This simple project monitors fuses on low voltage equipment, eg. power supplies etc.
The project makes an LED light up if a fuse blows, this gives a quick indication if the fuse has blown and the LED can be sited on the front or rear panel saving time when fault finding.
The fuse monitor can be made using one of two methods, the first method uses just four components, whereas the second method uses an IC and two components for each fuse that is being monitored. Both methods will be described in this article.
TRANSISTOR FUSE MONITOR
This simple circuit can be used to monitor one fuse in a circuit and light an LED if the fuse blows, the circuit diagram is shown below;
IC FUSE MONITOR
This fuse monitor utilises a 4049 inverter IC, this circuit also lights an LED of the fuse fails, this circuit can be used as a building block to add dual fuse indication (one LED for a pair of fuses) or can be adjusted to trigger a relay etc, (these adaptations will be posted at a later date)
The diagram is shown below:
The 1k resistor is used to 'pull down' the input if the fuse blows, this is to ensure the input is not left floating
