4 digit 7 segment CC - all digits count the same number

Ultimately I'm looking to build something that's going to count revolutions as part of a guitar pick up winder.

I've got a circuit hooked up with 4 x 4026 counters going into a 4 digit 7 segment display. I believe I have the correct linking of the chips withe carry from one going into the clock of the other. But every time I provide a clock pulse all 4 digits on the display increment by 1 rather than just the least significant.

I have the pin outputs from each of the chips going into the corresponding cathode of the 7 seg display but I just cannot get it to count more than 0 - 9.

What am I getting wrong?

This is my first question on here. I'm new to electronics and have been working at this for a few days but always run into the same problem. Really appreciate any help.

Thanks for the comments and answers so far. I've added what I hope passes for a circuit diagram...

I think I've got the clock in and carry out (/10) connected correctly and I think I've got the right outputs going into each of the common cathodes on the display. I'm not worried too much about re-setting or inhibiting the clock right now so I've put them to negative. I'm not doing anything with Pins 4 and 14.

The LED on the left is just another method of me knowing a clock pulse should be going in

• Please provide a schematic diagram. We can't make any useful suggestions unless we know how you have wired your circuit. Commented Apr 23, 2015 at 23:08
• Perhaps you are doing something inappropriate with the clock inhibit, please provide a complete schematic including unused inputs. Commented Apr 24, 2015 at 4:04
• Does your 4-digit display have separate lines for all of the segments of each digit or is this a multiplexed display? In other words, you actually have 4 separate 7-segment displays? Commented Apr 24, 2015 at 4:58

According to your schematic, you have the outputs of all counters connected in parallel, and to the anode inputs of your display. You have all cathode leads of the display grounded. This will force all digits to display the same number.

The display you have needs a multiplexed input. You will need seven 4:1 multiplexers between the counters and the display, with the segment outputs of counter 1 going to input 1 of the multiplexers, counter 2 to input 2, etc. You also need to arrange to ground one cathode lead of the display at a time, switching the mux and cathode selection in sync, so that display 1 will be enabled when the mux selects counter 1.

You have the clock running to all of the chips, and therefore they count in parallel. What you need to do is hook the clock to the clock of the first (least-significant) digit, and then the carry out from that digit goes to the clock of the next digit. And so on.

The 4026 has a 'divide by 10' output on pin 5. Connect this pin to the clock input to the next digit for each stage of the counter.

• Thanks Jim, I think this is one aspect of it I have got right. Maybe I've got them back to front or something? Commented Apr 24, 2015 at 11:58

Peter Benett has told you what your problem was but I have a better solution for a fix: simply change your display to 4 separate 7-segment displays.

The 4026 was designed to drive a single 7-segment display. There are other chips available that will directly drive a multiplexed display without all the extra glue logic that Peter mentions.

Be careful which 7-segment displays you purchase: they are available as "Common Cathode" and "Common Anode". The 4026 is designed to drive Common Cathode displays.

• Many thanks Dwayne, appreciate it. I've got a few single digit displays kicking about so I'll give that a go too Commented Apr 24, 2015 at 16:08