Let's try this again.
I have an outdoor floodlight fixture with a photo-cell to turn it on
at dusk and off at dawn. It is not compatible with CFLs. If I cover
the eye so it thinks it's always dark and therefore will always be on,
will a CFL work, or is the circuitry different such that the CFL will
have a shorter life, even though it will always be on?
Part II: If, for the previous question, it will work, I will add a
screw-in photo-cell that works with CFLs for only $8. Then, it will
be on only at night and will be cheaper than buying a new fixture.
The usual photocell lights may not turn on fully at twilight
conditions, and the CFL's don't like that. If the photocell operates
a relay, so the light is fully off or fully on, then the CFL will work
It's very unlikely that the photocell operates a relay since they are
pretty much never used in those things. Mechanical failure rate is
too high. It probably has a triac that is not compatible with cfls.
I bought 3 lamps from the Borg without even knowing they have photocells
in them. I could turn that feature of but I left it set to light dusk
to dawn and all three CFL's have been working for months now. If the
cheap photocells in the lamps go bad, I'll bypass the photocells, wire
them direct, and put them all on one heavy duty photocell. And if that
doesn't work, I'll make the photocell turn on a relay which will give
power to all three lamps, I know that WILL work.
The "photocells" in light-sensitive switches or fixtures or whatever
you want to call them are normally variable resistors whose resistance
changes with the light that falls on the sensor. This in turn is used
to control a semiconductor called a "triac" which can control the
output, either directly, or by operating a relay. The relay, because
of its mechanical nature, is either on or off. But, if the triac
output is connected directly to the output/lamp socket, in
transitional lighting levels, the triac will only be partially
conducting, just like a light dimmer, and that is what the CFL's don't
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