The circuit is a very simple comparator. It compares the voltage seen at pin 4 (set by D1 and R1) to the voltage at pin 5 (set by R2).
To run the circuit from 24V all you need to do is either use an op-amp with a 24V spply voltage, or regulate the voltage down to 12V for the circuit. Then swap out the zener with a 24V unit. R3 will need to be recalcuated based on the current draw of your LED. And you'd need a 24V buzzer.
Low Voltage Alarm
Posted - Jun 23 2011 : 10:49:33 AM
