Drawdio

The drawdio is a small device that is attached to a pencil, when thick graphite lines are made with this pencil and one puts their hand not holding the pencil on one side of line and keeps the tip of the pencil on other other side, it will emit a loud pitched noise. What is happening is that the battery starts the current into the system, first it passes a resistor, this “slows” the current and makes it weaker. It then continues to a couple of capacitors which store the current and then release it, this is to further control the current and voltage. Then comes the TLC551 which is the chip in the center of the board, the 551 is a timer and it oscillates the current between flowing and not. The current flows into a bigger capacitor that fills up and empties as the 551 oscillates. This quick oscillation is what makes the noise, although by itself it is not strong enough to make audible noise. To correct this it then passes through an amplifier and then to the speaker. Then it passes through two more resistors and on to a tab. Copper tape is connected to that tab and is attached to the pencil with a tack so that it is also touching the graphite of the pencil. At the other end is another tab with more copper tape that winds around the pencil to where the hand that is writing can touch it, this tab is connected to the other side of the battery, so when one hand is touching the graphite and the other the copper on the pencil the circuit is complete and noise happens.

Drawdio

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