Optical tremolo

Among the many cool projects I saw on MakeZine, one caught my attention as a possible cool gift for dad, who is a great guitar player. It’s called the Optical Tremolo Box and it’s a tremolo effect for the guitar, which looks very interesting because it has a motor and rotates a semi-transparent disk between an LED and a light-sensitive resistor.

The first version of the effect seemed too simplistic and ineffective. There is also a second version, as if too complicated. So I decided to do something intermediate: in the first version model, I replaced the potentiometer that regulates the motor speed with a circuit that drives the motor with PWM (pulse width modulation), made with the integrated 555. Quite simple and effective, because it reduces current consumption (important, considering that the device is powered by batteries) and allows better control of the engine (at least theoretically).