I have a model airplane application in which an LED is driven directly from a PIC16F628A. The LED flashes about 1 to 2X per second only when it is safe to launch the sailplane.

The problem is that in bright sunlight, it is difficult to see whether the LED is flashing, because sunlight scatter off the lens is too bright. The work-around is simply to shade it with one's hand, but that is not always practical for someone who is about to launch a sailplane from several feet away. A permanent shade might work, but adjusting it so everyone involved in a launch can see the flashing LED might be tricky. A wide angle of view is needed.

I am looking for recommendations for other low-current signaling devices that might work. I've thought about a rotating drum or disk. Does anyone know of LED, liquid crystal variants, or other devices that might be more easily seen in in bright sunlight?

Thank you. John

 

go to the local photomat and grab some disposable camera shells. rip out the photo strobe circuit, and replace the shutter switch with an SCR driven by your PIC.

maybe put the strobe behind some colored cellophane to give it more of an eye catching color.

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Strobe circuit needs some higher Voltages to operate.

Whats the power supply battery voltage you supply?

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The strobe is a good idea from the standpoint of visibility, but I would be concerned about two things: 1) In our application, it would be flashing continuously for 4 hours or so per day X3 days per week -- it may not last long; and 2) Distraction from flashing in one's peripheral vision. The latter may be quite important while flying. Some people use beepers, which can be distracting.
They can be turned on/off as needed, but I was trying to avoid that. As silly as it may sound, I have seen people try to launch while the winch was turned off and not beeping -- fortunately, nothing bad happens then.

Our power supply is a 12V marine battery. A small pager motor with a black/white disk on the shaft was one of my thoughts, but again, longevity may be a problem.

I was hoping someone could come up with a unique approach or know of recent developments in LCDs/LEDs/or whatever that would improve viewing angle and visibility in bright daylight. John

 

so you want something to catch your eye sometimes, but not catch it other times? that sounds like a contradiction to me

grab a five watt prolight star led from www.besthongkong.com, mount it to a generous heatsink and see how that works for you.

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I have some of these LED moduals -
http://www.goldmine-elec-products.co...p?number=G9987

They are quite bright, sealed, and have a built-in sunshade. Viewing angle is pretty wide, but depending on your application you might need several to make them viewable from 180 or more degrees.

The red are superbright and work off 12V, the green aren't as bright and need 18v, so you would need a boost IC of some sort to run off a 12v battery. The red might be bright enough though, they are blinding up close.

Could you you also set up the PIC to slow the flashrate down? how about 2 or 3 quick strobes and then a few second pause. That would help save battery life.

 

Is this mounted on the plane or launcher?

 

Actually, I don't think it is contradictory. Maybe, it was just not explained well. I want it to be easily visible when looked at, but not distracting when just in one's peripheral vision. Our vision, particularly peripheral vision, is quite sensitive to flashes and rapid movements. It's an evolutionary thing that is easily demonstrated with an old monitor at low refresh rate. It can be very distracting, which is good, if you don't want to be dinner, but bad, if you want to concentrate on flying.

The light is located on the launcher, not the airplane. If the light is not flashing, it means the retriever for the launch line is not properly set...which will result in a VERY short flight .

Thank you for the suggestion about the LED with a built-in shade. I didn't know they were made and will look them up. I tested red, green, white, and yellow LEDs, and red was the most easily seem. As for the 12V, that is the maximum from the battery. Currently, the LED runs directly from the PIC, so it is limited to 5V and the max. pin current. However, using that to drive a simple transistor so I can access 12 V and more current is not a problem.

Thanks. John

 

A disposiable camera flash is 1.5 volts, but draws a lot of current. Modified as a strobe, it takes 6-8 seconds to flash. Haven't tried changing the capacitor for a faster rate...

 

If you want it to charge faster, supply it a higher voltage. Never tried this but flasher circuits are both cheap and incredibly simple. Even just a half volt more might work.

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hmm, the human eye is much more sensitive to green than red. unless the green led's are much less brighter than the red. That's strange?

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Thats what it is. The green are much dimmer then the red. The reds are blinding.