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

Get The Design Files

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License Info

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