"Hairball" Circuit Bending Element

Circuit Bending: An idea pioneered by Rheed Ghaza of connecting circuit nodes together that were not originally designed to be connected. A resistor is usually used in series to prevent excessive current flow and act as a resistive mixer. Results are frequently chaotic because of non-linear response caused by feedback.

Any resistive type element can be used including potentiometers and switches with series resistors. Photoresistors have advantages because they are inexpensive and groups of them can be varied by a single light source. This page discusses building an array of 5 photoresistors controlled by a single LED light source. Inexpensive parts from Radio Shack are used for ease of access.

The idea was partially inspired by Jurgen Haibles "hairball" in the Neptune Phaser

Parts:

Radio Shack CDS photoresistor assortment. Part Number 276-1657 Webpage

Radio Shack Super-bright 10mm LED. Part Number 900-6119 Webpage

Radio Shack 5-minute Epoxy Glue Part Number 910-5123 Webpage
Any 5-minute Epoxy will do - does not need to be Radio Shack

Black or Gray Modeling Clay "Sculpey"

Duct Tape or any adhesive tape

Step 1:

Find a photoresistor pack with 5 identical photoresistors, or buy multiple packs. Take 4 photoresistors and tape them to the cardboard back of the package in a square configuration. Insert the LED in the middle with the leads sticking up. Cover with 5 minute epoxy and let epoxy harden.

Step 2:

Peel the hardened epoxy off of the cardboard. Some paper will remain, remove the paper by wetting with water and rubbing so only the clear epoxy and LED are left. Dry the surface and glue photoresistor #5 to the top, opposite the LED leads and let epoxy harden.

Step 3:

Cover the whole assembly with Black Modeling Clay. The original idea was to use black bathtub caulk, but that was not opaque enough to get a 20M off resistance. Use about 1/8" of black modeling clay instead. The idea is to seal out external light from the photoresistors. You can check how good a job you did by powering up the LED and looking for light leaks. Cover leaks with more black modeling clay (Sculpey).

Table of resistance versus LED current

LDR1 is at top across from LED. LDR2-5 are on sides of LED.
As would be expected, resistance curves do not track, but generate their own functions.
For use as a patching element, the important part is that all LDRs be high resistance with LED off and low resistance with LED fully on.
This seems to work OK with off resistance more than 20M and on resistance around 2K or less for all 5 LDRs

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