"The Medway Handyman" wrote in message
. uk...
Hi All

Had a job today, lady recently moved in, hall light had packed up.

Turned out to be a faulty dawn to dusk sensor. White plastic thingy about
80mm long, 30mm dia with a male bayonet one & a female the other.
Removed it, Robert is your fathers brother. Got me thinking though!

How do these things work? I can see the logic of 'it's dark, switch on'
but how do they stay on?

I assume they have a photo cell of some kind? Why doesn't the light
coming from the bulb trigger the sensor and turn the bulb off? Daylight
would trigger it and the bulb is much closer & brighter.


I'm confused.


--
Dave
The Medway Handyman

I suspect its down to frequencies of light; natural light must produce a
certain frequency of light the bulb does not produce, and when the sensor
detects it, it turns the light off cus it knows it must be day time.

Steve