Hi to all the members,
I want to use 2 decade counters (cd4017) to drive 20 led's. I don't have a schematic so far to show you because i first want to know the details.Do i take the carry out from ic1 straight to the clock input of ic2, or do i need to use a nand gate to invert the output signal. The next question is, after i connect ic1 with ic2, what do i do with the reset pin of ic1.Do i still take it to ground. I want the 20 led's to count from 1-20
If it's possible for anyone to show me a schematic how exactly to do this, I'll appreciate it.

Thanks for your help

 

Two decade counters will give a BCD count. Something similar to:

0000 0000
0000 0001
0000 0010
...
1001 0111
1001 1000
1001 1001
0000 0000

It will have a 100 permutations, then cycle over. Somehow I don't think this is what you want.

Have you read this?

LEDs, 555s, Flashers, and Light Chasers

 

The 4017 is a Johnson counter. Two in series will crank out 20 states.

To the OP - the data sheet shows how to cascade them - http://focus.ti.com/general/docs/li...nericPartNumber=cd4017b&fileType=pdf&track=no

 

Opps, and the 4017 is a mainstay in the link I suggested.

 

Bill, i know how to use the cd4017 in a single stage with 10 led's. Thought, i have my own cmos data book. The data sheet show me how to use more than one cd4017 in one diagram, but it's for a 8 decoded outputs I want to use two cd4017 ic's with 20 outputs, if it's possible and then i want you to show me what output of the first ic go to clock of the next ic
I visit your page more times than you can think. there's a lot of grate stuff. Many thanks for all the afford you put into that site. I learned mush more about the lm555 timer on your site than i learned ever before.

 

I am not sure you can cascade 2 4017's to get 20 separate outputs, since when the 4017 is reset output 0 will always be high on both IC's, so on power up you will always have atleast 2 LED's lit..... and to cascade 2 of the 4017's you will not get the sequence you want since you will have to clock the first IC 11 times before the second one will increment..... so at most you will be able to connect 18 LED's to 2 4017's and figure out a way to stop the clock input to the first one when clocking the second IC and vise-versa...

B. Morse

 

Hello,

How about this thread:
http://forum.allaboutcircuits.com/showthread.php?t=38621

Bertus

 

BMorse, many thanks for the help. What you said is just what i wanted to hear, and that was if can or cannot do it the way i wanted to do it. I'm gonna use the diagram in the thread Bertus show me.
Thanks again for all the help guys.