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.
Огромное спасибо за потрясающие идеи!!! Буду следить за блогом, много всего интересного. А мой блог о науке, надеюсь, тоже понравится
(translation according to babelfish) Enormous thanks for the staggering ideas!!! I will follow [blogom], there is much entire interesting. But my [blog] about the science, I hope, also it will be pleased;)
Olechka-persik
9 Dec 08 at 10:53 am
Did you change any other components as well (resistors, capacitors) to make it work with a 555? I too am interested in making this, but can’t get my hands on a 551.
Marko
19 Dec 08 at 7:34 pm
No, in fact I did not change values for resistors and capacitors. Oh.. I had no 300K resistor lying around, since 330K is more common (e12? range), but that does not make a lot of difference since skin+pencil resistance can change so much. It only sets the upper limit (highest pitch). The transistors I’ve used were BC547 and BC557, since they are more common in Europe (and happened to be lying around). The speaker is quite large. I first tried the system with a piezo buzzer (from a happy-birthday-card) which also can be used without the transistor amp. It doesn’t make as much noise as the final used speaker (which was very nice and flat as you can see in the pictures)
The major difference is the power supply, since a 555 theoretically needs at least 5V (according to spec). I tried, and found it to be working quite well down to 3V.. So I used a 3.6V lithium battery, salvaged from a shakelight. I haven’t tested the durability, but it can be recharged in matter of seconds, and will be running for evenings at a row
edwin
22 Dec 08 at 5:39 pm