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[SOLVED] help needed in clock using 4026

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avirajose

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hai,
I am designing a stop watch with 4 7- segment display that couts upto 99mins or 99 sec according to the clock. I used 4 4026 and a 7408 AND gate to detect 60.

My problem is, i can't detect digit "6". I used f,e pair and e,c pair to detect 6 but my work was in vain. F,e pair detects the digit "6" but 7408 gives two adjacent pulses that the counter increments by 2.
please go through my thread....as my project has a fast approaching dead-line.

thanks in advance....
 

The issue is not clearly described it seems. It would be nice if can support the information with some schematic and further details.
 



The circuit diagram is attached. the circuit diagram is as shown in the figure.
As i mentioned above, my problem is i cant detect the digit"6" from the counter. my problem is with 7408 it gives two adjacent pulses while the input changes from 01 to 11.
 

Ok, you want to detect the transition from "5" to "6" on the 4026 output, as the only difference in displaying those numbers "e" segment = ON. But also you need to consider the same combination of the segments are used for displaying "0" and "8". :-|

TTL output thresholds are inconsistent with 74HC, 74C and 40' CMOS inputs, to solve the problems use a pull-up 2.2k resistor to 5 V on the 7408 output.

Anyway, this does not solve counting by "60" on the first two digits, you need also to reset counters and to eliminate the false pulse for displaying the "0" by adding the segment "g" in same equation ( need to use a 3 input AND gate instead of 2 input AND gate)
 
hai,
That was awesome. It works fine .I used the 3 input and gate with f,g,e as inputs. Detecting digit "8"was not under consideration since the counter was reset at 6 itself and also since i used separate counters for each digit.

Again thanking all for ur valuable time..
 

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