Counter Wall 7 Segment Circuit Diagram
1. All pulses to be counted are to be TTL compatible. They should not exeed 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.