Simple electronic fuse. This is perhaps one of the simplest
electronic fuse circuit one can make. The circuit uses only one
transistor, one SCR, one push button switch and two resistors.
The working of the circuit is very simple. Initially the load
current flows through SCR and resistor R1.The value of R1 is so
selected that, the maximum load current multiplied by the
resistance of R1 is equal to 0.7 volts. When the load current
exceeds the maximum value the voltage drop across R1 becomes
more than 0.7V and switches transistor Q1 ON. Now the transistor
completely bye passes the load current and the current through
triac falls below the holding current. This makes the triac OFF.
When SCR is OFF there will not be any current flow through R1
and so the voltage across it falls to 0.This makes the
transistor OFF, completely isolating the load circuit.The fuse
can be resetted by pressing S1.When S1 is pressed the SCR is
again triggered and remains latched to conduct the load current.
- The circuit can be assembled