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Blinkenbrain

A mouse brain pendant with chaotic tendencies. It implements a variant of the circuit described in

Simple Two-Transistor Single-Supply Resistor–Capacitor Chaotic Oscillator
Lars Keuninckx, Guy Van der Sande, and Jan Danckaert
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: EXPRESS BRIEFS, VOL. 62, NO. 9, SEPTEMBER 2015

and uses its strange dynamics to blink a blinkenlight.

Blinkenbrain rev. A

How does it blink?

Chaotic circuit schematic

The circuit consists of a RC phase shift oscillator (blue) combined with what amounts to a tunable Schmitt trigger (red). The position of the trimpot (RV1) determines if the effect of the Schmitt trigger on the oscillator.

  • When the wiper of RV1 is tuned to 0Ω, Q1B does not conduct, and the Schmitt trigger is effectively removed from the circuit
  • When the wiper of RV1 is tuned to 100kΩ, Q1B acts as trigger without hysteresis, and therefore conducts in synchrony with the RC oscillator.
  • When the wiper of RV1 is turned in between these two extremes, a hysteretic path is formed between Q1B's conducting and non-conducting states, which results in the emergence of two interacting unstable equilibria and, for some values of RV1, chaotic dynamics.

The gate of an N-channel MOSFET is tied to the collector of Q1A to drive the LED without influencing the circuit's dynamics. The following image shows VTP4 vs.VTP3 when RV1 is tuned to ~70kΩ.

V(TP4) vs. V(TP3) when RV1 is tuned to ~70kΩ

License

"No Rights Reserved", CC0