Ambient light detector and lamp controller

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I am trying to devise a light (lamp) controller that will respond to
changes in ambient light levels. The idea is to operate a lamp in
reverse to the ambient level. In other words, as daylight falls, an
incandescent lamp would produce more and more light. I'm thinking a
couple of photocells, in some kind of bridge network or comparator
circuit, coupled to a readily available light dimmer switch.

 

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I am trying to devise a light (lamp) controller that will respond to
changes in ambient light levels. The idea is to operate a lamp in
reverse to the ambient level. In other words, as daylight falls, an
incandescent lamp would produce more and more light. I'm thinking a
couple of photocells, in some kind of bridge network or comparator
circuit, coupled to a readily available light dimmer switch.

You might be able to add a resistor style photocell directly to a
lamp dimmer if the dimmer is located where it can "see" the ambient
light. Just a small window on the dimmer and connect it to one leg of
the pot that adjusts the light - then you'd probably have to fool with
it because photo resistors are slow responding and the thing may
oscillate.

Plan B comparator looking at room light and comparing bridge voltage
to a reference voltage - only one photocell. The comparator tries to
raise the light level to keep the bridge balanced against the fixed
reference.

Then you have to deal with power line isolation too. Your circuit
would run on low voltage and need to interface with a dimmer working
at mains voltage? An opto-isolator.

It would be relatively simple to build it into a lamp dimmer so there
may already be something on the market.