The EyeBall is a unique input device that is reminiscent of a Theremin, but is really so much more. It uses a photo transistor to sense varying light levels and convert them into analog and digital signals.

You can build one for less than $85

The EyeBall has two types of outputs, analog and digital which correspond to control voltages and gate signals.

Digital Outputs

  • Pulse+
  • Pulse-
  • Toggle

Analog Outputs

  • Normal
  • Inverted


  • Pulse Length From 70ms to 7sec (nominal)
  • Offset Adjusts base level of analog outputs
  • Level Adjusts the gain of the light amplifier
  • Sensitivity Adjusts the sensitivity of the photo transistor


  • Pulse Yellow LED when pulse is active
  • Toggle Green LED when Toggle output is HIGH
  • Clip+ Red LED when Normal output is at +5V or above
  • Clip- Blue LED when Normal output is at -5V or below
  • Note that when the Normal output is clipping, the Inverted output will also be clipping but at the opposite polarity.

Eurorack Spec

  • 17 HP width
  • 3 U height


Perhaps the best way to describe the EyeBall is to see it in action…

(This is an early prototype.)

Buy the Circuit Board and Front Panel

Price: $24.95

Get The Design Files

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