HELP! Countdown Timer with buzzer using 74xx IC

[Art_bits]

Hi guys! Can any one help me how to make a countdown clock timer (MM:SS) .. We have a project that has to create a countdown timer with buzzer, but I don't have enough knowledge about doing such things that's why I'm seeking for your help...
The timer can be set for xx min. For example 90 mins and press start. It has to count down from 90 to 0 and trigger an alarm after 90 mins for 1 minute.
I thinking of using 4 seven-segment (2 for Minutes and 2 for Seconds), and a button to set the time, Stop, Reset Buttons,
an LED will turn on when the count reaches 0:00

Using any 74xx family chips IC and other IC.. I need schematic for this!...
Thanks in advanced!

 

[djsfantasi]

Is this a school project? It may belong in a different forum.

I'd start by selecting the counter. It must have a load function and the ability to count down. Then, you'll need a way to detect and reset/carry the count. Take a look at a 74192.

Try getting one digit to work. Set a digit, count down to zero, stop counting and trigger a buzzer.

Or make a circuit that triggers the buzzer for one minute. My point is to break the project into smaller projects. Then the project won't seem as daunting.

 

[AnalogKid]

This is not a simple beginner's project. In particular, what method are you going to use to preset the counters? The basic counter circuit is not difficult, but the user interface could double the parts count.

ak