Dale Dougherty - Homegrown Drones

Build Drawdio, a simple electronic sound synthesizer mounted on a pencil

Designed by Jay Silver, then a student in the Lifelong Kindergarten group at the MIT Media Lab, the Drawdio circuit plays a musical tone with a frequency that varies based on the resistance between two points. The wire wrapped around the pencil handle is one point, and the pencil lead itself is another. When you hold Drawdio in your hand, your body becomes part of the resistive loop, and you can do all kinds of fun tricks, like draw yourself a piano and play a little tune!

The Drawdio circuit is based on the classic 555 timer chip. To save space on batteries, were using a more modern low-power version of the 555 that will run on 3 volts, but otherwise it behaves just like a standard 555. Wired like this, the 555 operates in so-called astable mode, outputting a continuous stream of pulses from pin 3. The frequency of those pulses can be controlled by changing the values of the resistors and capacitors connected to pins 2 and 7. Since the contacts are arranged to put the users body into the resistive loop, the frequency output by the 555 naturally varies depending on what she or he is touching. The transistor amplifies those pulses, which emerge from the speaker as audible sound.

Sean Michael Ragan, MAKE Technical Editor; Michael Colombo, MAKE Online Contributor

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Test-fit the components on the perfboard.

Cut and strip the grip and graphite leads.

Solder the components and attach the speaker to the perfboard.

Attach the perfboard and battery holder to the pencil.

Secure the graphite lead to the top with a thumbtack.

Secure the grip lead with electrical tape.

Learn to build an analog sound synthesizer that piggybacks on top of a pencil!

TLC555/TLC555CP LinCMOS timer (8-pin DIP)

Parts list:

Electrical tape

Perfboard

0.1F ceramic disk capacitor

Battery, AAA (2)

TLC555/TLC555CP LinCMOS timer (8-pin DIP)

Thumbtack, flat, metal

PNP amplifying transistor

Battery holder, 2 x AAA

Resistors 1/4W - 10M, 270K, 10K, 10

8 mini speaker

Double-sided foam tape

Hookup wire, 22AWG solid

100F 35V 20% radial-lead electrolytic capacitor

Pencil, flat with soft lead

560pF disc capacitor

2 AAA battery holder

PNP amplifying transistor

Tools checklist:

Pliers, mini long-nose

Wire stripper / cutter

Soldering iron and solder

Scissors

Utility knife

Straightedge

Green florists foam (optional)

40 watt pencil iron

For complete instructions and details on this project visit:

radioshackdiy.com/drawdio

One finds limits by pushing them.

Herbert Simon

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