Counter that counts from 99 to 00 with start/pause button.

p3triix

Joined May 12, 2021
43
Hi, this is the first time that i'm using this forum, i need some help with a school project that is basically a counter that counts from 99 to 00, but i need to control both digits using 2 push button, until there i did everything without problem, but the main problem is that i don't know how to add the start/pause button in my circuit, i would like to know if someone can help me, i'm using the IC 74ls192 to control the digits of the 7 segments display and i'm using the 74ls47 to connect it to display (the pin 11 is not doing anything for now), also when the counter hits 00 he must stop without restarting itself.

MrChips

Joined Oct 2, 2009
23,536
Welcome to AAC!

RUN/STOP are two separate logic states.
You can control and store logic states with flip-flops. Try learning how a J-K flip-flop works.

p3triix

Joined May 12, 2021
43
Welcome to AAC!

RUN/STOP are two separate logic states.
You can control and store logic states with flip-flops. Try learning how a J-K flip-flop works.
i tried to use that but i don't really get how i could connect the 74ls192 into a J-K flip-flop, i checked the datasheet but it didn't help alot

MrChips

Joined Oct 2, 2009
23,536
Logic gates are called "gates" for a logical reason. They control the flow of digital data through the gate.

Draw the truth-table of a 2-input AND gate.
Inputs are labelled A and B. Output is labelled F.
The boolean equation of an AND gate can be written as:
F = A AND B
or
F = A.B

Learn how A can control the flow of B using an AND gate.
Inversely, learn how B can control the flow of A.

p3triix

Joined May 12, 2021
43
Logic gates are called "gates" for a logical reason. They control the flow of digital data through the gate.

Draw the truth-table of a 2-input AND gate.
Inputs are labelled A and B. Output is labelled F.
The boolean equation of an AND gate can be written as:
F = A AND B
or
F = A.B

Learn how A can control the flow of B using an AND gate.
Inversely, learn how B can control the flow of A.
so basically after all the connections in the clock I need to somehow find a way to make the condidition of an AND gate works, so the output of the AND gate i have to connect in my IC to make my project works ?

MrChips

Joined Oct 2, 2009
23,536
A counter needs a CLOCK signal in order to go from one state to the next. If no CLOCK is present the counter does not change state.

Use a 2-input AND gate to control the flow of the CLOCK.

p3triix

Joined May 12, 2021
43
A counter needs a CLOCK signal in order to go from one state to the next. If no CLOCK is present the counter does not change state.

Use a 2-input AND gate to control the flow of the CLOCK.
i already did that once, but my main doubt is where do i connect the output from AND

ericgibbs

Joined Jan 29, 2010
12,932
hi,
The output from the AND is the clock.
E

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p3triix

Joined May 12, 2021
43
hi,
The output from the AND is the clock.
E
i still have another doubt, how do i make 74ls192/74ls193 stop at 0 without restarting ?

p3triix

Joined May 12, 2021
43
Welcome to AAC!

RUN/STOP are two separate logic states.
You can control and store logic states with flip-flops. Try learning how a J-K flip-flop works.
the main problem is that the condition is that both run and stop/pause must be the same button.

dl324

Joined Mar 30, 2015
12,871
this is the first time that i'm using this forum
Most of us prefer schematics to wiring diagrams.

Show us a schematic of your attempts at implementing start/pause.

djsfantasi

Joined Apr 11, 2010
7,693
i still have another doubt, how do i make 74ls192/74ls193 stop at 0 without restarting ?
Use a 2-input AND gate to control the flow of the CLOCK.

p3triix

Joined May 12, 2021
43
my english is kinda bad sorry, what exactly would be the flow ?

MrChips

Joined Oct 2, 2009
23,536
the main problem is that the condition is that both run and stop/pause must be the same button.
That is not a problem. It is a very common mode of operation and implementation.
You have to learn how to do this. It is at a basic level of understanding digital circuitry, same as how to use gates.

Do you know how to apply an AND gate in a digital design?

djsfantasi

Joined Apr 11, 2010
7,693
my english is kinda bad sorry, what exactly would be the flow ?
Prevent the clock from going / flowing to the counter chip.

ericgibbs

Joined Jan 29, 2010
12,932
hi p3,
Use the TC output pins for stop at Zero count, add a little logic to flip the JK state

E

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MrChips

Joined Oct 2, 2009
23,536
Practical application of logic gates

ericgibbs

Joined Jan 29, 2010
12,932
hi p3,
Did you use a JK Bistable to control the Clock into the 74192.?

E

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MrChips

Joined Oct 2, 2009
23,536
Practical application of logic gates

This is called a gate valve. Have you ever seen or used one like this?

p3triix

Joined May 12, 2021
43
Most of us prefer schematics to wiring diagrams.

Show us a schematic of your attempts at implementing start/pause.
i'm sorry that it's look like that ugly because i'm not very good at drawing, but this is what i have for now with my project, i can make it count down automatically, but i need to use a button to do that, and it also restart to 99 instead finish to 00 (also there is no resistor because the program that i'm using to build that don't need it)