Trio servos and shielded wire question.

Merry Christmas everyone,


I have an AP servo wiring question.
The Trio and MGL docs for the Gold standard servo have you running a 4-conductor shielded wire. My pitch servo looks to have about a 12' run, but the wing servo will have about a 14' run. For power, it looks like I'll need 18awg wire, but I can't seem to find 4-conductor shielded cable anywhere. 20awg is the largest I can find.

Is it OK to use single 18AWG wires for power and a 3-conductor 22AWG shielded cable for data?

Does anybody have a source for 18AWG 4-conductor shielded cable?

thanks,
-John

Hi John

If you check out this PDF you will see that the 4 core wire and power wires used by MGL are 22AWG. I have just checked my load planning chart and Trio gave me in an email a load value of 1A and a protection rating of 5A.

The electrical wire selection charts I have seen only go up to 20AWG but if you look at the 1A line and extrapolate (not unreasonable I think) then the run x 2 (there and back) looks fine for continuous (30 - 35 ft) and plenty for intermittent (60 to 70 ft).

If you look at the Pro Pilot Manual (the system uses the Gold Servos) on page 80 the shielded wire is 22AWG 4 Core as well.

Hope this helps?

Bob
www.rv-8.co.uk

Bob,

Thanks, this is exactly what I needed to know. I'll go over the MGL and trio docs again.

cheers,
-John

John Courte said:

Bob,

Thanks, this is exactly what I needed to know. I'll go over the MGL and trio docs again.

cheers,
-John

Click to expand...

The wiring is generally uncritical but the data lines at least should be shielded. Make sure that the shield is connected only on one side so it does not conduct any currents (which could result in the shield itself radiating).

The only critical issue is that we would like to see a 33 ohm resistor placed in line from the servo's ground to the MGL COM Extender with a seperate ground connection between the servo and the supply ground.
This prevents possibly high groundcurrents from flowing through the COM extender and EFIS in case of a ground fault.

Rainier
CEO MGL Avionics