Three-input OR circuit
Électronique / Electronic

Back in Project OR gate you got to see how an OR circuit works. That OR circuit only had two inputs, OR circuits can have more than just two inputs, as this Project will show you.

Before building this circuit, set the Select Switch to B.

When you finish the wiring connections, put the power on. What happens?

Press the Key. What happens now?

Turn the power OFF and set the Select Switch to A. What's the result?

Now try holding the Key down while setting both the Select Switch and the power switch to their two positions.

Try other combinations of the two Switches without pressing the Key. What do you find happening?

This Project was just our way of reminding you of how an OR circuit works, the output goes to 1 (turns on) if any or all of the inputs go to 1.

You also can see that an OR gate can have several inputs, in fact, most do.

You might want to set aside a special section in your notebook and the next several Projects. We've been using digital circuits for a long time. Now we're going to take a look at them in depth.