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Sentry Gun - Automatic Optical Theremin Musical Instrument

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This is NOT a toy, only for ages over 15.

The Sentry Gun is a battery powered automatic optical theremin. It is improves on simple optical theremin designs by allowing the user to play the unit one handed without having it sound continually by turning on when their hand is near and stopping when it is not.

It has 2 light sensors. 1 determines the pitch of the sound and the other determines if the unit sounds or not depending on how much light falls upon it. The sensitivity of this can be altered by using the knob on the side. If the knob is turned fully clockwise it will run constantly.

The Sentry Gun has a power switch on the outside and a power LED visible through the clear plastic box. The device also has an internal switch to change the waveform between square and triangle, an internal switch to change the pitch range from high to low (low is useful in bright day light) and an internal switch to set the device to output on either the left channel only or both right and left channels. This is to make it compatible with both stereo and mono mini jack cables.

Copy this link into your browser for a demo:


It is powered by a single 9v battery (Not included). The output is via a 3.5 mm socket at line out level. Please note this is not a headphone socket, you will need something suitable to amplify the output e.g. a stereo with aux in, computer speakers, a soundcard input etc.

It measures 10cm x 10cm x 3.5cm

Sentry Gun - Automatic Optical Theremin Musical Instrument


  • Handmade item
  • Materials: electronics, plastic box
  • Ships worldwide from United Kingdom
  • Feedback: 128 reviews
  • Favorited by: 56 people