# Digital Alarm Clock

Discussion in 'Homework Help' started by msak671@hotmail.com, Oct 27, 2013.

1. ### msak671@hotmail.com Thread Starter New Member

Aug 4, 2013
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0
I am making Digital alarm clock, i have uploaded circuit diagram of digital clock, i want to ask that how can i make it alarm clock?
which IC should I use?

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2. ### MrChips Moderator

Oct 2, 2009
12,449
3,363
That is a lot of work and chips to make an alarm clock. The only reason one would design a clock in this manner is to learn how digital counter circuits work.

You can make a digital alarm clock with one mcu chip.

3. ### msak671@hotmail.com Thread Starter New Member

Aug 4, 2013
8
0
This is my project of Digital logic Design,
so i can not use any type of micro controller.

4. ### MrChips Moderator

Oct 2, 2009
12,449
3,363
So this is homework project. Adding an alarm feature would be extremely complicated.

You could limit the alarm to trigger on the hour only.

Apr 5, 2008
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6. ### JohnInTX Moderator

Jun 26, 2012
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You could use 74LS85 magnitude comparators that compare the BCD hours and minutes to values set on thumbwheel BCD switches to hold the alarm time. A=B is the alarm output.

The alarm time could also be the outputs of 4 more 7490's (or some BCD up/down counter) that uses buttons to count to the desired alarm time in the same manner that you set the time of day. In that case, you would need to multiplex the digit values between the alarm and time registers so that you could see the alarm setting.

7. ### WBahn Moderator

Mar 31, 2012
17,761
4,800
The brute force way would be to take two of these clocks and disable the clock signal for one of them (assuming that you can still set the time without it, which I can't tell because I can't read the schematic details well enough). Then use a quad XOR gate for each digit (or perhaps just the hourse and minutes) to compare the values on the two clocks. Combine all of the digits with NOR and you have a signal that goes HI only when the output of the two circuits match. Use that for your alarm trigger.

8. ### jocc New Member

Jan 28, 2014
1
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hey man, have u gotten solution for ur digital alarm clock design? if so please help me by attaching it. coz u know i'm on agreat confusion on it and i need a help of espeasially yours. and make it fast
THANK YOU

9. ### MrChips Moderator

Oct 2, 2009
12,449
3,363
Watch your language and tone of voice.

The purpose of AAC is to help each other learn and not to serve you on a silver platter pronto.

Also when someone chooses to type using single letters, poor spelling and punctuation it tells us a lot about his/her personality

10. ### WBahn Moderator

Mar 31, 2012
17,761
4,800
In other words, "Yo Dude, I want to copy your homework. Give it to me now!"

11. ### takao21203 Distinguished Member

Apr 28, 2012
3,577
463
schematics with many wires

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