I need help with a school project we're doing. The output is to have a timer that counts down starting from 1:59 to 0:switches and then stop until the circuit is reset.
-The minute hand is shown by an LED (lit = 1 minutes , not lit = 0 minutes) and the seconds are shown in a 7-segment display
-The 0:switches part means that a set of switches will indicate where the timer will stop ex. 0:15 - 0001 0101 , 0:30 - 0011 0000
I'm currently using a 74191, a 7447 for the seven segment display, and a 2Hz 5V astable multivibrator for the clock pulse.
Question: How do I make the timer stop using switches? Is there anyway for the switches to be considered invalid ( 00 ) if it is higher than 5 / 9? A schematic would be appreciated.
Additional Note: We're only allowed to use basic ICs like the basic gates, flip flops, synchronous up down counters, decoders etc.
-The minute hand is shown by an LED (lit = 1 minutes , not lit = 0 minutes) and the seconds are shown in a 7-segment display
-The 0:switches part means that a set of switches will indicate where the timer will stop ex. 0:15 - 0001 0101 , 0:30 - 0011 0000
I'm currently using a 74191, a 7447 for the seven segment display, and a 2Hz 5V astable multivibrator for the clock pulse.
Question: How do I make the timer stop using switches? Is there anyway for the switches to be considered invalid ( 00 ) if it is higher than 5 / 9? A schematic would be appreciated.
Additional Note: We're only allowed to use basic ICs like the basic gates, flip flops, synchronous up down counters, decoders etc.