DrawDio

I came across the drawdio at ladyada.net and drawdio.com. Again a wonderfully simple idea, but very imaginary and creative! I made one as Sinterklaas-present for my mother. I didn’t have time to buy a kit, so I had to use parts that were lying around. Using the schematic Limor posted on her site I made the design on breadboard. Instead of the low voltage NE555 (TLC551?) I had only a normal 555 lying around, so I couldn’t use a 1.5V battery but used a 3.6V lithium cell from a salvaged shake-light instead. The speaker was taken from a toy-piano. The polycarb bulb can be bought in craft-stores. Instead of the american type 2n** transistors I used the BC557 / BC547 types that are more common in Europe for the amplifier stage. Be aware: in the schematic limor posted, the pinning of the 555 is not logical (swapped pins) and the amplifier stage is displayed wrong (the one posted on the bottom of the site with the pnp at low side and npn at high side is the correct scheme for the amplifier). This version of the pen in action: check youtube.