Meet the VCO
VCO?? What's that???
"VCO" is short for "voltage controlled oscillator."
The name alone should give you a big hint how this Project will work. When you finish wiring this circuit, turn power ON.
Select the 1.5V. What kind of sound do you hear through the Earphone?
Now Select the 4V. Do you still hear the same sound?
Select the 6V. What effect, if any, does changing the voltage have upon the sound you hear?
This Project uses the familiar astable multivibrator that we've used in many of our other Projects. The frequency of other types of oscillators is sensitive to changes in voltage as well.
VCO circuits have a variety of uses. They can let you hear when the voltage from a circuit or power source changes. They can warn when the voltage from a source gets too high or too low. And they are often found in electronic musical instruments and devices.
Try to think of some other applications for VCO circuits. You might also want to substitute the Meter or an LED in place of the Earphone to "see" what you've been hearing.