IR LED ballcap

I'm a veteran tinkerer. I mess with all kinds of technology, and may have some insight into how this could be accomplished.
I'll try to describe how to put one of these together. I'll write it out as if I'm describing it to a bunch of Cub Scouts who've never even seen a soldering iron (I have some experience doing that), so it may be overly simplistic or seem to be condecending to those of you who have tinkered with electronics before.

The basic idea is to rig a ballcap with a series of Infrared LEDs in order to cause any surveillance cameras pointed at the wearer to see a "flare" instead of the wearer's face. This is made possible by the fact that most digital cameras used for surveillance use "low-light"Charge-coupled Devices (CCD's) to capture the image and these CCD's are sensitive to infrared (IR) light. The camera will "see" the IR light better than visible light, causing it to register a bright spot where the IR is coming from compared to the area around it.

Supplies needed.
IR LEDs- eBay has them. $5.00 for 50- enough for five ballcaps or one cap and spares to play with later. LEDs are Light Emitting Diodes and like any other diode, will only let electricity flow in one direction. Think of them as check valves. This means that each LED is going to have a positive and a negative leg. The negative leg is ususally indicated by being shorter or by having a wide part near the body of the LED (if I remember correctly- most of my tinkering is done with salvaged parts, so I just check them before use)
Power supply- the LEDs I've seen on eBay run on 1.5- 1.6 volts direct current (VDC). Amazingly, this is what you'll get out of a standard or alkaline battery. Since you want to be able to wear this on your head, we'll try to save weigh and use a single AA battery. If your LEDs need a different voltage, just stack up batteries (positive to negative) and add the voltages until you get what you need.
Switch- in order to save battery life, you want a way to turn things on only when you need them. Any small switch will work with 1.5VDC.
Wire- you need to get the power to the LEDs somehow. Ten, 5mW LEDs will draw 50mW (milliwatts- thousandths of a watt), so any wire you can work with will do. Keep it small to save weight- look for some scrap phone wire or sacrifice an old ethernet cable. Solid copper will work better than stranded wire, but is harder to solder.
Attachment- for semi-permanent use, a hot glue gun would work just fine. If you want to do a "covert" job, you'll have to tear out some stitching and re-sew the bill of your ball cap.
Soldering Iron- you'll need a low-power soldering iron to make the connections. Use a 15 or 20 Watt iron to aviod burning up the LEDs. If you've never used a soldering iron before, practice connecting two pieces of wire laid side-by-side until you're comfortable with it. Basically you need to heat up both wires while resting the solder on them (not on the iron) until the solder flows between them. Remove the iron and let the solder cool before moving the wires. I should warn you that soldering irons run over 700 degrees F, so be careful what you let them touch.
Solder- use fine (.020-.040 inch) rosin-core solder. Do not use plumbing solder- it has an acid flux core that will corrode your connections.

OK, now for the fun.
Checking a convienient ballcap, I've found that the bill has plenty of room for ten LEDs spaced an inch apart. On a clean, protected area of the kitchen table, lay out your ten LEDs in a line, about an inch apart. Keep them all oriented so that the negative legs are all on the left side. If they don't want to stay put, use some Fun-Tack, Play-Doh, or anything else you can find to keep them from rolling around.
Take a piece of wire about two feet long and solder one end of it to the negative lead of the LED furthest to the right. Strip back some of the insulation (about a half-inch gap) two inches from the LED and solder the bare copper to the negative lead of the second LED. Repeat until you have all of the LEDs' negative leads daisy-chained together. Take a second piece of wire, this one a few inches longer, and do the same thing to the positive leads. This should stiffen up the whole mess and make it easier to work with later.
Solder a short piece of wire to the negative end of your AA battery (the flat end). This may take some trying with a low-power soldering iron, just give it time. Solder the other end of this wire to one of the posts on your switch.
Solder the free end of your negative-lead wire to the other post of your switch.
Solder the free end of your positive-lead wire to the positive end of your AA battery.
If you have a digital camera or even a cellphone with a camera, you can check your work by pointing the camera at the LEDs and turning on the switch. The IR LEDs are invisible to your eyes, but the camera should show them as bright spots. If they all light up on the first try, congratulations, you're doing better than I usually can. If some of them don't light up, try de-soldering them and switching the leads around- you may have put it in backwards. If none of them light up, check your battery and switch.
Once you have it working on the table, all that's left is to mount it under (or in) the bill of a ballcap. I say under the bill of the cap because any camera that can see your face would have to be able to see under the bill of a cap. It would also draw less attention if they weren't visible during the day. Use a hot-glue gun to attach the LEDs pointing out, being careful to not cover the front of the LED with glue. Keep the bare leads seperated to avoid short-circuits. Personally, I'd use the leads to hold the LEDs in place, covering them with a glob of hot glue to provide insulation. Tack the wires as needed and stick the switch and battery wherever they'll be comfortable for you while you're wearing the cap.

If I can figure out this damn CAD program, I'll try to post a wiring diagram and maybe even a sketch of how I see this being put together. Feel free to improvise and improve. Use a battery holder instead of soldering directly to the battery. Drill holes in the bill of the cap and mount the LEDs the way you want to. Play with it- that's the fun of tinkering!

ranamacar