HDX Display Power Input Question

badia358

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The Display D37 connector has two Power Input pins (1 & 20). I was planning to connect one power pin (1) to the VPX and the other pin (20) to a backup Power Bus that I would manually switch to if there are any issues with the VPX. My question is if this is the best way to supply power to the HDX Display? Plus will a single power input pin handle the current requirements for the HDX display and other subsystems that get power from the HDX display?

Thank you...
 

John Bright

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The SkyView Display power inputs are not diode OR'd. There are two power inputs, and also two ground connections, because the D connector pins individually are not rated for the current. This is common practice across manufacturers.

Ref the SkyView System Installation Guide, "to reduce current loading in each wire — these are not for redundancy and both must be connected to the same power source"
 
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JurgenRoeland

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I'm quite new to all electrical component wiring and to the point to connect the skyview hdx to the vpx 12-9. I also read the remark in the manual on D37 saying "There are two unterminated solid red primary power input wires (to reduce current loading in each wire—these are not for redundancy and both must be connected to the same power source) and two unterminated solid black primary ground wires."

How do you get these 2 wires together in the vpx ? Do you use a butt splice connector just in front of the vpx power pin 12-9 and feed a single wire in the power pin or should I crimp both wires together in the vpx power pin if that's physically possible ? As they are talking about power distribution I assume the splicing is not a wise decision as it's brought back to a single wire feeding into the vpx.

Sorry for the probably very stupid question but I'm very new to all this. I have the VPX-PRO
 

Rhino

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The Skyview has two pins (1 and 20) for those two wires (there's two ground wires too) because a single wire isn't enough to handle the current That's at least partly because several other units in the system (ADAHRS, EMS and ARINC modules) get power from the Skyview. According to the manual, VP-X gives you two options, route power through the VP-X to the Skyview display (for protection), or simply use the VP-X to monitor the power going to the Skyview (protected by a standard breaker). If you choose the first route, the two power wires going to the Skyview must be soldered together to a single pin on the VP-X (page 36 and 37 of the VP-X install manual). The diagram shows them spliced at the Skyview end, but I'd do it at the VP-X end to minimize the length of the single wire. I'd put the solder joint in a good quality, closed end crimp splice connector, such as one of these:
https://www.digikey.com/en/products/filter/terminals/wire-splice-connectors/305 (I'm partial to AMP connectors).
Make absolutely sure there's good strain relief. Just be aware that you're now routing power to the Skyview over a single wire, which Dynon says may not be enough. Obviously it's your choice, but I wouldn't do that. I'd route power to the Skyview independently, and just let the VP-X monitor it.
 
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JurgenRoeland

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thanks for the answer. I agree on your view on splicing them on the VPX end rather than like in the displayed image in the vpx manual. The link showed 30000 results. I assume you are referring to solder sleeve applications for bringing them together. I have these from steinair in 3 dimensions. (https://www.steinair.com/product/18-solder-sleeve/) if I understood well, you strip a bit of the insulation near the end, put solder sleeve on, make the second wire bit shorter and strip at the end and solder both to have one of the two wires to continue into the power pin.
 

Rhino

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Sorry. Wrong link. Something more like this:
It's more along the lines of protecting the connection, rather than providing the connection, like a solder sleeve does. You can use a solder sleeve, but with two wires on one end and one on the other, finding the right size might be difficult. Solder sleeves don't always provide the best connection for higher current, though we aren't talking a whole lot here. That's just my personal preference.
 

John Bright

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Bottom line:

The wires are not the current limiting factor, it's the D connector's pins. Could be conservative from a current standpoint when Dynon uses two pins for power and ground to Skyview Display but no second-guessing the Dynon install manual.


From a voltage drop standpoint the second wire is needed to meet AC 43.13-1B.

==============================================

Some details:

The red and black power wires in the SV-HARNESS-D37 are 22 awg, specifically M22759/16-22. 22 awg is conventionally good for 5A based on 10C temperature rise not in a bundle.

D connector pin/sockets are nominally good for 5A unless they are heated by nearby current-carrying pins which could be somewhat of a consideration because all four subject pins are adjacent on another in this case, 1, 20, 21, and 22. There may also be considerations for the foil on the circuit board or other aspects inside Skyview display.

Per the install manual, Skyview display draws 2.4A. Add items powered over Skyview network like GPS puck, ADAHRS, AP panel, EMS, ARINC, knob panel, SV Bat, USB video, USB WiFi and you could conceivably be up to 4-1/2 A.

As for voltage drop, suppose the harness is 5 feet long, round trip of power and ground is 10'. With two 22 awg wires the voltage drop is 0.36 V which is under the 0.5 V recommendation in AC 43.13-1B.

  • 16.1 Ohms per 1,000 ft, 10 feet, 4-1/2 A gives 0.72 V. Parallel the second conductor and it's 0.36 V.
 

Rhino

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The VP-X specifies 20 AWG for their power pin to the EFIS, so that should give you 11 amps total capacity. Tying that to the two 22 AWG wires in the Dynon harness should work just fine. As John hinted at, Dynon has said there are considerations for the internal boards/components in the Skyview that necessitate their two wire power standard, in addition to possible connector limitations. I suspect it's more the former rather than the latter. The lap splice link from Bob Nuckols is technically a lash splice (wrapped strand). You can do that with heat shrink, but it would need to be dual wall heat shrink, and should be secured at both ends (AC 43.13-1B, Section 13). That's why I would opt for the pre-made splice, at least in this instance. Too many pre-made splices adds bulk and weight to your install, so you don't want to use them a lot, as Bob noted. But in this instance, I would, particularly when you consider the crimp isn't the actual connection. The solder joint is.
 
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jakej

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Come on guys, you’re making a mountain out of a mole hill, it’s much easier to use what you’ve got to work with without soldering 😉.
The 2 twisted wires (22 awg) easily fit into the VPX pins (some circuits go to 15amps) as they are suitable for up to 16 awg - NO soldering required & you have a neater job without solder sleeves.
 

Rhino

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Thanks, Jake. I'm not familiar with the VP-X pins.
 

JurgenRoeland

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thanks everybody for all the contributions. I feel like I learned a lot today. Will give it a try if I can get both insulations and wires in the vpx pins, otherwise, I'll go with Rhino and Johns clear answers on splicing.
 
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