NDrv8r
Well Known Member
I have been looking at LED landing lights. I began to install the Vans 75 Watt MR16 lamps and realized they will about melt the wing tips off. I also realize there are a number of good alternatives out there, but I just can't leave well enough alone. the picture shown is 3 CREE MCE series lamp modules with reflectors wired in parallel. they are spec'd at 350ma each, putting out 430 lumens for a total of 1290. There are actually 4 LEDs in each module and when driven at 350 ma, there is about 12.1 volts across the module. The common way to drive these is to use a constant current source such as powerpuck. This assures that under varying voltage inputs, there will be a constant light output.
I did some testing with a powerpuck and a spectrum analyzer. It puts out a tremendous amount of radio noise right in the aircraft communications and navigation frequencies. I experimented with filtering and was able to knock it down, but not eliminate it. The nice thing is with a powerpuck is that it is very efficient. With any sort of led, you need to limit the current, so the goal is 1.05 amps to drive the three Cree led packages.
The solution is a common power resistor. The picture shows a 5 watt resistor to limit the current to around 1 amp. My RV7a has a Plane power alternator and an odyssey battery and the system runs at 14.6 volts.
Is the circuit efficient? Well, no, we are wasting about 2.6 watts across the resistor, and the resistor will need to be heat sinked, but the entire circuit is drawing 1 amp vs 7 amps for the 75 Watt MR16 lamp. I have not found a lumen rating for the 75 watt lamp, but the 3 LEDs shown are like looking into the sun!
Next is to figure out a mounting method that will either bolt on without aiming or some reasonable aiming scheme. Stay tuned.
I did some testing with a powerpuck and a spectrum analyzer. It puts out a tremendous amount of radio noise right in the aircraft communications and navigation frequencies. I experimented with filtering and was able to knock it down, but not eliminate it. The nice thing is with a powerpuck is that it is very efficient. With any sort of led, you need to limit the current, so the goal is 1.05 amps to drive the three Cree led packages.
The solution is a common power resistor. The picture shows a 5 watt resistor to limit the current to around 1 amp. My RV7a has a Plane power alternator and an odyssey battery and the system runs at 14.6 volts.
Is the circuit efficient? Well, no, we are wasting about 2.6 watts across the resistor, and the resistor will need to be heat sinked, but the entire circuit is drawing 1 amp vs 7 amps for the 75 Watt MR16 lamp. I have not found a lumen rating for the 75 watt lamp, but the 3 LEDs shown are like looking into the sun!
Next is to figure out a mounting method that will either bolt on without aiming or some reasonable aiming scheme. Stay tuned.
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