PAGE 133 OF 150 · POWER SUPPLIES & BATTERIES
Fuses and Circuit Protection
A fuse breaks the circuit when current gets too high.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Why fuse
A fuse protects wiring from overheating when a fault draws too much current. It is a deliberate weak link that breaks the circuit first.
- Choose a rating a little above the normal current: a 3 A strip suits a 5 A fuse.
- Put it on the positive wire as close as possible to the supply.
- Fast-blow fuses react quickly; slow-blow types tolerate brief surges.
Rules
Never replace a fuse with a larger one or a wire to stop it blowing. Find the fault instead. Resettable polymer fuses suit low-current electronics.
REMEMBER
A blown fuse is a warning, not a nuisance.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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