Digital Clock

[Sangharsh Sharma]

Hello guys...I'm making a digital clock using ics 7490, 7447 and seven segment display. It's for my college project.I'm confused actually on how to take a input clock signal in 7490 ic. I've completed the seconds counter portion. But I'm confused about the minutes portion regarding how to take input clock on 7490 ic from output of previous 7490(seconds counter). Could you help me with this? I wanted to know how each output pin of 7490 ic functions and how do we differentiate which output pin is to be used for sending clock to another 7490? Hope you got the question...I've attached the schematic for two second counters and a minute counter below...would appreciate your help..

[StillTrying]

U2's Q2, (10s of the seconds) clocks U5 (1s of the minutes).

[johnkenyon]

Hint: You want the minutes counter to increment when the seconds count gets to 60.

Look at the function of the AND gate U4A in your 00-59 seconds counter.

Think about what happens when the count is at "5" (0101) and when it goes to "6" (0110).

When the output of the AND gate goes to "1" what does it indicate, and what effect does it have on the "tens" counter?

[Sangharsh Sharma]

Yes, I have done that part...actually in the seconds portion, we gotta take the clock input from 11 pin...but in minute portion we take it from pin 8...why??

[StillTrying]

"actually in the seconds portion, we gotta take the clock input from 11 pin...but in minute portion we take it from pin 8...why??"

Q3 represents the decimal value '8'. The 10s of seconds and 10s of minutes never count up to the value '8' because they're reset to 0 when they reach the value '6', so you have use the previous output Q2, for acounter that only goes 0 to 5, obvious surely!

http://genderi.org/tutorial-of-frequency-division.html#Decade_Counter_Timing_Diagram

[Wimberleytech]

Wow, this takes me back.  I designed one and built two of them back in 1975.  Here are the schematics.

[PA0PBZ]