Building an InfraRed Pen
To build an IR Pen you will need the following materials:
IR LED, switch, battery pack and a marker of your choice for housing. All parts except the marker can be purchased from Radio Shack (or fry’s or any similar electronic parts store), a total of $12 buys material to build 2 Pens.
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Resources:
terracode.com
projectshoestring.blogspot.com
johnnylee.net