Up/down counter
Électronique / Electronic
74HC02, 74HC191

Here's an up/down counter that uses a counter IC with an up/down function.

Output of this counter is displayed by four LEDs. S2 is used for up/down switching.

This counter works as an down counter when S2 is OFF, and as a up counter when S2 is ON. S1 is used to send out the pulses to count.

Wire the project and turn power ON.

S2 is OFF at this time, so the counter works as a down counter, and starts counting from 15 to 14,13,12 and so on as you send the pulses by pressing S1.

What do you think happens if you press S1 to send out the pulses while pressing S2?

You certainly can figure that out. Repeat experimenting with this counter and get the knack of it.

Figure 1 shows the decimal number for each of the counter outputs displayed by different ON-OFF combinations of LED 1 - LED 4.

Decimal Number
"1" when LED is ON
"0" when LED is OFF