Tired of replacing fuses everytime they blow? Use an electronic fuse.
It will still "blow " and protect your gadgets, but you don't need to buy a replacement fuse. This "fuse" can be "rehabilitated" by just resetting it.
This circuit is the electronic equivalent of a circuit breaker. Though, you might say a circuit breaker is cheaper and easier to install, constructing this
one will enhance your understanding of the sensor technique.
This electronic fuse uses an N-channel power FET as the high current sensor. The FET functions at the same time as the actual circuit breaker that cuts-off the
ground line of the load, once the current exceeds the maximum allowed value.
The cut-off current can be adjusted through the pot P1 from 0 to 5A. Remember, the circuit can only handle a maximum current load of 5 amperes.
Do not overload this circuit if you do not want to fry it. The power FET becomes hot in time, so it must be heatsinked.
Use also the proper wire gauges in wiring the circuit to its inputs and outputs. Using the wrong wire gauge will damage the circuit.
A relatively extensive test is needed before you release this "fuse" for a real long time protection job.
You must connect either C1 or C2 to the base of transistor T2. C1 will cause the fuse to blow "softly" while C2 will cause it to blow instantly.
Use different resistor values (high wattage!) in series with an ampere meter to simulate different current loads. Adjust the pot P1 until the fuse "blows".
Resetting the fuse is simple: Just disconnect its power supply, and the circuit is reset and ready to protect your gadgets again.
Parts Placement Layout
External Wiring Layout
Electronic Circuits volume 1.0 - Circuit Nr. 24
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.