Simple Photoresistor Circuit

[gwpmike]

I want to create a simple circuit that is essentially the opposite of a dawn/dusk circuit.

A dawn/dusk circuit would allow a light to turn on (or close the circuit) when it is dark outside, and would turn the light off (open the circuit) when it is light outside. I want to do the opposite.

I want a LED to be able to turn on ONLY when it is light outside. I want the LED to not turn on when it is dark outside.

In other words, close the circuit when the photoresistor detects light, and open the circuit when the photoresistor does not detect light. Please see the attached diagram.

 

[alec_t]

In most dawn/dusk circuits there is a resistor and photo-sensor connected in series between the power rails. Essentially, all you have to do is swap the two over.

 

[audioguru]

You need a transistor emitter-follower in between the photo-resistor and the LED.

 

[dr pepper]

I found this light sniffer circuit using a few comps, and the 'sensor' is a led:

https://rustybolt.info/wordpress/?p=2521

Welcome here.