up-down counter 74191 using push button

Thread Starter

nasimimtiaz

Joined Sep 19, 2011
1
hi,
i need to use two push button with up-down counter 74191. PRESSING one push button will count one digit UP and PRESSING the other one will count one digit DOWN.

I read the datasheet. But i am not understanding it. i am attaching a figure can anyone give me a clue how to connect it. i know i need to use push-up or pull down resistors to prevent floating point....but the idea is not clear to me.....pls help
 

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SgtWookie

Joined Jul 17, 2007
22,210
It doesn't work like that.

The 74191 has an up/down select input, and a clock input. Every time you get a clock input, it counts in the direction of the up/down select input.

Here, the pulser is a clock source:


Is this a homework assignment?
 

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elec_mech

Joined Nov 12, 2008
1,500
As SgtWookie asked, is this a homework assignment?

Do you have to use this particular IC or can you use another?

In addition to having a single clock input and a select up/down input, note this IC is a binary counter. This means it will count from 0-15, not 0-9. Therefore, you're going to see some interesting things on the display from 10 to 15 - see the datasheet for the 74LS47, it will show you.

If you only want to count from 0 to 9 and not 0 - 15, then you need a decade counter, not a binary counter. Take another look at the 74LS191 datasheet, it should also list another IC - one with a decade counter.
 
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