In the kit Blown Fuse Indicator Fuse is a common device that is used in every electrical or electronics equipments or devices. Fuse is a protective element of every device which protects the electrical equipments against high voltage.
In the kit Blown Fuse Indicator generally, when equipment indicates no power, the cause may be just a blown fuse. Here is a circuit that shows the condition of fuse through LEDs. This compact circuit is very useful and reliable. It uses very few components. Under normal conditions (when fuse is alright), green LED glow. Whereas the red LED remains off. When the fuse blows off, the supply to green LED gets blocked, and because only one LED is in the circuit, the red LED glows. In case of power failure, both LEDs remain ‘off’. This circuit can be easily modified to produce a siren in fuse-blown condition. An opto-coupler (MCT2E) is used to trigger the siren. When the fuse blows, red LED glows. Simultaneously it switches ‘on’ the siren. Two LEDs of red and green color can be used. Similarly two diodes are used to increase the voltage drop, since the two LEDs may produce different voltage drops.