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# CD 4026 and 7Seg display to count button presses

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#### Pedro147

##### Newbie level 5
Hello. I was just wondering if anyone can help me with a circuit using a CD 4026 to count button presses and display them on a 7 segment display. It needs to start at zero then increment by one for each successive button press until it registers eight presses, and on the ninth press go back to zero. I am going to use this circuit to switch the clock pin on a 74HC595 Shift register, so as well as the signal from the button press incrementing the counter display it needs to be suitable for a logic input ( monostable is it ? ) Being a beginner at all this please be kind if my explanation is somewhat technically inept. I have a circuit using an Arduino, 555 timer and 7 Seg pulsing the clock pin of the shift register but I just want to use a simpler IC configuration so I can place it all in a dedicted housing. And if you are wondering why I am manually triggering a shift register it is an educational endeavour so to speak. Thanks for taking the time to read this and hopefully offer some advice, Happy New Year Pedro. :grin:

Your explanation is very clear and concise - not inept at all. I wish everyone would post their questions as clearly. Just one suggestion: it will be even better if you break up your post into paragraphs.

The problem is identifying the ninth press as a unique event. Right now I can't think of a simple way to do that with the CD4026 alone. One possible approach is to identify which combination of segments are uniquely lit for the desired number, but that involves at least 4 segments for digit 9. Decoding that will require additional logic circuits.

Another approach would be to feed the button presses to a counter in parallel with the CD4026 input. A CD4017 would be suitable. At the ninth press, the decimal 9 output of the CD4017 (pin No.11) will go high. If that output is fed back to the RESET inputs of both ICs (pin No.15 on both ICs), the count for both ICs will be reset to 0.

One thing to remember is that a mechanical switch always has contact bounce. If that's not suppressed, the counters will see each bounce as another press.

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V
Points: 2
Thanks for the prompt response Pjdd. That is a very clever solution to my problem.

I just had a look through my small but growing parts supply, and found a 74HC4017. Is that the same IC as CD 4017 ? If not I will get a CD4017 and try out your circuit.

Thanks again and happy new year Pedro.

The 74HC series of CMOS ICs are a more advanced development of the CD4000 series. For types where the last four digits are identical in the two series, the pins and the basic functions are identical. However, most 74HC ICs have a max power supply rating of 7V and are not supposed to be operated at more than 6V. Otherwise the 74HC ICs are much faster and have a lower output resistance so that they can drive higher loads.

Pedro147

### Pedro147

Points: 2

My circuit will only be operating at 5 volts so when I receive the CD 4026 IC's I will try out your circuit.
So much to learn, but thankfully there are helpful people such as yourself to help the uninitiated,

Pedro.

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