Digital clock without using micro-controller
by Yasir Iqbal
Digital clock made by ICS including dual BCD counter 4518ic, BCD decoder 7447/48 and gate ic 7408. This clock is simple, first counter take input clock of 1 second which is producing from 555 timer ic and second shows in 7 segments. After 59 second it reset and adds 1 to minutes and after 60 minutes it reset and adds 1 to hour section as you can see in circuit diagram.
The 555 timer ic generate pulse of 1 second and it trigger to counter ic whenever pulse given counter counts forward and give output of 4 bit which further connected to BCD decoder ic and 7 segment shows the counter value. When 9 pulse completed (9 sec) and gate is connected to pin 14 and 11 of cd4518 counter ic which trigger the second counter that further connected to 7447/48 BCD decoder and 7 segment, in this way 60 second when completed, and gate is connected to pin 4 and 5 of CD 4518 counter ic , this dual counter reset and trigger the another counter for minutes purpose and when 60 minutes completed counter reset and trigger to another counter for hours purpose. In this way the whole circuit is running.
I set the pin configuration of CD 4518 according to this:
Circuit diagram of Digital clock without using micro-controller
Circuit diagram 555 timer IC
- Cd4518 (BCD dual counter) 3
- 7447/48 BCD decoder 6
- 7 segment (anode/cathode) 6
- 7408 (and gate) 3
- Resistor 470 ohm 42
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