I wanted a counter that would basically count from a input signal, such as a reed relay to count the turns when winding a transformer or inductor for example. so I came up with this. I limited it to 3 digits (so it counts up to 999) because I only had veroboard big enough for that many but technically I don't think there is a limit to how many you can cascade because the CD4026 basically counts to 9 and sends out a clock signal on ten to the CLK in on the next chip
quite a simple circuit in theory but a pain in the arse with the jumpers and stuff, in order to try and save space I made jumper rails with little wire hooks which I've drawn on a little post-it note to try to show you what I mean, though I do tend to put the jumper a lot closer to the board than the diagram shows of course!
while building this up, I came across the issue where if I touched it, it would start counting up rapidally - this was because my body was acting as an antenna for 60Hz mains hum which can be an issue sometimes so I added a little R C bit to stop this and this also served to make it reliable when using a push-to-make switch to count on it.
if you want the exact LED displays I used it was this one LED DISPLAY but any common cathode display will do as long as the pinout is the same (shown below