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Ready to run wires- how to start?

toolmanmike

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Patron
I got all my avionics, connectors, wire bundles, and tools. I have wiring diagrams and I almost understand what all the components do. Now I’m just staring at it all and I don’t know where to start.
I have a sheet of plywood out ready to lay out wires, don’t know how to begin. How do you lay out the components? Help! I may still be staring at this mess after the avionics are obsolete!
 
Even if you're doing your own wire bundles from scratch, it might be worth your time to call either Stein or Levi at Midwest avionics in Lee's summit and see what they would charge to just do a high level schematic that shows the lengths of all the branches.

I had Levi build my avionics bundles and that was one of the drawings he included with the package.
 
If I man building up wiring harnesses from scratch, I generally start by mounting all the hardware boxes where I want them (making sure I don’t paint myself into a corner by not leaving room for backshells, bend radiuses, etc….). Then I make a sketch of where all the data lines have to go - by that, I mean what box connects to what. Next, I measure - usually with a piece of scrap pitot/static hose. The hose has a nice natural bend radius that makes nice harness loops. Then I put all that information into a more detailed drawing so I know what wires go in and out of bundles to connect to their boxes/sensors/actuators/power sources/etc.

Wiring is truly eating the elephant - you chip away open bite at a time, doing what you can, where you can as you figure it out.

Paul
 
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If I man building up wiring harnesses from scratch, I generally start by mounting all the hardware boxes where I want them (making sure I don’t paint myself into a corner bay not leaving room for backshells, bend radiuses, etc….). Then I make a sketch of where all the data lines have to go - by that, I mean what box connects to what. Next, I measure - usually with a piece of scrap pitot/static hose. The hose has a nice natural bend radius that makes nice harness loops. Then I put all that information into a more detailed drawing so I know what wires go in and out of bundles to connect to their boxes/sensors/actuators/power sources/etc.

Wiring is truly eating the elephant - you chip away open bite at a time, doing what you can, where you can as you figure it out.

Paul

What he said.

I placed all my boxes. Then used schematics and ran every wire needed before attaching the first connector.
 

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If I man building up wiring harnesses from scratch, I generally start by mounting all the hardware boxes where I want them (making sure I don’t paint myself into a corner bay not leaving room for backshells, bend radiuses, etc….). Then I make a sketch of where all the data lines have to go - by that, I mean what box connects to what. Next, I measure - usually with a piece of scrap pitot/static hose. The hose has a nice natural bend radius that makes nice harness loops. Then I put all that information into a more detailed drawing so I know what wires go in and out of bundles to connect to their boxes/sensors/actuators/power sources/etc.

Wiring is truly eating the elephant - you chip away open bite at a time, doing what you can, where you can as you figure it out.

Paul

Thanks for all your constant input. I don’t often comment on your posts but find you always give great info in almost every thread I see.

But a query! Do you put the connectors on in-situ? Do you find any issues with access for crimping pins and heat shrink etc? Or do you do your measuring with the static hose then transfer the drawing to a board for harness fabrication? I worry the first method might lead to poor crimps or unsightly connectors due to access, but the second painting myself into a corner where I can’t get a connector through a bushing or hole etc.
 
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Wiring

Paul pinned the tail on the donkey or elephant.
Manuals, schematics and spreadsheets. Pick one and start
Mount boxes with consideration toward future maintenance.
My build is Dynon with an Advanced Control Module
I mounted boxes that might be touched again on hinged panels. Photo. The Alternator Regulator and ELT Audio buzzer have since been added. The other boxes shouldn't need to be touched so they are on the subpanel.

20230318_160308.jpg
 
Thanks for all your constant input. I don’t often comment on your posts but find you always give great info in almost every thread I see.

But a query! Do you put the connectors on in-situ? Do you find any issues with access for crimping pins and heat shrink etc? Or do you do your measuring with the static hose then transfer the drawing to a board for harness fabrication? I worry the first method might lead to poor crimps or unsightly connectors due to access, but the second painting myself into a corner where I can’t get a connector through a bushing or hole etc.

After measuring, I build as much as I can on the bench - makes for a very clean and easy place to work. You need to keep your mind several steps ahead, however, to make sure that you don’t put pins in connector bodies if they need to go through holes - as you said! In that case, label the wires with connector and PIN numbers so that you can insert them after running the wire. Ideally, you do no crimping or soldering “in situ”…..but eventually, you’ll end up having to do that.

Last thing I do is tie up bundles - I use temporary (cheap) small cable ties in bright colors to temporarily hold wires into bundles until everything is run - then I can do a nice neat job of tieing everything together. Plan on a thousand throw-away cable ties….

Paul
 
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Maintenance

Remember to plan for maintenance. If Box X goes in a location, how will you get to it if it fails.
 
Original poster here, Thanks to all for the advise. This is daunting and outside my normal skill set. What is the benefit of adding large connectors to the panel wiring? Are you making it so the whole panel can be removed for work? I don't think that is practical in my RV-7 because the sub panel is not removable but riveted in and most of my "boxes" will be attached there. I like the hinged panels under the panel. I did incorporate that into my design a long time ago. Now I have to figure out where to put all the boxes!

Other than Transponder and ELT, what boxes are you all mounting somewhere OTHER than behind the panel?
 
Original poster here, Thanks to all for the advise. This is daunting and outside my normal skill set. What is the benefit of adding large connectors to the panel wiring? Are you making it so the whole panel can be removed for work? I don't think that is practical in my RV-7 because the sub panel is not removable but riveted in and most of my "boxes" will be attached there. I like the hinged panels under the panel. I did incorporate that into my design a long time ago. Now I have to figure out where to put all the boxes!

Other than Transponder and ELT, what boxes are you all mounting somewhere OTHER than behind the panel?

Build in the extra wiring so that you can pull the connector after you removed the avionic box off the front panel. Someone has said before, the big hole that fits the modern 10" EFIS will give you great access to the rest of the avionic bay after the EFIS. The only way to know is to try it. We all went through the same headache at first.

I found the wiring and avionics daunting at first but they aren't more difficult than building the airplane. Think of the gratification when you flip the power switch and the EFIS lights up.
 
My best advise is - this is not the time to try and save a few bucks by making the wire runs just long enough. Having extra length available is so much better than being handcuffed by the exact right amount. One consideration is that you want all of your connectors to not be under any strain as that will lead to failures when you start flying. Just enough wire means strain.
 
Original poster here, Thanks to all for the advise. This is daunting and outside my normal skill set. What is the benefit of adding large connectors to the panel wiring? Are you making it so the whole panel can be removed for work? I don't think that is practical in my RV-7 because the sub panel is not removable but riveted in and most of my "boxes" will be attached there. I like the hinged panels under the panel. I did incorporate that into my design a long time ago. Now I have to figure out where to put all the boxes!

Other than Transponder and ELT, what boxes are you all mounting somewhere OTHER than behind the panel?

Yes - make the panel so it can be removed as an assembly. This is the best thing you can do and is easy to achieve.

Stuff mounted to the bulkhead forward of my panel include:
- Alt voltage regulator
- Remote XPDR
- EMS module
- Remote Comm (Dynon)
- ARINC module
- Panel dimmer module
- SkyView network hub

This photo shows where the behind the panel modules are mounted. Note the bare area to the top left. This provided room for the way too deep GTN-650 tray.
A6-EA4839-C7-C6-415-B-AC8-C-7252-B41-B29-B0.jpg


All of these and associated cable runs are easy access once the panel itself is out and on the bench. The panel is connected with D connectors and one large pin Molex for power. Divide the wiring into:
- Wiring between panel avionics (no connectors) and wiring between panel avionics and the rest of the plane (connectors).
- Wiring that stays in the plane when the panel is removed. This includes all the EFIS D connectors, panel mounted module connectors, all switches and breakers (other than the breakers for the panel mounted stuff).

The key on this last part is thoughtful planning on switches and breakers. The photos below show the switches and breakers mounted on the panel “wings” that stay in the RV-8 when the panel comes out. The second is an old shot of the RV-10 (two panel mods ago) with these mounted on the lower panel apron that stay in the plane when the panel comes out.
Side note - a buddy is working an RV-6A backfit and has modified the new panel blank to add a lower apron to do the same.

ECC38590-0-B70-4-D8-B-849-F-214302-AD686-C.jpg


52960066-4140-4345-A8-E1-AB3887950-E21.jpg



The only avionics I have mounted elsewhere are:
- The ADS-B receiver. It is mounted on a bracket aft of the baggage compartment, perhaps a foot away from the ADS-B antenna. It connects to the panel via a single, four #22 conductor shielded cable.
- The two SkyView ADAHRS modules mounted in the tail cone overhead.

All builds will eventually need to do panel work (maintenance and upgrades). Assume you will want to modify the panel after flying for a couple of years. My first build is 20 years old and on its fifth panel upgrade.

The rule, “Never on your back with your head under the panel”.

Carl
 
Locations

Original poster here, Thanks to all for the advise. This is daunting and outside my normal skill set. What is the benefit of adding large connectors to the panel wiring? Are you making it so the whole panel can be removed for work? I don't think that is practical in my RV-7 because the sub panel is not removable but riveted in and most of my "boxes" will be attached there. I like the hinged panels under the panel. I did incorporate that into my design a long time ago. Now I have to figure out where to put all the boxes!

Other than Transponder and ELT, what boxes are you all mounting somewhere OTHER than behind the panel?

Sorry this is long and limited to my expertise.

My transponder, com and adsb are mounted to the sub panel. Advanced Control Module and ELT annunciator are on the starboard hinged panel. Backup EFIS batteries, EMS, Alternator regulator & stall warning circuit board are on the port hinged panel. Panels and associated boxes and cables must clear anything above.

Some manufacturers sell the interconnect cables prewired. Saves a lot of work.

ELT and ADHARS are in the fuse. ELT has a panel. I almost forgot about it. ELT also has an annunciator. Both have batteries to replace at designated intervals. If you have a B&C alternator, there's a regulator box to mount. Access is handy should a voltage adjustment be required.

Make a list of every box. Put sample connectors on each box, one at a time and measure. It's not just the foot print of the box. The connector and cable need space. Consider how you will take that box out if necessary. Orientation of the box matters too when it's time to work on it. There are connectors on ends of cables but usually not many in between. Nuts & bolts or screws & nutplates. The latter are easier but installing nutplates laying under the panel is not fun. Neither is nuts & bolts so pick your poison.

If you have breakers, consider all that wire is carrying power. You need the correct breakers and wire gauge.

How will you pull the panel? Does the controls quadrant come off? It helps to practice and consider what connectors have to be removed to pull the panel.

That's one plus to electronic breaker boxes. Switches are connecting to ground. No power. A harness can be made to disconnect the entire bank of switches. Wire is smaller guage so a d-sub can be used.

Lights need power, switching and some have controller boards.

AP servos, trim servos get connected to the electronics. AP servos probably use a manufacturer's harness. Trim servos can be wired with Ray Allen trim wire. Colors are standardized among many manufacturers.

Flap motor needs to be connected. Power at least. Most builders add a position sensor. The new PH Aviation motor has one built in.

Stick grip controls have a harnes(s). That sort of includes the mic and phono jacks. Tosten grips are pretty well documented. You need to research which pins on the electronics are utilized.

O² may or may not be built in.

CO detection.

Antennas

I can't think of anything else.
 
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Toolmanmike,

I agree w/ everything IronFlight said and would add:

1. Start with the power wiring from your distribution device (breaker/fuse/whatever panel) to each gizmo. I use red & black wire for positive & negative. It is REALLY important to get the polarity correct!! If you get the polarity wrong you WILL damage that $15,000 Garmin GPS Navigator!! So triple & quadruple check that the polarity is correct. (Side note: If you get signal or data pins wrong, it won't work right (and may be a b*tch to trouble-shoot) but you are not likely to hurt anything)

2. Then do the common data busses. In Garmin world everything is interconnected with the CAN bus. In Dynon there's the SkyView Bus (I think.. haven't done a Dynon panel)

3. Then do all the remaining data busses like RS232, ARINC, etc.

4. Finally all the rest of the pin-to-pin wiring.

5. Use some form of documentation to keep track of work as you go. If using a wiring diagram(s) (highly recommend), check-off each wire as you install it. I keep track of the following operations on each wire by marking-up the wiring diagram:
a. route wire into harness
b. label each end
c. terminate each end

6. As others have mentioned - Leave "Service Loops" in everything. Think about how you would access a connector if you have to move a pin from one hole to another. You don't want to be stuck under the panel "hangin-by-your-ankles" trying to reach a connector that is at the end of a wire that is too short. Ideally, you want to be able to work on it while sitting comfortably in the cockpit or on the wing. Keep in mind that if you have a big display in the middle of the panel, you can take it out and you will have a 10 in access hole to work thru.

7. A wire that is a foot too long is waaaay better than one that is an inch too short.

In a complex system, documentation is key. If you spend the time to get the Wiring Diagrams right up-front (and it takes a lot of time) you will be much more successful. You should know where every single wire starts and ends before you start cutting wire.

As others have said, "you eat the elephant one bite at a time". It is technical, tedious, and highly-detailed. (and if you're a real geek, you will actually enjoy it!)
 
PaulD:

1. What is a Nub Duke? Great name. Never heard it before.

2. Instead of hose, I use a old 16/3 orange extension cord w/ the plug cut off.
 
Here is a link to a complete description of the design/build of my RV 10 electrical system.

https://vansairforce.net/community/showthread.php?t=152279&highlight=leok

The wire harness was built on the bench (except the connectors where the wires had to be fished through conduit) and then installed. Very much like a car is built. The wiring diagrams and other documentation files are linked in the thread.

Have fun, take the class noted above. The wiring was one of the most rewarding tasks in my build. 250 hrs with no issues!

Leo
 
Totally agree with IronFlight and others. I started out with a high level interconnect diagram, picture attached (sorry, I know it should be in CAD, but old guy here!), which was built up from the various manufacturer's unit connection diagrams.

Next, I created a spreadsheet of my wiring, which incorporates pretty much all the aspects others have discussed. (click on the black area and a PDF should come up). The spreadsheet started out by detailing the wiring shown in the higher level diagram, giving all runs numbers and wire type info, each end pin numbers, colors, etc., and then as others have pointed out adding route length data by measuring in place with hose or rope. Again, just make sure the wires get cut longer than needed, (Old German saying, "three times cut off and still too short".), then trim as they are bundled to each destination and trial routed to final positions. Method of pinning and connectorization have already been well discussed. I did all mine in place, but agree you get a neater job on the bench.

Lastly, the spreadsheet and high level diagram are highly useful tools to keep up to date as your plane may evolve in the future.

Reinhard Metz
 

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