Dynon Servo Twisted Pair Wiring Question

[pazmanyflyer]

Originally Posted by Jrskygod

Can we get a picture and info on the hub please.

Picture:


VAF thread:
http://www.vansairforce.com/communit...ight=dynon+hub

[PhatRV]

Originally Posted by pazmanyflyer

Picture:


VAF thread:
http://www.vansairforce.com/communit...ight=dynon+hub

Wow nice looking hub. I will consider getting this by the time I start building my panel.

[PNLBLDR]

Here is the wire used in the Dynon cables, which can be bought already twisted...


https://www.steinair.com/product/22-...-twisted-wire/


https://www.steinair.com/product/22-...-twisted-wire/

[RVDan]

Originally Posted by Bill Boyd

What happens if you don't twist the wires?

This question has real-world ramifications for this boy who pulled multi-conductor wire early in the project and just now realized Dynon wants some twists in the cabling.

The twisted cables are all for data lines with high level signals. The twisting prevents noise from being generated by the wiring. The wires, if not twisted will put out electromagnetic noise that could affect other systems, in particular audio quality. Twisting is highly recommended. Shielding would be required to prevent to prevent the databus from being affected by the indirect effects of lightning inductive coupling) or HIRF (high energy radiated fields) from things like microwave antennas and certain high energy radar emissions.
Twisting the high and low wire causes the fields to be neutralized. If you are wired up and no issues, good for you. It just means that your wire routing separated the noise from potential victim systems, either by design or luck.
Theoretically, without twisting, you could cross couple the EMI into other data lines, particularly if they ran parallel for some distance.

The noise could also couple into antenna cables causing problems.
Again though, if your wiring is completed, and no issues don?t rip it out to twist the wire.

[Bill Boyd]

My wiring is far from complete, but the runs to the trim and A/P servos are already pulled in the wings and fuse. Not going to change the trim servo cables because they are not likely emitters or victims of RFI, but the autopilot servos are a completely different beast, signal wise. I'm a bit reluctant to test this and have to re-pull wire at the start of Phase One, but also reluctant to believe it's going to make a real-world difference in system behavior.

[Robski]

When it comes to avionics why do people presume to know better than the manufacturer?

If it says use twisted pair then just use it and save brain-power and brownie-points for when there are real problems.

The number of issues I have helped with where the installer has said “I read that but I didn't think it was important“...

[N804RV]

This is one example of why buying the Dynon pre-made wire bundle/cable is worth it.

https://sites.google.com/site/markgu...%20other%20out!

[vlittle]

Originally Posted by lr172

I grew up in the telephone business. They learned well over 50 years ago, that without twisting the pairs that are in close proximity that one audio conversation would bleed into the other due to the magnetic radiation from the electrical signal. The same effect occurs in data transmission and twisted pairs are typically spec'ed to eliminate this bleed over and the errors that come with them. The faster the oscillation of the binary data signal, the greater the chance of error. Slower speeds, like RS-232 have very few problems with this bleed over. 100 Megabit LAN cables have lots. CAT 5 cable has as much or more to do with the capacitance of the insulators as it does with the twisting, to deal with the same issue.

Cables that aren't in a tight bundle, like a multi-pair cable, have significantly fewer issues, as do short cable runs. The Dynon DSAB uses an RS-485 transport. You can do some research on the issues to be expected without using the 485's required twisted pair. RS-485 resembles a CAN bus at the physical layer.

Others should know that most aviation wire is not twisted pair. All of the wires in the bundle are twisted together and not in pairs. a typical mil spec four conductor cable should never be used for two pairs when twisted pairs are specified.

Larry

Just in case too much information is required, telephone cables also have what is called 'roll' so that bundles of 25 twisted pairs do not run in parallel with each other for long distances. This reduces noise between adjacent pairs. Twist and Roll, sounds like a 60's dance. Not a shield in sight.

V

[Robski]

Originally Posted by N804RV

This is one example of why buying the Dynon pre-made wire bundle/cable is worth it.

That and the fact the pre-made thermocouples harness is cheaper than making it yourself!