Clock Tickling

index
555 touch sensor
air mike
amplify your toy
box your toy
circuit sniffing
clock tickling
contact mike
electret mike
hack the clock
laying and hacking
laying of hands
light theremin
make a cable
mapping
pickup
piezo driver
resistors
soldering
sudomini
synthesis
tape head

Hacking is like hot-rodding your car: you don't need to be able to build a care from scratch to swap in a 5-barrel carburetor, but it helps to know what a carburetor looks like before you get too creative with the wrench. We'll use a simple but very useful hack as a way to learn how to identify basic electronic components and introduce some electronic axioms.

You will need:

• An electronic toy;
• Small screwdrivers;
• Fine-tip permanent marker.

The toy should be expendable, not too small, have a built-in speaker and it should make sound. Sampled sounds (like voices, animal sounds or instruments) are more useful than simple beeps. The more buttons and switches the better, although musical keyboards often have limited potential for interesting modification. They must be battery powered.

Most electronic toys manufactured since the 1980s employ a simple clock circuit thta determines the pitch of its sounds and speed of its blinking lights, graphics and/or program sequence. This is true for most toys using digital circuitry and many analogue circuits.

Open up the toy, carefully noting wire connections in case one breaks. Study the circuit board and try to identify the following types of components: Resistors (cylinders encircled by stripes), Capacitors (small discs or squares, or fatter cylinders), transistors (three wire legs supporting a small plastic blob or metal can), diodes

As with the radio hack we did earlier, your fingers are often the most direct form of circuit manipulation and testing. Get the circuit making sound. Position it so that you can touch the solder-side of the circuit board, if possible while looking at the component side. Lick a finger a place it across various connections, in particular try to connect across points at either end of a resistor, so that your finger parallels the resistor's connection. When your finger bridges a resistor that is part of the clock circuit you should hear the pitch slide up a bit, or the tempo speed up. If the circuit has lots of connections and you are having trouble finding the spot, concentrate on those resistors lying close by small capacitors. When you think you've found a hot spot, mark it...

Electric current flows through wire like water through a fat pipe. Resistors are like skinny pipes - the higher the resistance (Ohms), the less current flows. Capacitors also resist the flow of electric current, but resist it more at some frequencies than others, in a manner that defies liquid analogies. Capacitance is measured in soukable Farads, usually in small enough amounts to be called microfarads or picofarads.

When a resistor and a capacitor are combined with a little bit of amplification they oscillate at a frequency that can be adjusted by changing the value of either of the two components. Make either of them smaller and frequency goes up; make either larger and the frequency lowers.

When you place one resistor in parallel with another you lower the net resistance. Your skin is a resistor - when you press your finger across the circuit board contacts you effectively decrease the size of the resistor on the other side of the board. More current flows and the pitch goes up.