Circuit Bending:

Here are some tips on what to do and how to do it from Reed Ghazala's more detailed guide, available in its fullest form from the Oddmusic web site here     The tools of the trade are simple and inexpensive: a small soldering iron, a set of small, non-insulated screwdrivers, alligator clips, some leads, a selection of cheap electrical components which can form the controls of your new instrument, and a drill to mount them in its case. Again, it should be emphasised that the techique is suitable only for battery-powered instruments.   "First, clip the smallest two screwdrivers in the alligator clips at the ends of a lead to give you a wire with a probe at each end. This is your most important circuit-bending tool. (Obviously, a custom test lead with a permanent probe at each end can be made for this job). Remove the back from the game or toy to expose the circuitry. Turn the device on and activate the sounds (press keys/buttons, or tape/wedge them in place to sustain sound production).   "With the device making a noise, press the tip of one of the test lead's screwdrivers to a printed circuit trace, component lead or integrated circuit pin. Keep this screwdriver tip in place for the next step. Now, with the other screwdriver at the opposite end of the test lead, begin touching various parts of the circuitry while listening for interesting changes in sound. Electricity will follow the new course you've provided with the lead. This may have no effect on the sound at all. On the other hand, the audio effect may be outrageous. Each time an interesting sound is created, note with a marker directly on the circuit board the pair of points that were connected to each other to create the sound.   "Once the travelling end of the test lead has explored the circuit's corners and all interesting connections have been noted, place the stationary screwdriver tip on a new circuit point. Again, the travelling end of the test lead explores the rest of the circuit; interesting sound-changing connections are marked. This process is repeated until the entire circuit has been searched in such a manner. Given a bit of luck, the circuit will soon be marked with a number of potential connections discovered with the test lead.     "At this point, various choices face the explorer in implementing the creative short-circuits discovered:   Direct Wiring: "Wires can be soldered directly between the points marked as pairs on the circuit board. In the middle of these wires would be soldered toggle switches so that these new sound-activating connections can be turned on and off at will. The wiring procedure begins with counting how many pairs of connections you'll need switches for. Next, decide how the switches will be mounted on the device's case (remember to check for internal clearances so that the backs of the new switches don't hit the device's internal parts when the unit is reassembled). Holes are drilled, the switches are mounted, the pairs of circuit-bending connections are then soldered through their respective switches and the device is reassembled.   Potentiometers: "Instead of switches, potentiometers (variable resistors) can be soldered in the middle of the pairs of connections. In many cases this will allow the adjusting of the new effect with the turn of a dial. Switches can be used along with potentiometers between the pair of circuit-bending connections as well. In this way, effects can be preset with the potentiometer's knob and turned on and off with the switch. A wire would be soldered to one of the points in a circuit-bending pair, through the toggle switch, then through the potentiometer and back into the circuit-board to the other point of the pair. This switched-component wiring may be used with any components, including the following:   Capacitors: "Capacitors, again available in a wide range of values, can be wired between the pairs of points. These may change the tone of the effect produced or pulse the sound in differing ways.   Photo Resistors: "These are light-sensitive potentiometers (sometimes called 'cadmium sulphide cells'): instead of turning a dial to vary the resistance and thereby the sound, hand shadows are allowed to fall upon the photo-resistors.   Solar Cells: "These are light-sensitive wafers that convert light into electrical energy. They can be used to inject their small voltage (or resistance in some situations) into the circuit between the paired bending points and thereby change the sound.   LEDs: "Light-emitting diodes are usually, for the sake of circuit-bending, used to provide low-voltage light sources. You may find points on the circuit you're bending between which LEDs will glow or pulse. These can serve as function indicators or pilot lights. An LED wired to the speaker leads may work as an envelope light also, flashing with the intensity of the sound waves.     "There are many other components that can be wired into the path of the pairs of circuit-bending points, but the above will launch hundreds of possibilities as well as pave the way towards the understanding of wider concepts."

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