Shift register
Électronique / Electronic
7400, 7476

What's a shift register? If you've used a hand-held electronic calculator, you've already seen one in action.

This Project is a simple shift register that will let you discover how the circuit works. There's a lot of connections to be made in wiring this Project, so take your time and double-check youi work as you go along.

Set the Select Switch to B before turning the power ON.

When you turn power ON, and press the Key several times, you'll see that both LED 1 and LED 2 are off.

Now move the Select Switch to A and press the Key once. LED 1 will light.

Now press the Key and again and LED 2 will light as well. Both will stay lit no matter how many more times you press the Key.

Now set the Select Switch to B and press the Key once. What happens?

Press the Key again. Is there any change? Keep pressing the Key a few more times and see if anything else happens.

A shift register is a circuit used to store information by shifting it from one flip-flop to another. You saw this shifting take place as you pressed the Key and the LEDs lit or went off.

In calculators, a more complex version of this circuit causes the number "10" to appear on the calculator display when you add 1 to 9.