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An outdoor PIR switch that popped a fuse, and when a new one was put in it glowed orange inside before blowing the new fuse.
This unit is an excellent example of design by someone with no real experience of PCB design involving 120/240V. The one routed anti-tracking slot is almost a token gesture inclusion to distract from all the other places tracks with high voltage difference between them pass close together. Tracking is when moisture or other contaminants cause a carbon track to gradually form across a surface between tracks and pads. Once it reaches a significant level it can start conducting current and flash over.
It's also an excellent demonstration of why prominent branded units often include a thermal fuse in the vicinity of relay contacts to kill the unit if any significant contact arcing occurs.
This is especially important with small relays with low contact gaps. Some loads, especially inductive ones, can cause sustained arcing between open contacts.
In the wrong circumstances, this unit could have caused a fire. Especially if protected by a high value fuse.
The dropper capacitors in these units tend to degrade over time and reduce in value. This one was a 560nF capacitor that had dropped to 400nF. It was probably still enough to do the job, but would have reduced the current available to the circuitry, possibly affecting the relay's operation.
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