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2minute countdown timer help using 74190N

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Leghrand DeJesus

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Hi! Can anyone here help me about my problem? I already had my circuit diagram which displays 2:00 at start up. The problem is, the digits will count
(for2)
2 1 0 9 8 7 6 5 4 3 2 1 0 9 8.....and so on. When it reaches 0, the 0 digit beside the 2 becomes 9 8 7 6 5 4 3 2 1 0 then 9 8 7...... again. the same thing applied to the last zero digit. Capture.JPG

you know, I want for my circuit is to be a real count down timer. Please help me. Thanks.

Here's my schem...
 

You want the tens column to go directly from 0 to 5.

The simple way to do this is by loading binary '0101' into the 74190 inputs whenever it receives an underflow signal from the ones column.
 
BradtheRad said:
You want the tens column to go directly from 0 to 5.

The simple way to do this is by loading binary '0101' into the 74190 inputs whenever it receives an underflow signal from the ones column.
Click to expand...




THank you for that. But how would I do that?

- - - Updated - - -

How will I load binary '0101' into the 74190 inputs whenever it receives an underflow signal from the ones column. thanks for the help . :)
 

I spoke too soon. It should be triggered by an underflow in the tens column.
Or it should be triggered by the occurrence of a 9 (binary 1001) in the tens column.
Or maybe a '0', then you must add some kind of delay.

Expect to need a logic gate or two. To achieve a delay, can be done with the help of a capacitor, plus a resistor plus a logic gate.

To load '0101', you would connect each 'data load' pin to either the supply or ground terminal. The value will be loaded when the trigger signal is applied to a particular pin on the 74190.

Here is a thread in another message board, discussing the problem. Similar threads are listed at the bottom of the page.

https://www.electro-tech-online.com/threads/74190-up-down-decade-counter-help.38104/
 

BradtheRad said:
I spoke too soon. It should be triggered by an underflow in the tens column.
Or it should be triggered by the occurrence of a 9 (binary 1001) in the tens column.
Or maybe a '0', then you must add some kind of delay.

Expect to need a logic gate or two. To achieve a delay, can be done with the help of a capacitor, plus a resistor plus a logic gate.

To load '0101', you would connect each 'data load' pin to either the supply or ground terminal. The value will be loaded when the trigger signal is applied to a particular pin on the 74190.

Here is a thread in another message board, discussing the problem. Similar threads are listed at the bottom of the page.

https://www.electro-tech-online.com/threads/74190-up-down-decade-counter-help.38104/
Click to expand...



Do you mean sir that I should used an NE555 timer?
 

Not sure if it requires a 555 timer, although that may be one way to do the job.

I have not personally worked to solve this challenge.
I know the goal is to detect a 9, or detect an underflow pulse...
and then to make the IC contain a 5, and do it in the time window before the 9 is seen.

With clock/timer projects being popular as they are, we would hope the IC designers would have made the task easy.

Yet you can see from discussions, it will require more work and parts and board space.

Perhaps some expert here can add his knowledge and experience?
 

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