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  #1  
Old 06-01-2021, 01:42 PM
CJK CJK is offline
 
Join Date: Mar 2009
Location: Middle TN
Posts: 126
Question Wire Choice?

I'm still quite early in my build, but not too far down the road is installation of the elevator trim servo and the tail strobe/position light. I've read several threads here where folks talk about using different wiring from that supplied with the kit (and don't worry, I'm definitely using different connectors!), but I've grown increasingly confused as to what to choose as a replacement.

Can anyone make some recommendations -- with explanations, please! -- as to the best wire/cable to use for these two applications?
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Chris Klugewicz
fly from KJWN, live near KSRB

RV-14 build underway
∙ N415EJ reserved
∙ empennage started April 2021
∙ currently working on: Section 6 - Vertical Stabilizer

build log: kitsune.aero
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  #2  
Old 06-01-2021, 02:13 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,276
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You want durable, flexible and easy to install.
- Elevator trim: Single four #22 conductor shielded wire. Two conductors to power the trim motor, one for servo position voltage, one for servo position sense, shield for ground.
- Tail nav/strobe (assuming you are using LED): Single three conductor #20 shielded wire. One conductor for nav power, one for strobe power, one for strobe sync, shield for common ground.

These shielded cables are available from Stein.

Carl
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  #3  
Old 06-01-2021, 04:59 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 360
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Quote:
Originally Posted by Carl Froehlich View Post
You want durable, flexible and easy to install.
- Elevator trim: Single four #22 conductor shielded wire. Two conductors to power the trim motor, one for servo position voltage, one for servo position sense, shield for ground.
- Tail nav/strobe (assuming you are using LED): Single three conductor #20 shielded wire. One conductor for nav power, one for strobe power, one for strobe sync, shield for common ground.

These shielded cables are available from Stein.

Carl
Is it normal to use the shield like this to actually carry power?

I used this for my trim even though itís not shielded - hope I donít regret that later, if I end up with a Garmin servo. https://www.steinair.com/product/24-...wire-jacketed/
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  #4  
Old 06-01-2021, 05:04 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
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Location: Dogwood Airpark (VA42)
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Quote:
Originally Posted by TASEsq View Post
Is it normal to use the shield like this to actually carry power?
SNIP
Yes.

Carl
Plus extra characters.
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  #5  
Old 06-01-2021, 05:29 PM
DRMA DRMA is offline
 
Join Date: Jan 2016
Location: Sugar Land, TX
Posts: 503
Default Cable Shields As Power Wires

Quote:
Originally Posted by TASEsq View Post
Is it normal to use the shield like this to actually carry power?
While you may be able to get away with using the shield as the return leg (ground) for the nav/strobe lights, I wouldn't recommend it. The shield is meant in most cases to prevent the transmission of EMI/RFI between cables and other sensitive devices.

When powering a pulsing power device such as a strobe, the EMI/RFI is typically higher and can cause interference with other devices in your aircraft such as radio reception and other sensitive low voltage electronics such as magnetometers.

On my aircraft I carried a separate return/ground conductor back to the ground block inside of the shield, and terminated the shield separately. Upon completion of my RV-10 avionics systems, I had zero noise or interference issues.

While this adds a little bit to the cost of the cable, and requires additional terminations, it is in my opinion a preferred method. As a registered professional electrical engineer with a degree in electronics engineering and significant experience in industrial control system design and construction, that would be my recommendation. But as the builder, it is of course your decision.

Regards,
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  #6  
Old 06-01-2021, 05:53 PM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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If you are going Garmin it's recommended that you use a 2 cond/shielded (22ga) wire from the servo to the trim motor, Garmin uses PWM from the servo to control trim motor speed and therefore is subject to emitting noise.
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
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  #7  
Old 06-02-2021, 04:42 AM
CJK CJK is offline
 
Join Date: Mar 2009
Location: Middle TN
Posts: 126
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Thanks, guys -- very helpful info!

Based on the recommendations above, I'll likely run a 20-4 cable for the tail strobe/position light. (And yes, it's an LED: AeroLEDs SunTail.)

I'm a little confused about the wiring of the elevator trim motor, though. I'm definitely going with a Garmin panel and AP servos, so I'll need to run the 2 conductor cable Walt mentioned from the pitch servo to the trim motor. But do I ALSO need to run the 22-4 cable that Carl described? Or does the connection from the Garmin servo replace the 2 power conductors to the servo?
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Chris Klugewicz
fly from KJWN, live near KSRB

RV-14 build underway
∙ N415EJ reserved
∙ empennage started April 2021
∙ currently working on: Section 6 - Vertical Stabilizer

build log: kitsune.aero
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  #8  
Old 06-02-2021, 05:22 AM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 360
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Quote:
Originally Posted by CJK View Post
Thanks, guys -- very helpful info!

Based on the recommendations above, I'll likely run a 20-4 cable for the tail strobe/position light. (And yes, it's an LED: AeroLEDs SunTail.)

I'm a little confused about the wiring of the elevator trim motor, though. I'm definitely going with a Garmin panel and AP servos, so I'll need to run the 2 conductor cable Walt mentioned from the pitch servo to the trim motor. But do I ALSO need to run the 22-4 cable that Carl described? Or does the connection from the Garmin servo replace the 2 power conductors to the servo?
If I were running my tail wires again (I just might!) then I would run a shielded 2 core 22awg for power and a 3 conductor jacketed for the trim position. For a couple of reasons - one is to shield the power wires, but the other is they end up going to 2 different boxes in the end so would be better as seperate cables. As it stands for me now, where my 5 conductor goes past the Garmin servo I will need to break the 2 power wires and route them to and from the servo. Then the length of wire from the servo to the trim servo is unshielded - but that’s the way the factory harness runs so I’m hoping it’s fine.
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http://www.tasrv14.blogspot.com.au/

Last edited by TASEsq : 06-02-2021 at 05:34 AM.
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  #9  
Old 06-02-2021, 07:12 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by TASEsq View Post
If I were running my tail wires again (I just might!) then I would run a shielded 2 core 22awg for power and a 3 conductor jacketed for the trim position. For a couple of reasons - one is to shield the power wires, but the other is they end up going to 2 different boxes in the end so would be better as seperate cables. As it stands for me now, where my 5 conductor goes past the Garmin servo I will need to break the 2 power wires and route them to and from the servo. Then the length of wire from the servo to the trim servo is unshielded - but that’s the way the factory harness runs so I’m hoping it’s fine.
As Trent above mentions, a 3 wire to the GEA24 from the Ray Allen servo for position. and a separate shielded 2 cond from Garmin servo to trim motor.
Std 22 single conductor from trim relays to Garmin servo trim input.

Follow the recommended light wiring for nav/str.

I'm doing a wiring job on a 14/Garmin, not using any of Van's harnesses.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 06-02-2021 at 07:17 AM.
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  #10  
Old 06-02-2021, 08:43 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
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Default ...and

"... As a registered professional electrical engineer with a degree in electronics engineering and significant experience in industrial control system design and construction, that would be my recommendation. But as the builder, it is of course your decision..."

You may want to let AeroLEDs in on it because their installation instruction specify using the shield.

I wired my RV-10 per their recommendations and I have no avionics noise whatsoever...
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