This musical light alarm circuit is very simple, uses only 7 components, a LDR and a 3.6 V battery or 3 x 1.2 volts rechargeable batteries. The well-known UM66 is used as the sound generator and will ...

A synthesizer without transistors could almost be the basis of a trick question, surely without transistors it must be using a vacuum tube or similar. Not [Dr. Cockroach]’s synth though, instead of ...

It normally takes two transistors to build a blinker circuit (in order to make positive feedback possible). However, you can also use a photo-resistor (LDR) that is illuminated by an LED. The feedback ...