This is a Blown Fuse indicator circuit by LED Display. A Fuse be the equipment protects that use often most. Because of cheapness can use protect electronics expensive circuit. Generally when fuse torn us can know immediately. but in sometimes Fuse torn already we don’t know. such as in electricity automobile system brake system , the system delays the electric current very much, etc. Fuse torn get into trouble at we must know for immediately the safety.
Figure 1 The Blown Fuse indicator LED Display circuit.
So I would suggest this circuit is simple. It can show with LED that immediately when Fuse blown. See the illustration as Figure 1
In normally or Fuse is good, Current flow through it to D1-diode 1N4148 as forward bias, so cause Q1-PNP transistor do not conduct current, It not work so LED go out.
But Fuse blown or Damaged by high currents from overload, cause open circuit. So there the base current to Q1 it so bias or has higher current flow through R1-resistors, collector, emitter of Q1 and LED1 glow immediately.
by equipment value that show that note for Voltage Source 12V , but if friends want to apply to the level Volt the other.
As a result change value R1 and R2 get by can calculate from R1 = (Vin – 2) x 50 and R2 = (Vin – 2) x 10000/2. Think the work of the circuit has a little, It may help to give friends comfortably up.
How to builds.
This project is not used many components so can assemble on the universal PCB board.as Figure 2 and Figure 3 The wiring and placing components must be carefully for is the polarity of Diodes, LED , transistor BC558 correctly.
And see below…
I check Fuse OK, then put it in circuit next power supply to circuit, and lastly Short circuit! Ohh LED display immediately. This circuit works!
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