This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).
| R1-R7 | 7 | 470 Ohm 1/4 Watt Resistor | |
| U1 | 1 | 74LS90 TTL BCD Counter IC | 7490,74HC90 |
| U2 | 1 | 74LS47 TTL Seven Segment Display Driver IC | 7447,74HC47 |
| DISP1 | 1 | Common Anode 7 Segment LED Display | |
| MISC | 1 | Board, Sockets For ICs, Wire |
1. All pulses to be counted are to be TTL compatible. They should not exceed 5V and not fall below ground.
2. You can add more digits by building a second (or third, or fourth, etc..) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.