How to debounce a normally closed switch?

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jus.2ne

Joined Oct 26, 2022
5
The 74ls192 IC's up count (pin 5) needs to get logic 0 in order to count up. I'm trying to debounce the switch so that it doesn't give multiple input to the IC. I've tried this circuit that is used for normally open switches.

But my circuit uses a normally closed one. Any advice would be appreciated. :D
 

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Reloadron

Joined Jan 15, 2015
7,080
Well OK:
"The SN54/74LS192 is an UP/DOWN BCD Decade (8421) Counter and the SN54/74LS193 is an UP/DOWN MODULO-16 Binary Counter. Separate Count Up and Count Down Clocks are used and in either counting mode the circuits operate synchronously. The outputs change state synchronous with the LOW-to-HIGH transitions on the clock inputs".

If you want a 74192 to count up (Pin 5)clock is applied to pin 5 and counts will occur on leading transitional edges of the clock (logic low to high) will increment one count. Also Pin 4 the down count must be ties to VCC. If you want to count down from a preloaded number. Counting up or down the clock applied to pin 4 or 5 the unused pin is tied to VCC and the remaining pin clocked. Count up or count down the count will happen on the low to high leading transitional edge of the clock be it a switch or clock circuit. The chip will count up from or down from a preset.

I suggest you give this a read working from hardware solutions as you have to software solutions eliminating switch bounce. :)

Ron
 

MrChips

Joined Oct 2, 2009
27,686
10kΩ is too large a resistance to pullup 74LS series input.

Try using a 74HC14 Schmitt Trigger circuit to provide hysteresis.

1669901172779.png

Edit: I think the diode D1 should be turned around.
 

Picbuster

Joined Dec 2, 2013
1,040
The 74ls192 IC's up count (pin 5) needs to get logic 0 in order to count up. I'm trying to debounce the switch so that it doesn't give multiple input to the IC. I've tried this circuit that is used for normally open switches.

But my circuit uses a normally closed one. Any advice would be appreciated. :D
Solve this in software.
use interrupt and set flag.
Switch may bounce like hell but flag remains true till application does the reset.

Picbuster
 
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