, what do you mean by chokes in the wire?
A choke is that little ferrite ring that you sometimes see the wires wrapped around on an ESC or stand-alone BEC. It allows dc current to flow as if it were just the wire, but it provides an impedence (I think that's the term) that limits how much ac current can flow through. That reduces the chance of interference getting through to the receiver, though I've never found it necessary on servo leads, nor indeed on any leads, when using 2.4GHz. I used them on ESC and BEC leads when I was on 35MHz.
Apr 14, 2013, 11:18 AM
Registered User
I sometimes use shrink material, slip over the connections and use a heat gun to shrink the material. About the same as using plastic retainers and whole lot easier than tying knots. I also use as a minimum 6v (five cell) receiver batteries. No brown out and helps with the potential voltage drop across the connectors. I also solder in extended wires, I cut the servo lead in half and add what I need. I also use shrink spaghetti on those solder jobs.

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