Ceiling fan in lounge, wired to lighting circuit.
When switched off at night, the outside security light comes on.
Whys that then?
- posted
9 years ago
Elecktrickery 3
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- posted
9 years ago
Security light is wired on same local power circuit as the fan, and the light's inbuilt PIR board is susceptible to the voltage fluctuations caused as the fan spins down.
Try a different security light?
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- posted
9 years ago
Aha!
Not a problem, just wondered.
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- posted
9 years ago
The fan motor works by electricity producing a magnetic field which causes the motor to rotate. When the supply to the ceiling light is cut the motor acts as a generator for a very short time and as the magnetic field collapses it produces a high voltage pulse of electricity. This spike is enough to affect the PIR circuitry and cause it to switch on. Both fan and PIR should incorporate protective circuits to minimise this effect but often they are rudimentary or non-existent.
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- posted
9 years ago
In my previous house I had a feature where if I turned on a CRT monitor in my office, the lounge light came on! (it was on a touch dimmer with remote control)