The Synthrotek Optical Theremin is one of our wildest circuits! Two optical resistors, sensitive to light shining upon them, control both the pitch and volume of a standard 555 timer in astable mode. The result: a chaotically cool noisemaker! Two potentiometers allow for setting levels and sensitivity of both optical resistors. The circuit is simple to build and powered by either a 9V battery or a 9V center negative AC adapter. Loads of fun and highly adaptable/modifiable, you’ll see the light with the Synthrotek Optical Theremin!
Note that if you are using an AC adapter, it needs to be 9v center NEGATIVE.