I've tried to make a schematic for a 7 segment diaplay which counts up and down with 7447 and 74192 to make a pcb board but it just doesn't workk !!!

 

Welcome to AAC!

The relevant portion of the schematic:

You said 7447, but you have 7448 in the schematic. Which is it?

Your schematic would be easier to read if you arranged the components to minimize wire length and crossings. You are also missing current limit resistors for the display.

Your switches are going to need debouncing...

 

So it doesn't work. Tell us what it does and what it doesn't do.
Show us a photo of your breadboard.
If it is a pcb, show us photos of both sides of the pcb.

 

I've tried to make a schematic for a 7 segment diaplay which counts up and down with 7447 and 74192 to make a pcb board but it just doesn't workk !!!

This is like sending an e-mail to a mechanic and telling them that your car "just doesn't work" and expecting them to tell you what's wrong.

What do you mean by "it just doesn't work"? It just might help the people you want to have help from if they knew whether "doesn't work" meant that it counted in the wrong order versus sitting there in a single state versus changing states erratically versus bursts into flames. It would also be nice to know if it just doesn't work in simulation versus on a breadboard versus on an actual pcb.

 

Welcome to AAC!

The relevant portion of the schematic:
View attachment 122424
You said 7447, but you have 7448 in the schematic. Which is it?

Your schematic would be easier to read if you arranged the components to minimize wire length and crossings. You are also missing current limit resistors for the display.

Your switches are going to need debouncing...

Sorry its a 7447 wrong pic and i made a board but it doesnt start with a zero and when i use the push button it turns into 2 and stops changing

 

This is like sending an e-mail to a mechanic and telling them that your car "just doesn't work" and expecting them to tell you what's wrong.

What do you mean by "it just doesn't work"? It just might help the people you want to have help from if they knew whether "doesn't work" meant that it counted in the wrong order versus sitting there in a single state versus changing states erratically versus bursts into flames. It would also be nice to know if it just doesn't work in simulation versus on a breadboard versus on an actual pcb.

When i use the push button its just turns into 2 and stop changing both in the pcb and the bread board i thought the schematic was wrong, I've put the right schematic in an other reply .

 

So it doesn't work. Tell us what it does and what it doesn't do.
Show us a photo of your breadboard.
If it is a pcb, show us photos of both sides of the pcb.

I dont have the pcb right now but when i use the push button to go up it turns into 2 and stop changing it doesn't even start with zero. I thougt i made a wrong schematic .

 

So it doesn't work. Tell us what it does and what it doesn't do.
Show us a photo of your breadboard.
If it is a pcb, show us photos of both sides of the pcb.

It stops like this and doesn't change again

 

When wiring a 7-segment display to a 7-segment decoder-driver here is a first simple test you should always do.
Temporarily connect LAMP TEST, pin-3 of 7446/7447/7448 to GND.
All seven segments should light up and display the numeral 8.
After doing the test, return pin-3 to Vcc.

 

Without debouncing the switches, the counter can change dozens of counts with each press, depending on the construction of the switches. Also, you need decoupling capacitors for each chip.

ak

 

It stops like this and doesn't change again

74LS192 and 74LS47 chips will not run off a 9V battery directly.
You need to install a 7805 5V regulator to reduce the supply voltage to 5V.

 

With the TTL logic asymmetrical inputs, it is difficult to use pull down on the inputs, so what is the value of R8 and R9?

Worst case values for a low LS-TTL input is: 0.8 Volt / 0.4 mAmp ~ maximum 2K Ω pull down. In the photo, I can see two resistors that resemble 3K3 Ω.

 

So let me be sure I understand this: You made a PCB without first testing your design at all (since the bread boarded version behaves the same way)?

That right there is a highly valuable (and hopefully not too expensive) lesson learned!

 

So let me be sure I understand this: You made a PCB without first testing your design at all (since the bread boarded version behaves the same way)?

That right there is a highly valuable (and hopefully not too expensive) lesson learned!

I'm a beginner at this and this is just a self learning, so i need to learn a lot of things really.

 

With the TTL logic asymmetrical inputs, it is difficult to use pull down on the inputs, so what is the value of R8 and R9?

Worst case values for a low LS-TTL input is: 0.8 Volt / 0.4 mAmp ~ maximum 2Kpull down. In the photo, I can see two resistors that resemble 3K3 Ω.

They are 300 Ω

 

What type of driver and display do you have? 7447 uses common anode and resistors. 7448 uses common cathode, no resistors needed.

 

I've tried to make a schematic for a 7 segment diaplay which counts up and down with 7447 and 74192 to make a pcb board but it just doesn't workk !!!

1. I've redrawn your schematic for clarity, added debounce for the switches, ballast for the display segments, and a POR (power-on-reset) so the counter will come up on either 9 or 0. Maybe...

2. If you're using a 74LS47 for the display driver, the display must be common anode, and the anode must go
to +5 volts. You show it going to ground.

3. I've not shown it, but U1 AND U2'S unused inputs should be connected to either +5V or ground.

The latest schematic follows, and I've changed the up-down clock controls to make the 74192 happy, the POR to drive the counter's CLEAR input successfully, and the pushbutton switch interface in order to address Scott Wang's and MrChips' concerns.

 

When i use the push button its just turns into 2 and stop changing both in the pcb and the bread board i thought the schematic was wrong, I've put the right schematic in an other reply .

Here are excerpts from the TI and ON semi 'LS 192 data sheets. Note that if you want to count UP, the DOWN input must be held high while the UP input is pulsed, and if you want to count DOWN, the UP pulse must be held high while the DOWN input is pulsed.


See #17 for the implementation.

 

1. I've redrawn your schematic for clarity, added debounce for the switches, ballast for the display segments, and a POR (power-on-reset) so the counter will come up on either 9 or 0. Maybe...

2. If you're using a 74LS47 for the display driver, the display must be common anode, and the anode must go
to +5 volts. You show it going to ground.

3. I've not shown it, but U1 AND U2'S unused inputs should be connected to either +5V or ground.

The latest schematic follows, and I've changed the up-down clock controls to make the 74192 happy and the POR to drive the counter's CLEAR input successfully.
View attachment 122630

The low level for 74LSxx that the pull low resistor should be around 330Ω, if the pull low resistor too big then the input level will not reach to a stand low level, because the internal resistor and pull low resistor as a voltage divider, you can check the internal circuit of 74LSxx series ic.

 

The low level for 74LSxx that the pull low resistor should be around 330Ω, if the pull low resistor too big then the input level will not reach to a stand low level, because the internal resistor and pull low resistor as a voltage divider, you can check the internal circuit of 74LSxx series ic.

To which part of the circuit are you referring?