I will please like to know how i can connect to decade counters together, so instead of me having 10 ouputs i have 20. and also it shouldn't be counting at d same time. Thanks

 

What decade counter ICs are you using in your design?

hgmjr

 

Do you mean like a 5-stage Johnson counter, as in a CD4017B or 74HC4017?

If so, look at OnSemi's datasheet for a MC14017. You don't get 20 outputs when they're cascaded; you get 9 outputs from the 1st counter, and 8 each from any subsequent counter. That's because the last output is used to enable the count of the next-in-line counter. You can't use the 1st output in the 2nd through the last counters, because that output will be high until it receives it's first clock.

I've attached just the circuits for cascading 2 and 3 4017's.