Monitoring the fuses from the microcontroller with backup power is a good idea for our design.
AC Fuse Monitoring
This is a simple AC Fuse monitoring circuit, which will give Low (0V) to the microcontroller when the Fuse is okay and give High (5V) if the fuse is faulty. 4N26, an industry-standard single-channel phototransistor coupler senses the AC voltage and provides good isolation between the main AC input voltage and microcontroller input. The optocoupler consists of a gallium arsenide infrared LED and a silicon NPN phototransistor. The diode 1N4007 with 12V Zener at the optocoupler input prevents false triggering due to abnormal voltage drop on the main input. Another diode with a 120k resistor limits the return current on the neutral line.
This is a simple AC Fuse monitoring circuit, which will give Low (0V) to the microcontroller when the Fuse is okay and give High (5V) if the fuse is faulty. 4N26, an industry-standard single-channel phototransistor coupler senses the AC voltage and provides good isolation between the main AC input voltage and microcontroller input. The optocoupler consists of a gallium arsenide infrared LED and a silicon NPN phototransistor. The diode 1N4007 with 12V Zener at the optocoupler input prevents false triggering due to abnormal voltage drop on the main input. Another diode with a 120k resistor limits the return current on the neutral line.
This DC Fuse monitoring circuit is designed to supply the microcontroller with a 5V signal when the monitoring fuse is intact and a 0V signal when the fuse is faulty.
Under normal conditions, the DC current flows through the fuse, and the forward current of the Optocoupler's LED is below the threshold level, causing the Optocoupler to remain in the OFF state.
Once the fuse is faulty or blown, the optocoupler is switched ON, pulling down the logic output to the controller.
