How should I stop 7 segment for counting? It should be only be counting 0-8.

dl324

Joined Mar 30, 2015
9,331
Its not just simply a homework.. If I cant do this in PCB, our professor will give me 5...
I have requested that your post be moved to the Homework Help forum where you'll be guided to a solution.

What is the counter doing as wired?

What were you told to do with unused inputs?

What purpose does the 220 ohm resistor serve?

Will the BCD to seven segment decoder work as you have it wired?

The bubbles on the outputs of the decoder indicate the outputs are low active. You have the common terminal on the display connected to ground. Do you think that will work?

What were you taught about current limiting for LEDs?
 

BillB3857

Joined Feb 28, 2009
2,506
How would YOU know when the counter got to nine? What device can you think of that could generate a positive signal when it recognized nine?
What pin(s) of the 74ls90 could you use to force the count back to zero? If you answer these, you have it made.
 

Thread Starter

Tomomi Mei Manalili Reyes

Joined Feb 3, 2016
49
How would YOU know when the counter got to nine? What device can you think of that could generate a positive signal when it recognized nine?
What pin(s) of the 74ls90 could you use to force the count back to zero? If you answer these, you have it made.

I literally dont know.. Our professor gave us this task but he didnt teach us on what should we do. He told us to have an idea through internet, but i cant find any information about it.. >o< I badly need this today. I must have a layout for this to put it on photo-pcb.
 

BillB3857

Joined Feb 28, 2009
2,506
It would be impossible to lay out a PC board without first having a working circuit design. The one you posted WILL NOT do what you want. The suggestions/questions posted are to help GUIDE you into a thought process to arrive at the answer you need to make the circuit work. This forum does not do your homework for you, but will try to help. If you would even attempt to answer questions, you may get more help. Otherwise, well........
 

Papabravo

Joined Feb 24, 2006
12,695
We are sorry that your professor is such an inadequate teacher, and that your university employs such incompetent people. Maybe you should ask for a refund, or better yet don't register for the next term.
 

Thread Starter

Tomomi Mei Manalili Reyes

Joined Feb 3, 2016
49
It would be impossible to lay out a PC board without first having a working circuit design. The one you posted WILL NOT do what you want. The suggestions/questions posted are to help GUIDE you into a thought process to arrive at the answer you need to make the circuit work. This forum does not do your homework for you, but will try to help. If you would even attempt to answer questions, you may get more help. Otherwise, well........

yeah i know. that is why i need to figure i out as early as i can so i can now proceed in pcb layout.
will someone answer me if i ask questions?
 

Thread Starter

Tomomi Mei Manalili Reyes

Joined Feb 3, 2016
49
We are sorry that your professor is such an inadequate teacher, and that your university employs such incompetent people. Maybe you should ask for a refund, or better yet don't register for the next term.
You might have point. But for me, his just one of the hard paths of my dreams. So I'll never give up on him too easily.
 

Thread Starter

Tomomi Mei Manalili Reyes

Joined Feb 3, 2016
49
Good so far. So you want to reset it to zero at a count of nine?
can you explain it to me what is the function of 74ls90? Q0-Q3 are connections to A-D. CKA is the positive or power voltage.. Then what is the function of CKB and R0-R9?? O.O Does connections from Q0 and 7 to CKB is the reason why it counts to 9??
 

dl324

Joined Mar 30, 2015
9,331
yeah i know. that is why i need to figure i out as early as i can so i can now proceed in pcb layout.
will someone answer me if i ask questions?
Start by answering the questions you've been asked. Don't expect anyone to simply give you answers because you're short on time. We've seen students in that situation numerous times.

Given the amount of time you have, it's unlikely that you'll be able to complete a PCB layout. Doing that without having a working circuit is pointless.
 
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