Telephone Ring Detector

Analog Telephone Ring Detector

When this circuit detects the telephone ringing signal across tip and ring (60 to 105-volt RMS 20-Hertz sine wave), it will trigger the Optocoupler's phototransistor output and provide Low (0V) signal to microcontroller. Otherwise, it will give High (5V) to microcontroller.

12V Zener is added to prevent fault triggering from unwanted signals. 0.1uF, 250V capacitor is used for DC blocking and 10k 0.5W resistor is to limit the current passing through the optosiolator.

This circuit can drive relay or can be directly interface with any other outputs such as LEDs.

Fuse Monitoring Circuits

AC Fuse Monitoring   



This is a simple AC Fuse monitoring circuit, which will give Low (0V) to microcontroller when the Fuse is Okay and give High (5V) if the fuse is faulty.

DC Fuse Monitoring   

This DC Fuse monitoring circuit will give High (5V) to microcontroller when the monitoring fuse is Okay and gives Low (0V) when is fuse is faulty.