hi,
As you now want to display minutes and seconds, parts of the circuit diagram need to be redesigned.
I will post a modified circuit diagram early next week week.
EDIT:
Modified the design, the counter now counts in minutes and seconds. Click the link on this post.
The changes are mainly on the 74LS08 connections.
Check the drawing carefully, I have built the counter section, it works OK.
After 2 minutes the buzzer sounds for 5 seconds then OFF, the counter then restarts from zero for the next 2 minute count.
**broken link removed**