Fuse Failure Indicator

This circuit indicates when a device is functioning or when its fuse has blown. It is a development of the Mains/Fuse Failure Indicator published in Elektor Electronics July/August 1995. It is smaller and cheaper than the previous design, even though it works on any mains supply voltage. A single bi-colour LED (D2) with separate anode connections indicates operating (green) or fuse failure (red). Resistor R1 limits the current through the LED to around 2 mA: the LED is thus reasonably bright. If higher brightness is desired, the resistor value can be reduced.