By now, unless you have been living in a deep dark hole of non-geekdom, you've probably heard of Johnny Lee's incredible experiments with the wii remote or "wiimote". Basically, he has discovered a way to turn a $30 wii remote and a small light pen made at home in to a multi-touch whiteboard technology that can be adapted to any surface. I had to give it a try.
First I needed a wii remote, because I don't currently own a wii. I found one on eBay for $29.98 shipped. Next I needed the components for my light pen. A trip to Radioshack and a local art supply store took care of that. It's funny to see how Radioshack employees react when you ask them how to calculate the right resistor for your LED.
The formula for that btw is:
R = (V1 - V2)/I
V1 = The voltage of the battery
V2 = The voltage rating of the resistor
I = The current of the resistor in Amps
Here are the components I used from Radioshack. The cost is higher than if I would to have ordered from a somewhere else, but for a prototype it's nice to just be able to go down the street:
Lithium 3V CR1220 (230-0188) $5.49 (probably over kill)
5mm IR LED 940nm (276-0143) $1.99
P/B Switch SPST (275-1547) $0.87 (I bought a pack of 4 at $3.49)
10OHM resistor (271-1301) $0.20 (I bought a pack of 5 at $0.99)
For the casing, I saw Johnny Lee using a dry erase marker at his TED talk and realized you could fit all the components inside as opposed to using a Bic pen and needing an external power supply. However, dry erase markers are expensive. I was about to buy a back of 3 for about 8 bucks when I found hidden in another section the "Mr. Sketch" scented markers. They are the exact same shape as dry erase markers and much cheaper. I bought a pack of 8 for $5.49.
The total cost of my light pen: $9.22
The total cost for the entire project: $39.20
Cost of a standard electronic whiteboard: $2,000
Now I needed the software to run my whiteboard. I have a mac and Johnny's Wiimote Whiteboard software is written in C# for Windows. Luckily some smart people ported the software to java and also created an OS X native version. I used the OS X version.
The light pen was constructed with lots of trial, error, solder, and electrical tape. You can see in the video demo, I taped the contacts to the battery and later just shoved it in and recapped the bottom of the pen.
One cool thing I learned while surfing discussions about the light pen is that you can test your IR pen using a camera phone. The camera phone will pick up inferred light. You can see this in the video of my light pen.
Here is my light pen up close:
Here is a demo of the whole set up: