Here's another decade counter using a counter IC, but this one is an up counter unlike the one we built in our last project. It can display the numbers 0 - 9 by four LEDs.
Figure 1 shows the decimal number for each of the counter outputs displayed by different ON-OFF combinations of the four LEDs.
The schematic shows you that IC 74HC191 is the decade up counter, and S1 sends the pulses to the CK terminal. The output of the counter is taken from Q0 - Q3.
When you finish assembling, turn power ON and press S1.
The counter starts counting the numbers upward from 0 to 1, 2,3, 4 ... and so on. Use this project while looking at Figure 1 so you can get a better understanding of the counter operation.