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  #281  
Old 04-25-2018, 10:09 AM
Paul Eckenroth Paul Eckenroth is offline
 
Join Date: Apr 2005
Posts: 102
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Charlie, thanks for the reply. The reason for the resistors is to simulate a filament lamp so the old style wigwag module will function. Or at least that is what I understand. The alternative is one of the high price digital modules designed to function with LED lights. Your calculated 2 watt power consumption will amount to .2 amp added current which does not seem bad to me. However my knowledge of things electrical is quite limited. Any guess as to how hot the resistor might get. Also regarding my question concerning the temperature of the heat sink, is the 170F typical and what the LEDs are designed for or is it a recipe for shortened component life. I have no idea of what is too hot for the LEDs.

Paul
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  #282  
Old 04-25-2018, 10:54 AM
Aluminum Aluminum is offline
 
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Location: San Jose, CA
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Quote:
Originally Posted by Paul Eckenroth View Post
I have checked one of the lights with the voltage adjusted to 10.3 and ended with a heat sink temperature of 170 F after .5 hour. This seems pretty hot to me so I wanted to find out if this temperature is typical.
170 F is balmy. Junction temperature is higher and more difficult to measure. Nominal life is quoted at some junction temperature near 250 F. Much higher temperature can be tolerated given the < 100 hours lifetime demand for this installation in practice--how often do you fly at night? The wig-wagging is much more stressful on the junction and the circuit than high temperature alone.





Quote:
Originally Posted by Paul Eckenroth View Post
Also I am planning on 10 W, 50 Ohm resistors wired in parallel with the lights.
Why?

Edit: nvm, saw the reply. My advice: get rid of unfit wigwag circuit, or replace with one that works without resistor.
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Last edited by Aluminum : 04-25-2018 at 10:56 AM.
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  #283  
Old 04-25-2018, 12:10 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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I'd agree with Aluminum. We had an earlier discussion about the inexpensive LED wigwag products. Most seem to require a dedicated return wire to the wigwag, but that seems a small price to pay to avoid the extra heat & complexity of the resistor. Also, wiring a parallel resistor would need to be on the supply side of any LED driver, meaning your wattage calcs should be with 14.4 V instead of 10V. Remember, LED drivers should be current sources; not voltage regulators. Not saying it won't 'work'; it just won't be right. Paralleling a resistor with an LED will confuse the current source (LED driver).
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  #284  
Old 04-26-2018, 09:03 AM
Paul Eckenroth Paul Eckenroth is offline
 
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Dan and Charlie, thanks for the info. It's exactly what I needed. As far as the WigWag module is concerned, I've looked at the commonly available modules that can directly handle LEDs. Crazed Pilot and Whelan require a ground direct from the light in order to function. The lights I am planning to use are the Kaidomain flashlight heads which ground through the housing to the airframe. I think insulating the exterior of the head from the airframe would be a problem. So I would like to use the resistor to enable the old wigwag to function. Any idea what the temperature rise might be in the resistor if used in this manner.

Paul
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  #285  
Old 04-26-2018, 09:20 AM
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rocketbob rocketbob is offline
 
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As I mentioned it earlier in this thread the difference between flashing and wig-wagging seems to be insignificant, yet to wigwag there is additional complexity and expense. In my opinion its not worth it.
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  #286  
Old 04-26-2018, 11:03 AM
Aluminum Aluminum is offline
 
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Quote:
Originally Posted by Paul Eckenroth View Post
As far as the WigWag module is concerned, I've looked at the commonly available modules that can directly handle LEDs. Crazed Pilot and Whelan require a ground direct from the light in order to function.
Well, since you are going with cheap untested chinese flashlights as essential equipment in a $100k aircraft, nothing less than Arduino with custom code to synchronize with yaw damper will do for wagging!

The PIC can forego wigging if there are no cameras present, but one must be available in the map box for emergencies per FAR 91.32768.

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  #287  
Old 04-26-2018, 11:34 AM
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Bill Boyd Bill Boyd is offline
 
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Location: Landing field "12VA"
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Default Someone has to test the waters here

Guess I'll do it.

My intention is to purchase the Perihelion potted wigwag/switch product and test same with a load of three Kaidomain flashlight heads per side. The input to the wigwag module will be 10.3V from the DC-DC switcher module that RocketBob mentioned and which I already own.

I will report results back here for posterity.

This will require waiting for Kaidomain to ship the other 4 flashlight heads, likely another 3 weeks. Eric at Perihelion assures me this should work, but a bench test is the only way to know for sure - and whether any ballast resistors will be required.

It's only .088 AMU; I can probably sneak it past Accounting
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  #288  
Old 05-02-2018, 08:13 AM
Bill Boyd's Avatar
Bill Boyd Bill Boyd is offline
 
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Default Got my lights, almost fried 'em

My remaining 4 LED flashlight heads came in from China yesterday. I promptly tore into them like a kid at Christmas and in my haste almost fried them (I think). I hooked my DC-DC module up backwards and proceeded to test the lumen output. Besides melting my retinas, I got a faint plume of smoke to come from the Cree's before I disconnected the setup (I was measuring current with my multimeter: 5.3A for a trio of them in parallel.) I think the smoke was from a minute amount of dust that had settled on them; they still light at what looks like normal color and brightness. Even so, smoke from the LED = not good!

I rearranged the multimeter to measure voltage and when I saw 13.8 I knew I had a problem. The input and output terminals of my DC-DC converter look identical but for a small silkscreened label. Did you know that these pucks hooked up back'ards just pass V-in straight through? They do

The lights are cooler, slightly less intense, and smokeless at 10.3V. Three of them should be quite the thing ganged up as a landing light. I plan to do a little investigation and look at current in and out of the DC-DC module at different output voltages as well as what the onboard current regulators in the flashlight heads are drawing. That takes lots of haywire breadboarding/rearranging if you only have one instrument for taking these measurements! I'll post results here, along with pictures.

As to the question of wig-wagging vs flashing, one additional benefit of the wigwag mode is it's half the current through the DC-DC supply to flash the LED's in alternating pattern vs together. At 5A for one side and 10A for both, we're nearing the max rated output (12A) for the converter, and I'd like to keep all components on the cool side for reliability and longevity.

Eric's Perihelion wig-wag module should arrive today and I will let the forum know how that item performs with the LED's and no shunt load resistors. We know it works fine with filament bulbs.
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  #289  
Old 05-03-2018, 10:43 PM
Paul 5r4 Paul 5r4 is offline
 
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I have the Perihelion switch on my 7A controlling the wig wag on the Baja Designs LED's. No issues. I did have the first switch Eric sent me go bad. He promply sent me another and no issues since. I always run them the entire flight. When landing after dark, I switch the WW off and turn the LEDS both on as landing lights as soon as I turn final. I know you're referring to this switch working with your lights brought to our attention by RocketBob. I don't see why it would not work just fine. Looking forward to your writeup!
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Last edited by Paul 5r4 : 05-03-2018 at 10:47 PM.
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  #290  
Old 05-04-2018, 05:20 AM
Bill Boyd's Avatar
Bill Boyd Bill Boyd is offline
 
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Good to hear, Paul. I anticipate the Perihelion envelope in my mailbox this evening.

Forecast is for rain all weekend here, so - a good time for some breadboarding and experimentation
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RV-10 - N130YD reserved - under construction

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