GMU:Bioelectronics, aesthetics and other interesting things/PhyChip synthesiser

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Performance / Video documentation

Live performance at ACUD, Berlin, 27 Aug 2015

List of videos:

Full sonification output:

PhyChip Synthesiser

PhyChip Synthesiser is developed by Leslie Garcia and Paloma Lopez (interspecifics) within the PhiChip project for the analysis of physarum polycephalum. According to Leslie, the synthesiser could also be used for the analysis of bacteria activity within a microbial fuel cell.

Along the synthesiser we have a couple of circuits, a number of documented performances and a description of inoculated physarum polycefalum to be used within the setting. Our task is to understand how the synthesiser functions.

Terms and labels found along the provided documentation

  • VC/VCO, voltage-controlled oscillator is "an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, modulating signals applied to control input may cause frequency modulation (FM) or phase modulation (PM)" (wikipedia A). Within the PhyChip Synthesiser, the VCO is given to physarum polycephalum, whose resistance varies between 1300-1500 Ohm/cm. Within the analog part pf the modular there are three main components integrated, two of which are designed using the CD4584 Schmitt trigger. The oscillators are based on Nicolas Collins work (Collins 2009).
  • "In electronics, a Schmitt trigger is a comparator circuit with hysteresis implemented by applying positive feedback to the noninverting input of a comparator or differential amplifier. It is an active circuit which converts an analog input signal to a digital output signal. The circuit is named a 'trigger' because the output retains its value until the input changes sufficiently to trigger a change" (wikipedia B).
  • CASCADE module: frequency divider. a circuit that takes an input signal of a frequency and generates an output signal of a frequency: f(out)=f(in)/n where n is is an integer. Within the modul the integer is 2, 4, 8, 16, 32, 64, 128, 256, 512, and 1024.
  • CELL-AMP module is an arduino-type transducer converting analog signal into serial.
  • PWM or Pulse-width modulation is a modulation technique used to encode a message into a pulsing signal, eg for getting analog results with digital means. "Digital control is used to create a square wave, a signal switched between on and off. This on-off pattern can simulate voltages in between full on (5 Volts) and off (0 Volts) by changing the portion of the time the signal spends on versus the time that the signal spends off. The duration of "on time" is called the pulse width" (arduino).

Physarum plates

Utilised coated 35 mm petri dishes in a 3 row x 2 column arrangement. Every plate was treated with an aluminium mesh with a resistance of 0.5 Ω-cm. The mesh is separated by the plate walls. In front of each cell a 4 x 3 mm aluminium finger was placed to create the contact areas. Physarum resistance was around 1300-1500 Ω·cm. On top of each plate added a 3 mm agar 2% concentration for placing the physarum.

Hacking the Circadia module