AeroLEDs Grounding... Am I over thinking this?
 

I'm starting to install my new AeroLED Nav/Strobes on my not yet closed QB wings and wanted to see if I'm being too anal about grounding. For the grounds at the lights, the installation manual states to ground the 3 conductor cable shielding, the black wire from the light (NS 90) and the case of the light itself. (See 1st image below)

So I'm wondering if I need to make a separate line from each ground to the airframe? (see 1st drawing in 2nd image)

Or can I pig tail the shield to a pin on the cable side molex connector, have that pin mate to a pin on the light side connector that ties the case ground to the black wire, then to airframe ground? (see 2nd drawing in 2nd image)

Or even tie the light's case to the light's black wire to the light side molex connector pin and connect the cable side pin to the shield and to airframe ground.

AeroLEDs wiring diagram:


My ideas. The 1st one is tying the grounds together and then going to airframe, the second is taking each ground to airframe.


Thanks!
Russ

Local
 

I don't have Aeroled's but I locally grounded all of my lights without any problems. I had Aeroflash Position and Strobes and Duckworks landing lights. I locally grounded at the tip rib and everything was fine and electrically silent.

I retrofitted Aveo lights using the same wiring with local grounds. Works perfect.

I know there were some noise issues with AeroLeds and that may be why there is a little extra. Call Dean and see what he says. Great guy!!

I interpreted this a bit differently. The way I read their diagram, your 1st drawing is almost right. I would say is there is no reason to ground the black wire that is in the bundle ("to switches" in your diagram). If there is a black wire in your bundle, it would remain free and not connected to anything. So ground the black locally off the light, ground the light casing and you're good to go.

Lemmingman... I shouldn't have labeled that wire going to switches 'black'. It's just a pigtail connected to the cable shielding.

Do not take it back to the airframe...
 

The SHORT length ground back to the case is to return radiated noise energy back to the light and not to your radios and intercom. Dean from Aeroleds told me that they would be incorporating this return ground internally in the future.

First drawing
 

I think your first drawing looks right. The wiring diagram from Aeroled is simple and correct, you just need to stare at it awhile.

I think I had three grounds per side, locally at the light. One shield, one from the light wiring and a third from the light mount screw.

Remember to grind the anodizing off the aluminum housing or you'll find a continuity test will show no continuity.

I am trying to figure this out as well.
 

Stephen, are you saying the 1st sketch is incorrect? I was planning to do it this way but I am putting the black wire from the light through the connector then to local ground for easy removal of the light.

The aeroled diagram shows connecting the shield to ground back at the source (VP-X in my case). Is this correct? Isn't there some guidance to only connect sheilds at one end?

That's what I did.

I have Aeroleds and I believe their website has information about grounding and installation that may be of help to you.

Russ,

Be careful with these units to follow the instructions. A number of people I am aware of (including me) have had problems.

My experience is that if you follow the instructions they should not break squelch, however the Nav lights are noisy and emit RF that can interfere with your COM and/or degrade your receive range.

I would recommend keeping the local case grounds as short as you possibly can. Perhaps riveting to the nearest nutplate on your wingtips, rather than a long pigtail to enable removal of the tip. At the rudder, I would try to attach the ground to the bottom of the rudder itself, rather than running back to the fuselage.

I'm still working through the issues with mine and it may well be an error on my part but they are currently not as good as my Whelen System #7 was. It is possible many owners are not aware of any decrease in performance as they do not use the lights often, do not have a "clean" baseline to compare to or have not tested receive sensitivity with the lights on/off.

Regards

Richard

If you know Chad and Glen down there at YSBK......they would love to learn from your experiences too, they have the same drama even when they believe they followed the instructions.

Hmmmm Whelan's do work nicely :)

Yes David, We have 3 RV's at YSBK with the same problem. Two have been installed exactly as per the instructions (as best as we can determine). The other has not been and is (understandably) worse.

The Whelens do work well until the power supply for the strobe fails and they want $600 for a new one.

I am going to follow this through with Aeroleds. My personal view at the moment is that my current installation is far from optimal for NVFR/IFR ops.

Cheers

My aeroleds have worked perfectly with no issues.

Closely follow the Aeroled directions...
 

The most critical issue with these lights in reducing emitted noise into the radios and intercom is returning the ground to the case with a short run... this makes a BIG difference. I used a handheld radio to evaluate the noise from the strobes and position lights and the difference is quite remarkable.

Here is a shot of the wingtip connection for reference.

Stephen, where did you ground the shields on each end?

Shields
 

Firewall and outboard rib.

Lots of ideas here. I'll see if I can get AeroLEDs to weigh in. :-)

Im assuming I'm not the "other":o as I'm very sure I've followed the instructions to the letter, including the extensive details on the Aeroleds site. Still, COM frequencies around 120 break squelch - which makes YSCN problematic! Let me know if you come up with anything!

Cheers

These problems and they cost HOW MUCH? Mercy....

hahahhahah :D

Chad and Glen probably assume they are not the other....how many are there?

Glen tells me he followed the instructions carefully, of course EVERYONE will say that but maybe some subtle misunderstanding has crept in.

A mate GerryinOz up here is about to pull the trgger on these or Wheelans and I am doing his electrics with him, so it matters a bit to me now too.

Richard, give me a call if you get a moment....I dont have your number it seems.

Cheers

DB

As far as grounding at the wing tip rib. I am planning to use sunrays and pulsars. Is there any issue with splicing the 2 case grounds, 2 black wires, and 2 shields to a single conductor then bundling that with the a shielded 3 conductor wire for the pulsars and a shielded single conductor for the sunrays back to the first rib or should 6 single ground conductors be run from the light location to the first rib?

I am very intested in Aeroleds opinion.

I just read the following off AeroLEDs support site. It appears that this may be a presentation that they did at Oshkosh this past year.

http://www.aeroleds.com/LinkClick.as...;3d&tabid=8593

I've included the whole text of this appendix, since not everyone has a VP-X, but the instructions seem reasonable for other installations as well.

bob

From the Vertical Power VP-X Pro Installation Manual

Appendix F - AeroLED Wiring Tips

Here is some information that should be helpful to builders installing AeroLEDs wingtip lights:

LED strobes operate differently than legacy Xenon strobes. Legacy Xenon strobes use a flash capacitor that charges up continuously between flashes, pulling a steady amount of current (current is continuously pulsating at the frequency of the charge pump, typically 10’s of kilohertz), then dump the charge to the Xenon tube in a single burst.

LED strobes pull their current while the strobes are lit, and pull nearly zero current between flashes.

As a result, the way that the LED strobes are wired will make a huge difference in whether or not audio frequency noise gets into your intercom. Because the current pulses to LED strobes flow in a loop with the outgoing current flowing in the outbound power wire, and the return current flowing in the ground path, there is the potential for the wiring to create time varying magnetic fields that can couple into adjacent wires such as headset jack cables, or even your antenna coax cable.

To prevent this, it is highly recommended that you follow the following wiring recommendations:

1. Use shielded wire, AeroLEDs has 3 conductor 20 gauge shielded wire available for this purpose.
2. Use the shield as the ground return. When the ground current flows immediately adjacent to the power wire, the magnetic field produced by the power wire current is canceled out by the current flowing in the shield. The ground current prefers to stay in the shield rather than flow through structure because generating a magnetic field takes energy, and the current wants to follow the path that takes the least effort because the fields cancel out (called the path of least inductance).
3. Bring the shielded wire run all the way to the panel, where the power wire can go to the switch, and the shield ground can be run to the behind the panel grounding block. If you need to break the wire run at the wing root with a connector or terminal block, that is OK as long as you resume the shielded wire in the fuselage and connect the shield grounds through the interconnect.
4. As much as possible, keep some separation between the strobe wires and sensitive cables such as intercom audio cables, headset jack cables, or antenna coax for the radios.

1. If you have a mounting bracket that is anodized (silver colored brackets), then you must remove the anodization coating from the screw wells so that the counter-sunk screw heads will make good electrical contact for making the chassis ground connection. You can test the grounding of the wingtip lights by measuring the resistance from the rear set screw head to aircraft structure ground. If your brackets are gold colored then they have a conductive alodine coating and this step is not needed.
2. You must ground at least one of the mounting screws to aircraft struture either directly or via a ground wire.
3. Tie the black ground wire, and the shield braid ground to aircraft structure ground (or wing spar ground in a composite or tube and fabric wing) at or near the spot where the chassis ground for the light is grounded. It is important that the loop formed by the black wire ground from the light, and the chassis ground from the light be kept short. Keeping this loop short is very important as it reduces radio emissions from the wingtip lights by 30db in the communications band wavelengths, both for the position lights and the strobes.

CTO, AeroLEDs LLC

Since that creates a ground loop with two points of airframe ground, I would suspect it may introduce noise issues.

Wouldn't it be best just to terminate the shield just at the firewall?

bob

I think this is most likely where I will get my improvement. I have no issues in the ICM at all, just RFI at a specific frequency. My chassis ground to ground loop is short, but not that short. I guess it would be useful to quantify "short". All the rest of the requirements as set out by Aeroleds have been complied with. Ill try this next and let everyone know the results.

Question for Stephen: any reason why you didn't co-locate the 2 grounds on a common stud? I assume its just a lack of thread real-estate.

DB, have left a message for you.

Stephen,

What's your wiring look like on the other side of that connector? Shield and airframe ground to the black wire pin or just to the shield that gets grounded at the panel?

Thanks,
Russ

Update
 

I removed my "short" separate chassis ground and co-located the chassis ground with the light ground at the mounting stud (Similar to Stephens) and all of my noise problems appear to have been solved.
I wonder how many others have followed the schematic and have a similar install to mine with varying degrees of RFI?
Also, it seems a little convoluted and not so intuitive. Im intrigued as to why the lights aren't manufactured with this in place. would seem simpler and less prone to installer error.
Cheers

This is exactly how I recommend that the grounding be done. We are making a design change that will connect the chassis and power grounds internal to the lights in future units, but the photo shown is the way I recommend that grounding be done on the current generation of lights.

Best Regards,

Dean Wilkinson
AeroLEDs LLC

Dean - thanks for chiming in here. When are you expecting the "new" grounding design to be in production? I'm hoping to use your product in our aircraft, but not at the risk of decreased COMM and NAV performance as a result of RFI. I'd like to know when this product improvement will hit the store shelves so I can avoid this pitfall.

Having been in the avionics business for a lot of years it boggles my mind that power and chassis grounds would not have been tied together internally. That's been the "magic" of DO160 compliance for decades now.

Dean what do you do with the shield at both ends? And do you run a ground wire from the light mount back to the first wig rib?

I too am curious where the shields get grounded. Also where the wire that connects on the other side of the black wire pin in Stephen's setup goes.

grounds...
 

Black wire to outboard rib... shield ground at outboard rib and firewall.

Do you have a picture of the first rib and other side of the connector? I want to see how much wire is not shielded.

Who knew that there could be so many details about connecting some lights? I think AeroLED's would benefit from further explaining their opinion of "best practices" complete with representative photos. I am not complaining, I really enjoy the research process in order to build things right the first time. I am just saying that it is hard to describe without pictures.

Shield should be grounded at one end only. Else you create two paths for ground and you may have ground loop creating noise.

Not according to AeroLeds' installation instructions. As per their very specific instructions and many VAF topic discussions, the shielding is grounded at both ends.

From a not-knowledgable but know-enough-to-be-dangerous perspective, you ground at both ends of a shielded wire if you want to keep noise inside the shielded cable, and only ground on one end if you want to keep noise from coming inside the shielded cable. Sounds good to me.

Bj?rnar is correct. If you use a ground wire and then attach the shield at both ends, you will have a ground loop. We can debate forever what evils may arise from this state.

However, that isn't what AeroLEDS recommends in their instructions. See my earlier post. They state to use the shield as ground, then there is only one path to ground.

If you use a ground and the shield, then the shield should only be connected at one end.

I would personally defer to Dean and AeroLEDS and wire exactly like they recommend.

I have tested DO-160 with the shield grounded at both ends, but you alternately can ground the shield at the panel only. I recommend that you use the shield as the return ground path if you do that as that keeps the ground current flowing in the shield adjacent to the power wires. The advantage of this is that the magnetic fields tend to cancel out when the shield carries the ground current. The magnetic field around a wire follows the "right hand rule". If you point the thumb of your right hand in the direction the current is flowing in the wire, the magnetic field that the current creates will circle around the wire in the direction of your curled fingers. Thus if the outbound current is making a magnetic field in one direction, and the return current is making a magnetic field in the opposite direction. With the current flowing in the shield immediately around the power wire, the fields are equal and nearly opposite (roughly forming around the same axis).

Shields on wires will stop electric fields, but they won't stop magnetic fields. This is why it is not a good idea to route power wires that may have dynamic current parellel to and right up against antenna or audio headset coax cables. Such routing can lead to transformer like coupling of magneticly induced noise in the coax cables that winds up being boosted by the downstream amplifier.

I have had people report both kinds of noise problems. If it breaks squelch on the radio, it is RF, but if it shows up in your headset even with the radio off, it is audio frequency. Often, the source of audio frequency noise is cables routed too close to each other (power next to headset coax).

Hope that helps,

Dean Wilkinson
CTO, AeroLEDs LLC

That is only true for low frequencies such as audio frequencies. At higher frequencies (above 1Mhz), the ground current prefers to follow the path of least inductance instead of the path of least resistance. The path of least inductance is the path that keeps the ground current as close as possible to the outbound current, which is the shield. Ground loops are a big issue for audio panels and intercoms, but for RFI it is a whole different animal.

Dean Wilkinson
CTO, AeroLEDs LLC

Still somewhat confused
 

I am installing Pulsars on the wingtips, no strobe at the tail.

Okay, I get terminating the black wire, coming from the light, at the case of the light. Then a wire is run from the case of the light and terminated at the airframe (eg: a rib) at the outboard end of the wing.

I also understand I should terminate one end of the shield at the same place (rib) on the outboard end of the wing, and the other end of the shield at my panel ground forest.

There are three wires inside the shielded cable running from the panel to the wingtip. One of the wires carries power for the strobe, one carries power for the nav lights.

I need confirmation with respect to what I do with the third wire in the shielded cable. I am assuming the "wingtip end" gets terminated at the outboard end (rib) of the wing (the 3rd wire terminated at this location), and the "panel end" goes to the panel ground (in addition to the shield ground).

If my assumption is correct, then I use up 4 tabs on my panel ground forest for my two Pulsar lights. Can someone confirm this?

The 3rd wire in the cable is the sync wire that you tie to the sync wire to the other lights (other wingtip and tail). This synchronizes the pulses for a more pleasing flash vs the 3 lights flashing out of sync.