The Art of the Creative Short Circuit

Jan 1, 2003 12:00 AM, By Qubais Reed Ghazala

           
 

A Beginner's Guide to Circuit Bending

Reset switch. Whether it's your PC or a Speak & Spell, systems crash. In order to reset a bent circuit, install a “normally closed” (NC) push-button switch to interrupt the voltage supply from the battery compartment. Begin by searching for a battery wire to clip. If you cannot locate one, you will have to study the circuit and find a power-supply trace on the board to cut. Next, solder the switch with a wire to each side of the cut trace.

To find an easier soldering point for the wire, follow the trace to the next component or scrape the trace clean on either side of the cut and melt a small blob of solder onto the trace. Then, solder the wires to those blobs. Be sure to mount the switch in a place where you won't hit it accidentally.

FIG. 4: Once the wiring is completed, you’re ready to put the batteries in and test your Incantor.

Line outputs. Line outputs are important if you want to experience the full potential of an instrument's frequency range (which often far exceeds the capability of the built-in speaker). Adding a line output also opens the unit up to external signal processing.

A suitable line output can usually be derived from the wires going to the speaker. Simply mount the output jack of choice on the case and solder new wires to it that come from the speaker terminals. Then, plug the instrument in to a small amp to check the output level.

Slowly turn the amp up. If the signal is too hot, add a trim pot to one of the wires going to the new jack you installed and adjust it accordingly (1 MΩwill probably work).

Replacing components. In addition to creating new circuit paths, you can replace the components on a circuit with ones of a different style or value. For example, a standard resistor on a circuit board can often be replaced with a potentiometer or a photo cell (both are variable resistors). If the component is a resistor that sets the pitch of a voice (which is common), that voice now becomes tunable, allowing you to change frequency with the turn of a dial or the shifting of light. Similarly, you can replace a potentiometer with a photo cell. Motion sensors—such as mercury, boxed ball, and tilt switches—can be wired into small devices for dance or gesture-driven instruments.

To address space limitations when mounting new controls, completely remove the circuitry from its original housing and install it in a new enclosure. Or, construct a remote-control panel to hold the new switches and dials and connect it to the original circuit by means of a braided or ribbon cable.

The author’s Photon Clarinet includes a pair of external controllers.

For those situations in which there is limited space in which to solder—as with short component leads and IC pins—study the circuit to see if the area you wish to solder to is connected to a trace on the board that's easy to get to. A resistor lead within a circuit that is hard to get to, for example, might connect with a printed circuit trace that emerges, with full access, on the other side of the board. Soldering to a trace that connects to the desired component elsewhere is the same as soldering to the component lead itself. This technique can be a real problem-solver for tight spaces.

Many additional components can be wired into the path of the pairs of circuit-bending points. But the above will get you started on your way to discovering hundreds of possibilities as well as toward understanding wider concepts.

TEST BEFORE YOU SOLDER

You can use a modified test-lead system to quickly test the various components between the pairs of contact points. Such a system consists of the two screwdrivers as before, two alligator-clip test leads instead of one, and the component to be tested (potentiometer, photo cell, LED, and so on).

Clip a screwdriver at one end of each test lead. Next, between the empty ends of each test lead, clip the component to be tested. The screwdrivers again serve as probes with which to search the circuit, but now you are sending the signal through the component that is clipped between the two leads.

The wiring procedure begins when you determine how many pairs of connections you have, the types of components you want, and how many you'll need. Then, you can decide how and where they will be mounted on the device's case. (Remember to check for clearances so that the backs of the new switches don't hit internal parts when the unit is reassembled). Next, drill the holes, mount the switches, and solder the pairs of circuit-bending connections through their respective switches.