Blown Fuse Tester Using NPN Transistor BC547

Circuit Description:

1. NPN Transistor (BC547):
   • The NPN transistor is used as a switch. Its base is connected to a biasing resistor and the fuse to be tested.
2. Resistor (R1):
   • R1 is connected between the positive voltage rail and the base of the NPN transistor. It is used for biasing the transistor.
3. Indicator (LED or Buzzer):
   • The indicator is connected to the collector of the NPN transistor. When the transistor is biased, it controls the current flow through the indicator

How It Works:

1. The fuse to be tested is connected in series with the base of the NPN transistor.
2. When the fuse is intact (not blown), it allows current to flow through the base of the NPN transistor.
3. The biasing resistor (R1) limits the current flowing into the base of the NPN transistor.
4. The biased NPN transistor allows current to flow through the indicator (LED or buzzer), indicating that the fuse is intact.
5. If the fuse is blown, there is an open circuit, and no current flows through the base of the NPN transistor.
6. The NPN transistor remains off, and the indicator does not light up or produce sound, indicating a blown fuse.