Hardware Hacking 67sometimes work even without power hooked up.) When in doubt, triple check
all connections.
You could use any of the six sections interchangeably, so this is as good a time as
any to get familiar with schematic representation, which conveys a circuit design
independently of the physical arrangement of its components of a board:
The translation from this symbolic schematic to the mess of wires and
components on the board may not seem obvious at first, but once you get more
familiar with the language of electronics you’ll see that the schematic is an useful
way to represent the way a circuit functions, rather than just the way it goes
together.
- Substitute different resistors and capacitors and listen to the effect. Take a pot
or photocell and substitute it for the fixed value resistor – the wiggly resistor
symbol in the schematic above can be taken to mean any form of resistor,
including variable ones such as pots or photocells. The capacitor determines the
range through which the variable resistor will sweep the pitch. Too small a
capacitor (less that 0.001uf) and the circuit will make sounds that only dogs &
bats can hear. Larger values (greater than 5.0uf) lowers the pitch range to that of
rhythm -- you’ll hear the oscillation as a tick-tock instead of a buzz. A photocell
turns this simple oscillator circuit into a wonderful, Theremin-style instrument
controlled by light and shadow.
When you use a pot you will notice that at one extreme of the rotation the pitch
will go too high to be heard. It will also drain much more current at this
ultrasonic pitch, and shorten battery life. Therefore you may want to put a
modest resistor (try around 10kOhm) in series with one leg of the pot to set a
maximum pitch that is within the range of hearing, as we demonstrated in
Chapter 14.