Digital Clock using 7490 (RESET Button) HELP!

Thread Starter

nephelem

Joined Jan 24, 2016
20
I am working on a 24-Hour Digital Clock project with 7490/74ls90 as my BCD. It should have three buttons. 1.) Hour - Increment button. 2.) Minute - Increment button 3.) RESET button. I am not sure if my schematic is correct but it works okay. The two increment buttons are working but I don't know how to connect the RESET to reset all the 7 segment LEDs to 00 00 00.

It's my first time working with this kind of ICs. My knowledge on cascading these counters came from the book about digital electronics by A. P. Godse which I have read few days ago and by searching through internet. So you could really say I'm a noob. We were just instructed by our professor to use a 74192/74ls192 or 7490/74ls90. Btw, I have another thread similar to this except I used 74192 (http://forum.allaboutcircuits.com/threads/digital-clock-using-74192-reset-button-help.120129/).

Can you please help me? Better if you include a schematic/circuit diagram so I could understand.
Thank you very much. Attached here is my schematic:what2.jpg
 

dl324

Joined Mar 30, 2015
11,009
If this is a school project for which you will receive a grade, you should have your post moved to the Homework Help forum. In the Projects forum, someone might just give you the answers and that could be considered cheating; and I've read that some professors visit this forum...

Think about what you want reset to do and what you're attempting to do. Do you want reset to display zeros on the display or do you want to reset the counters?
 

Thread Starter

nephelem

Joined Jan 24, 2016
20
If this is a school project for which you will receive a grade, you should have your post moved to the Homework Help forum. In the Projects forum, someone might just give you the answers and that could be considered cheating; and I've read that some professors visit this forum...

Think about what you want reset to do and what you're attempting to do. Do you want reset to display zeros on the display or do you want to reset the counters?
what i mean is all the counters will clear/ start again from 00 00 00 when i press the button.
 
Last edited:

dl324

Joined Mar 30, 2015
11,009
lol don't worry about it. i don't think my professor would just sign up here just to spy. regardless of how you do it, what matters to him is the final result which is the hardware/prototype itself. here in my country, project is different from homework. it is MORE than homework.
But I do worry about it. It would be unethical for someone to help you cheat on school work.
what i mean is all the counters will clear/ start again from 00 00 00 when i press the button.
Will the circuit that you've started accomplish that?
 
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Thread Starter

nephelem

Joined Jan 24, 2016
20
But I do worry about it. It would be unethical for someone to help you cheat on school work.
Will the circuit that you've started accomplish that?
But I do worry about it. It would be unethical for someone to help you cheat on school work.
Will the circuit that you've started accomplish that?
well, i think so? i'm close but not really sure..
 

dl324

Joined Mar 30, 2015
11,009
You have BL, BI, and LT tied directly to the power supply; all are low active. What will happen if you try to pull them low? Would that reset the corresponding counter?
 

dl324

Joined Mar 30, 2015
11,009
The OP deleted their first post so my post was promoted to TS??

I don't need help, so don't ask me to post a schematic...
 

Thread Starter

nephelem

Joined Jan 24, 2016
20
I'm the OP but the admin moved my thread to the other forum. What does TS mean? Or is that reply meant to other thread? wrong post?
 

dl324

Joined Mar 30, 2015
11,009
You have BL, BI, and LT tied directly to the power supply; all are low active. What will happen if you try to pull them low? Would that reset the corresponding counter?
Answer my questions and we can continue working on your circuit while waiting for the two threads to be merged.
 
Last edited:

hp1729

Joined Nov 23, 2015
2,304
[SIZE=4][URL='https://forum.allaboutcircuits.com/members/nephelem.314509/']nephelem[/URL][/SIZE] post: 957754 said:
I am working on a 24-Hour Digital Clock project with 7490/74ls90 as my BCD. It should have three buttons. 1.) Hour - Increment button. 2.) Minute - Increment button 3.) RESET button. I am not sure if my schematic is correct but it works okay. The two increment buttons are working but I don't know how to connect the RESET to reset all the 7 segment LEDs to 00 00 00.

It's my first time working with this kind of ICs. My knowledge on cascading these counters came from the book about digital electronics by A. P. Godse which I have read few days ago and by searching through internet. So you could really say I'm a noob. We were just instructed by our professor to use a 74192/74ls192 or 7490/74ls90. Btw, I have another thread similar to this except I used 74192 (http://forum.allaboutcircuits.com/threads/digital-clock-using-74192-reset-button-help.120129/).

Can you please help me? Better if you include a schematic/circuit diagram so I could understand.
Thank you very much. Attached here is my schematic:View attachment 99565
On those 7-segment displays ... do you think one resistor for the whole display is correct? If only one LED at a time were on that would work. But ...

Clock inputs are low edge clocks? Take a look at your pushbuttons.

Have you considered building these circuits?
 
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