When I saw Martin De Bie's Textilo
e-textile 555 oscillator I wondered if it could be extended to allow for body interactions with the pads using CMOS 555 timers in the spirit of the CrackleBox.
I tested this CMOS 555 breadboard version.
This informed suggested improvements to Textilo to Martin who came up with a textile layout which we used to teach during the audio workshop of e-textile Spring Break:
Alex blogged a great student perspective of this workshop.
I also brought along some PCB's which can be sewed to or pressed on Lego baseboards.
To address the need for more interaction room for the fingers I suggested to Martin to look at a radiating octagonal design. He prototyped this at the camp in copper:
Nicole Messier also picked up on this design pattern and made a 555 oscillator based FM Radio transmitter:
A walk through the schematic may be helpful.
We install a capacitor to ground (470pF) from pin 2.
Pin 6 is connected to Pin 2.
A 1Mohm pullup resistor is used on pin 4 (reset).
There is a decoupling capacitor for the speaker output (pin 3)
The diode (from battery to pin 8) is to help you not destroy the 555 timer if you install the battery backwards.
Now what makes things productively confusing is the absence of resistors in the story. These are provided by your fingers or additional LDRs or piezoresistive fabrics. The layout is designed to give you room to put fingers in the useful places for the two popular ways of making the 555 timer oscillator. One way creates square waves. The other makes controllable pulse waves. I capture these possibilities on the following schematic which has a special notation for where you add variable resistance: