I'm a very beginner in electronics...Here's my circuit... I have made last three digits of HH:MM:SS clock but the minute SSD(shown) is not working on my simulator...
Please I need help....
Duffy,
To enable count, i've set CE low...same is in IC1...there it works
And what is OE? I didn't get you...
Actually my problem is that, when the terminals A,B,C goes low, this must give an o/p high. and this high is fed into clk if IC3.....While simulating the o/p comes as high as expected but clk shows 0.....
Ya i've removed the ground from EO now.....but not working still now...Is my logic right? ....Please suggest some alternatives for a digital clock using 4000 series ICs
I've not thought of circuit further than this..This pic shows two second SSDs and one minute SSD..
I am trying to reset the mid SSD's counter when its value is 6...............
Please Help me people.... And i am unnown of further circuits as well
You are combining TTL with Cmos logic. But the minimum TTL logic high output voltage is not high enough for a Cmos minimum logic high input voltage according to Don Lancaster in his Cmos Cookbook. He suggests adding a 2.2k pullup resistor to make the logic high output voltage from the TTL output high enough.
But your Simulator program probably doesn't know these things.
oh oh.....is that the problem..... thanks brother....i actually didn't knew about pull up resistors........
can you show a demo circuit to use pullup in my circuit........
Is it like switch?......which will be On when cmos o/p CLK is on and provides TTL sufficiently high valued trigger...?
TTL logic ICs operate only with a +5.0V supply.
The minimum output high voltage of a TTL gate is +2.4V and is +2.7V for an LS-TTL gate.
The minimum input high voltage of a Cmos gate is +3.5V.
So the voltage must be higher for it to be recognized as a valid logic high voltage.
The 2.2k pullup resistor "pulls up" the voltage because it is connected to the +5.0V supply.
It is shown here:
thanks brother it's working now.........
My clock is now complete upto MM:SS.....
For the HH part i've not thought yet.....
If any problem, i'll be back here....
Thanks again