Many amateur radio designs use fuses or self-resetting fuses as fuses. In order to quickly and easily detect the failure of your fuse (protection tripping) you can use the fuse blown indication circuit, which is described in our article.
A circuit where the indicator is an LED with three legs:
The considered circuit of the overload indicator Figure №,1 is suitable for those amateur radio constructions in which a fuse is provided (it is possible to use with any other fuse or element, for example, self-repairing fuse).
VD1, VD4 – 1N1705
VD2, VD3 – Д220А (its equivalent)
HL1 – ALS331A (or L239EGW or two separate LEDs of different luminescence color)
R1- Trimmer resistor 1 Kohm
FU1- Fuse
Description of the operation of the fuse burnout indicator circuit:
The presented circuit provides visual control of protection operation. For this purpose a two-color LED of ALS331A type with common cathode and three outputs is used. When the fuse FU1 is whole, HL1 glows green, and when the fuse blows, it glows red. This effect is ensured by using additional diodes VD1- VD4. Adjustment resistor R1 is necessary to set the threshold of HL1 LED glow.
