Page 79
VP-X Installation and Operating Manual
Rev. D (August 5, 2020)
Appendix E – 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 for the older multi-voltage
lights:
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 avionics ground. 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. Gounding to the structure near the light is not recommended.
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.
Note that the above recommendations are primarily intended to prevent audio frequency signals from getting into your
intercom. For preventing RFI, you should also follow these recommendations:
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 structure 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.
If you have wired your plane, and didn’t follow all of the above recommendations and think you have an audio noise
problem, we can provide in-line filters that you can put in each wingtip that will help to reduce the edge rate on the current
pulses, but ultimately the best way to handle it is to prevent it from occurring in the first place.
Dean Wilkinson
CTO, AeroLEDs LLC
