While attending the World's Maker Faire a few weeks ago, I was fortunate enough to get one of the freebie drawdios before they were all gone.
The drawdio is a little device that attaches to a pencil and makes an electrical connection to the graphite on the non-writing end of the pencil. The device also makes contact with the users hand via self adhesive copper tape in the area where the user grips the pencil.
You opperate the drawdio by drawing on paper with the pencil. As you draw, the device outputs sound of a varrying pitch and intensity. Once the drawing has been started, you simply place a finger from the hand that is not holding the pencil on your drawing and draw with the pencil.
The device depends on a very small current which passes from the device, into the grapite of the pencil, then through the graphite on the paper (your drawing), then through the finger that you placed onto the drawing and finally returns to the device through your hand that is holding pencil.
I have been wanting to get my hands on one of these for a while but had always thought that the price tag was a bit high so getting one at the Maker Faire was serindipitous.
The electronics on the device consist of a 555 "timer" IC, a few resistors, capacitors, a transistor, a speaker and a AA battery. The kit came with all of the components and a small printed circuit board to solder everything onto. I had a tag sale at my house today so I had an opportunity to throw this together
Everthing went together easily however I would recomend that anyone attempting to assemble this kit use a soldering iron with a fine pencil tip as opposed to the wide chisel tip which I had used. Also I need to get some better cutters that will allow me to trim leads closer to the board.
Another tip that was not indicated in the instructions is that the battery polarity must be correct for the device to opperate. Strangely, I had tested the device with the battery holder in the same orientation as the picture provided with the instructions however I had to reverse the polarity to get it to work.
Here is a little closer look at the device mounted on a the pencil.
Overall, this was a simple build and would be a good project to do with younger makers for soldering practice and as an introduction to IC's.