ByPass Photoresistor? Any Electrical Engineers out there?

[rhodges]

What I'd like to do is, somehow, wire a relay, that, when energized can bypass the photoresistor and "force" the ir illuminator to turn on. If the relay is not energized, then the ir illuminator will turn on when the photoresistor turns it on.

Attached is a picture of the bottom of my CM ir illuminator. The 2 pins in the very center are for the sensor. I read up that in the dark (when I want it to turn on) the resistance is high and in the light it is low.

I think the relay would need to cut the sensor out of the circuit when I want to force it on. I'm guessing I couldn't just open the circuit, but would need to bypass the sensor and provide a resistance across it to simulate darkness?

Any electrical engineers out there that can chime in?

 

[AlpineWatch]

Old post I know, but if I were you, go ahead and 'open' the circuit to the photocell, I doubt the circuit has a window where the photocell value is only valid between two values. Also photocells tend to be VERY high resistance when dark.

Give it a try.

edit: That LM358 is a an opamp being used as a comparator. Again, it's likely only comparing the photocell 'value' from a set point. Above it - IR off, below it - IR on.

What I'd like to do is, somehow, wire a relay, that, when energized can bypass the photoresistor and "force" the ir illuminator to turn on. If the relay is not energized, then the ir illuminator will turn on when the photoresistor turns it on.

Attached is a picture of the bottom of my CM ir illuminator. The 2 pins in the very center are for the sensor. I read up that in the dark (when I want it to turn on) the resistance is high and in the light it is low.

I think the relay would need to cut the sensor out of the circuit when I want to force it on. I'm guessing I couldn't just open the circuit, but would need to bypass the sensor and provide a resistance across it to simulate darkness?

Any electrical engineers out there that can chime in?