Musical Tempo Generator
Here's the operational amplifier version of the electronic metronome from Project (Electronic Metronome).
Slide the switch to position OFF, and connect the wires carefully-this project is much more complicated than most of the others.
When you finish assembling the circuit, set the control to the 12 o'clock position and slide the switch to position ON to turn on the power.
You'll hear a pip sound from the speaker at fixed intervals. Now slowly rotate the control clockwise, and the beats come faster. Now take a look at the schematic.
IC 1 and IC 2 are used as astable multivibrators, as in our project First Aid Siren. But you'll notice that IC 1 uses diodes to generate short pulses and the control is used to adjust the speed of the pulses. The transistor turns on each time a pulse is generated, and produces a sound.