Long Servo leads

[N726AC]

Do your current servo leads leave you feeling inadequate? Want just a little more? TBM has a solution. Ready made long, heavy duty servo extensions. Sold by the pair, available in 6",12",18",24",36",48",60"and 72 inch lengths. Gone are the days of making up your own long servo extensions, no more tiny little pins and fussy crimpers, no more two male ends (or female).No need to piece multiple extensions to get the proper length
Made from heavy gauge, twisted wire, these extensions have JR male ends and Futaba female ends so that either JR of Futaba extensions or servos can be connected without problem.
http://troybuiltmodels.com/ServoExt.htm
941-342-8685

[Tired Old Man]

What's the voltage line drop on leads over 4' long? I recently did some experimenting and found that even with the better wires extensions longer than 4' have a significant line drop. Enough where with a 6.5v input voltage the output at the opposite end would be well below 6 volts. Adding a connector in that length makes the drop even worse.

[N726AC]

	Quote: Originally Posted by Tired Old Man
	What's the voltage line drop on leads over 4' long? I recently did some experimenting and found that even with the better wires extensions longer than 4' have a significant line drop. Enough where with a 6.5v input voltage the output at the opposite end would be well below 6 volts. Adding a connector in that length makes the drop even worse.

Direct from TBM website,

TBM conducted its own servo extension testing using the equipment shown. We found that adding a single servo extension (22 gauge with universal connectors) between the Rx and the servo will cost you 1.5% - 5% of your power to that one servo. Adding another extension will cost you another 1.5% - 5% and so on. In one of the many tests run, I put ten 6"extensions in series and measured a total drop of 15% of the maximum torque that a single JR-8711 could put out. In another test, I put ten 48" extensions in series (40' of extensions) and found the drop in power to be 55%. Therefore losses due to servo extensions is a combination of plug losses and wire resistance losses.
POWER LOSSES IN SERVO EXTENSIONS

SERVO EXTENSION LENGTHEXPECTED TORQUE LOSS 6"1.5% 12"2% 18"2.5% 24"3% 36"4% 48"5%

WHAT'S THE BOTTOM LINE OF THE ABOVE TESTING?:
* With proper servo sizing, you will not experience any difficulties using extensions.
* Never use extensions between the battery and the Rx. If you need more length, splice in additional 18 gauge wire.
* Use the shortest length extensions possible.
* Use one long extension instead of 2 or more shorter ones.

[BTerry]

I am not as worried about the voltage drop in the DC circuit (power), but I am very concerned about voltage drop in the signal wire (0/5V/0 square wave, very low current). I wonder if anybody has checked that?

I remember a few years ago people were having Hitec servos stop reacting when using Futaba receivers, and it was in part due to voltage drop on the signal lead, exacerbated because Futaba apparently used a lower voltage signal than the Hitec servo was designed to use. This was probably 7 years ago...

[Tired Old Man]

The line loss you are concerned about is a subject some aviation oriented electrical engineers and I were discussing about a week ago. The line loss is equal for the entire wire group and not limited to power or signal. Beyond 4' in length you need to be pumping more voltage to maintain a 6v constant. We left plugs out of the equation since they are a known factor in line drop. They can significantly reduce the end voltage all by themselves, and eliminating plugs via splicing is the way to go. One of the items factored into the discussion was the ability of a 22 ga. wire length to be able to maintain a 2 1/2 amp constant at the working end. That was to allow for a "stalled" current load. Beyond 4' it won't happen without a higher input voltage, so the servo output will fall off. Like 7 volts or better, so a system that incorporates adjustable voltage can make the day.