ELECTRONIC METRONOME

Construction and testing is simple. Assemble the circuit on a breadboard or general-purpose PCB. Mount all the components, except S1, and temporarily connect pin 15 of IC2 to ground rail. IC1 produces an audible tick sound (tempo beat) at a fixed rate that varies as VR1 is adjusted. IC6 produces a tone that varies in pitch from about 250 Hz (about an octave below middle C) to about 2 kHz (about two octaves above middle C) as VR2 is adjusted. The counter goes through its normal eight-stage cycle and the yellow LED (LED2) flashes once for every eight flashes of the red LED (LED1).

Now connect a loudspeaker to pin 3 of NAND gate N10 through a 10 F capacitor. The circuit should produce a series of tick sound with a double-tick sound at every eighth tick sound. If this works well, remove pin 15 of IC2 from the ground rail and connect to six-way rotary switch S1. Remove the speaker and 10µF capacitor from pin 3 of N10 and connect pin 3 to an audio power amplifier. Use presets VR1 and VR2 such that turning their knobs clockwise increases the tempo and the pitch, respectively.