Hi, I need some help to design what sounds like a simple project. All it needs to do is count up or down (displaying on 7 segment displays) when a button is pressed. I have been trying to use Ic's SN74192 as the counter and SN74247 as the display driver. It only need to be up to 99.

As well as this I also want to have another display that counts down (MM:SS) from 2 minutes. Once it has counted down to zero, then it resets to blank state or just stays at zero.

Any help here would be much appreciated.

Thanks, Dazed & Confused

 

How about posting your circuit design so far. This will give the members a starting point in assisting you with your design.

hgmjr

 

That's 99 hex, not decimal, right? Converting hex to BCD takes a lot more than two chips...

 

The 74192 is a presettable Up/Down BCD counter, so 2 of them cascaded (carry goes to Clock Up, Borrow goes to clock down pin 12#1 to 5#2, pin 13#1 to pin 4#2) should count to 99 and back.
http://www.hcc.hawaii.edu/~richardi/113/c113_3d/3d_4/3d4.htm

 

How about posting your circuit design so far. This will give the members a starting point in assisting you with your design.

hgmjr

Thanks Hgmjr, I have started by trying to get one 7 segemnt display working as I under stand the cascading to add more on. I have attached a jpeg of my little mess.

Thanks

 

The LOAD signal has no source, it is not driven, neither is it pulled up or down (this also affects the NAND gate inputs).

Also, the CLEAR and preset lines A-D need to be terminated appropriately.

ALWAYS terminate any unused inputs to the appropriate state.

 

Ok, Thanks. Now what does that mean? Sorry I am very new to this. Are you able to edit the jpg? or sketch it si I can see what you mean. Thanks

 

See attached:

 

Thanks sooo much. You have been a huge help & a lot of progress has been made.

Thanks Again

Aaron