LED and Lamp Flasher and Metronome

All these circuits are oscillator circuits (astable multivibrators). In the LED flasher circuit, a transistor is used to amplify the 555’s output in order to provide sufficient current to drive the LED, while RS is used to prevent excessive current from damaging the LED. In the lamp-flasher circuit, a MOSFET amplifier is used to control current flow through the lamp. A power MOSFET may be needed if the lamp draws a considerable amount of current.

The metronome circuit produces a series of “clicks” at a rate determined by R2. To control the volume of the clicks, R4 can be adjusted.