Minimalist IR Pen: No Soldering, Under a Minute, Under a Dollar.

My first instructable, hope it is useful:

If you want to test out the J.C. Lee (the J.C. stands for Johnny Chung, but he does kinda does miracles too...) or the Smoothboard program at www.smoothboard.net (light years ahead, because Boon Jin started where JCL ended, thanks tthe open source programming...) well... YOU NEED an ir pen.

I do theatre in English, and Magic/circus for ESL. and you can see my page (only the blog is in English the rest is in Spanish.) here.http://www.fifthbiz.com) I work with a lot of teachers that know a lot about teaching and nothing about a soldering iron. So I came up with this..)

So, for non-techies or impatient people here is a tiny pen with just one LED, a 1.5 volt watch battery, and some electrical tape that you can make in less time then it takes to play the MacGuyver theme music.

Not apt for using with small children (because these are easy to eat) this is a good STARTER pen, but I think you will want to upgrade.

Nonetheless, these ROCK for a screen with projector and wii-mote behind, and with one in each hand... and for testing the Wiimote IWB for the first time.

Materials:
https://www.instructables.com/files/deriv/FL3/HQXG/FXA3D45B/FL3HQXGFXA3D45B.MEDIUM.jpg

1. ir led at 940 nm (i used a Vishay TSAL6400) which runs on 1.2-1.6 v costing14 centimos of a Euro, as I'm in Spain, it would be under 20 US cents , I think)

2. watch battery at 1.5 v (50 centimos/70 cents)

3. Electrical tape

4. Scissors.

5. Mobile phone with camera, webcam or digital camera (to check things out.)

Step 1: Understanding and Preparing the IR LED.

Getting the LED out.

Two basic concepts are essential.

1. The light is invisible to the human eye. (Infra-Red - below the red spectrum, the lowest visible light we can see.)

It is not invisible to a digital camera that is not protected against the IR spectrum, ie: mobile phone, digital camera or webcam, so we can use that to check things out.

2. The LED is polarity sensitive. �
You have to connect positive to positive, and negative to negative for it to work. The negative is the shorter leg of the LED. (To remember: Being short is negative for LEDs.)
https://www.instructables.com/files/deriv/F0K/ARID/FXA3D45C/F0KARIDFXA3D45C.MEDIUM.jpg
Preparing the LED.

On my watch battery, the positive side was flatter. So I bent the negative side to use as my trigger.
https://www.instructables.com/files/deriv/FE0/0D2B/FXA3D45A/FE00D2BFXA3D45A.MEDIUM.jpg
I then made a "v" bend (two would be better) in the positive (longer) wire, that goes flat against the battery to keep the LED flat and stuck to the battery in the next step, instead of falling out of the tape.
https://www.instructables.com/files/deriv/F30/NVOC/FXA3D458/F30NVOCFXA3D458.MEDIUM.jpg

Step 2: Bringing It Together...

Here we isolate and attach the positive ends of the LED and battery.

Keeping the negative end out of the game... tightly wrap the two positive ends with electrical tape. You could also bring in a glue gun in now to make it prettier. (but you won't be finished in under a minute)
https://www.instructables.com/files/deriv/FN8/9KJ7/FXA3D457/FN89KJ7FXA3D457.MEDIUM.jpg
You now have a trigger against an isolated surface, so all you need to do is...

Step 3: Cut Your Hole for the Trigger. You Are Soooo Done.

With scissors or a cutter, you remove the tape under the negative wire of the led.

The wire should be stiff enough to maintain its shape.
When you press, it should light up. Check with your mobile phone, or camera, if it doesn't check your hole, your led, and the polarity of the whole thing.

You now have an IR Pen.

Not a beauty, but you can attach it to your index finger with a band aid and no one will really see it.

If your surface is very tough and smooth, you may be able to use it as a pressure sensitive tip, but I prefer the thumb to avoid scratching stuff. (A drop of glue gun shtuff on the trigger would make it softer on the surface or your thumb. You could make a quick mold by shaping a hole in plasticine, filling the glue in, and then placing the trigger inside, to avoid isolating the trigger end. But would Dean Richard Anderson do that? NO! McGuvyer would probably substitute the tape for chewing gum, because his saliva doesn't conduct electricity.)