Post Title: Rolling My Own Wig-Wag Circuit
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Mon, 11 Oct 2010 21:30:27 +0000
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Over the last couple months, I've been eyeing various landing and taxi light setups, trying to figure out what I want to do for my airplane.
I"m not super keen on the leading edge landing/taxi light setup right now, so I want to focus on putting all the lights in the wingtips.
There is a
Van's wingtip landing light kit that puts two MR16 sized bulbs in each wingtip. Supposedly, you can aim one set forward for landing (also recognition) lights, and aim the other set down for taxi.
I've read on the forums that people haven't been too thrilled with this setup using the standard 35W and 50W halogens that van's provides. Something about not getting enough light on the centerline of the aircraft, where you need it for landing.
I have also read, however, that with the MR16 HID upgrades from somewhere like
www.planelights.com or
duckworksav.com, there is plenty of light to go around.
Sweet. I'll go with those. (This is the same as
Mike Bullock's setup, except instead of both sets being 50W, I'll probably use one set of 50W HIDs for landing, and use a 35W (pronounced “less expensive”) for taxi lights.
But then we come to wig-wag. I think wig-wag (pulsing lights) for the landing lights is a requirement safety wise, so I am planning on incorporating a wig-wag circuit into my landing lights.
I could just wire them in parallel, so you turn the landing lights on, and either wig-wag them or not depending on wig-wag switch position, but because these are going to be HID bulbs, one needs to warm the bulbs up before pulsing. (I've read that 25 seconds was used previously on HID flashing circuits, so I'm going to use 30 seconds for now, but I may bump that up based on a crude bulb temperature test I may set up in the future.)
Procedurally, I could just wait 30 seconds after turning the landing lights on before turning on the other switch, pulsing them, but who can remember that 100% of the time? 30 seconds is just about the time it takes between turning the lights on for takeoff and liftoff. This is not the right time to be reaching down for another switch.
I'd rather flip both switches ON, and have them automatically warm up before starting to pulse.
Enter xevision. They have a
multiple-hundred-dollar HID flasher box that will work great for this application.
Except I'm an engineer, and I love a good problem to solve, and I don't have hundreds of dollars laying around.
Enter Microsoft Visio and B&C. Using
Bob N's Low Cost Wing Wag Alternative document (page 2.0) as a starting point, I drew up a concept for a landing and wig-wag circuit with a delay timer (haven't figured out the timer circuit yet, but it's a relay trigger, so I'm going to simulate it with a switch for now).
Keep in mind, I could combine the functions into a 2-10 switch (similar to page 3.0 of the wig-wag document), but then I couldn't use the switch-breaker I'm planning to use in place of the regular switch I have depicted. Maybe this circuit is a good candidate for an inline fuse…I'll sort that out later.
Anyway, here's the circuit for now (since I am a wiring novice, I'll have to figure out how to connect 5 wires to one switch terminal later…I know you can't just bolt them all on there.)
<h2emstrong>SEPARATE SWITCHES (see below for single switch diagrams)</strong/em/h2>
Oh, and I've shown the HID lights here as just normal lights. You get the idea, though.
UPDATE: After testing, I realized I need diodes in here on the flasher side of the 2-3 switch near the NC part of the relay to isolate the two lights. I'll try to draw them in.
Both switches OFF.
+14V will come in to the left, and the lights will be connected to the center terminals of the 2-3 switch in the picture. the fast-on connector at the top of the picture will eventually be connected to a timer circuit that will close the relay (top left) after 30 seconds.
It was too late to start hooking stuff up. Now. Back to the tools. I ran off to Lowe's (after considering buying these things on eBay...no, they need to be sharp, and Lowe's has the name brand one I want), and bought the STRIPMASTER.
Seriously. That's the name you come up with?
A closeup of the important bits.
This is instead of about 60 seconds worth of stupid tool-knife-stupid tool-hurt hand-knife again-stupid tool just to strip one end of one wire.
Okay, let's find some lights and start pushing electrons around!
These will do. 12V, 50W. (Enough for a spare for this little experiment.)
Oh, and the wood is so you don't start melting the nice carpet you've purchased for the workbench top. Ask me how I knew to do this.
Wuhoo! It's alive!
Okay, let's hook up my circuit.
This is LDG ON and WIGWAG OFF.
Sweet. Electrons are still flowing.
But. This is where bad stuff starting happening.
I threw the WIGWAG switch to ON and then used the simulated timer circuit to close the relay. Nothing happened (lights stayed on).
After a little more investigation, I figured out that both the normally open (NO) and normally closed (NC) contacts were getting +14V all the time. Tha'ts not good. (I knew I needed some diodes or something. I'll investigate further seperately.)
During the investigation, I wanted to make sure that everything works as advertised.
It's making a weird buzzing noise, and the first light comes on, then the second one starts to come on, but it doesn't really finish a singe cycle. I'll have to email the aeroelectric list about it and see what they say.
Since I didn't get that huge satisfaction of a completely working circuit, I grabbed an automotive flasher I had on the shelf.
It's the wrong flash pattern, and it won't work with alternating lights, but it's still cool.
Finally, I bypassed the B&C flasher and checked the relay operation.
First, I turn on the lights. Then, I turn on the wigwag, and the lights stay constant. Third, I'll close the relay so current flows through the flasher (although since it's not hooked up, the lights should turn on.) Let's see what happens.
Wuhoo, my one electrical engineering class in college has paid off!
This was about an hour's worth of work, and since it's ultimately for the build, I'm going to count it as R&D time.
1.0 hours.
Oh, and the next day, I hooked just the wig wag portion up to my car battery, and it worked (I wonder what's going on with my power supply...).
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It's a little fast for me. I wonder if there is a way to slow it down.
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