Sound machine I
Electronic
7400

Here's another digital sound project that makes use of a circuit we've used in some earlier Projects.

Can you tell which circuit we're talking about by looking at the schematic?

While you're pondering that question, why not listen to the sound this Project makes?

Since there are many wiring connections, take your time and check your work.

When you've finished, turn the power to ON. What do you hear?

Can you explain how this sound is produced by looking at the schematic?

The two 2SC Transistors are used to make up a multivibrator circuit (did you recognize our old friend?).

But notice that we're using two NAND gates with the multivibrator (Project NAND gate showed how a NAND gate works).

The two NAND gates effect the operation of the multivibrator, whose output then goes to the audio amplifier using the 2SA Transistor. The result is the sound you hear from the Speaker.

You can change the sound this circuit makes by substituting a different value for the 100 µF capacitor.

Also try different values for the 10K resistor and 0.05 µF capacitor and see what happens.

Notice that we said we're using "two NAND gates" although all connections are being made to a single component. Does this and the name of that component give you any idea about what an Integrated Circuit is?

You might want to review the guess you made after building Project NAND gate. Have you changed your mind any since using this current Project?