Fuse blowing is common problem, but is so tedious to go and check because every time it may not blown. Here is a simple circuit of fuse and power failure indictor,for indicate the power failure by giving alarm. The logic of this circuit is so simple and it also overcome the problem of checking every time.

Circuit Description of fuse and power failure indicator

The entire circuit of fuse and power failure indicator is build and fabricated around LDR, timer IC and LED. Here LED get power-supply from AC source which is stepped down by transformer X₁ and further rectified by diode and changed to regulated 6V D.C. with the help of regulator IC 7806 (IC₁). Here LED₁ and LDR₁ are kept in a cabinet together. Transistor T₁ and T₂ is used as cascade amplifier which amplify the divided voltage from LDR₁. Trigger is given to pin no 2 of IC₂ from the collector of T₂. Here timer IC (IC₂) configured as monostable multivibrator and its output is given to reset pin 4 of IC₃ which is configured as astable multivibrator. The high output is given for about 7 second from IC₂ to IC₃. IC₃ generate audio frequency and connected to loudspeaker. An alarm sound is produced from fuse and power failure indicator, indicating the power failure.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 100 Ω

R₂, R₄, R₆ = 10 KΩ

R₃, R₅ = 1.5 KΩ

R₇ R₈ = 1 KΩ

VR₁ = 10 KΩ

VR₂ = 100 KΩ

VR₃ = 1 KΩ

Capacitors

C₁ = 1000 µF/25V

C₂, C₄, C₆ = 0.01 µF

C₃ = 100 µF/16V

C₅ = 0.47 µF

C₇ = 33 µF/16V

C₈ = 0.47 µF

Semiconductors

IC₁ = 7806 (regulator IC)

IC­₂, IC₃ = NE555 (Timer IC)

D₁ = 1N4001

Miscellaneous

X₁ = 230V AC primary to 9V-0-9V, 250mA secondary transformer

LED₁ = White

F₁ = Fuse 500 mA

S₁ = ON/OFF Switch

S₂ = Push-to-on switch

Batt₁ = 6V Battery

LS₁ = 8Ω, 0.5W Speaker

LDR₁