Dark Detector

[tytower]

I got a circuit from hero999's site but I cant get an answer there so I want a circuit that runs on 12 volts DC for a solar garden light project run on battery and solar panel.
To conserve power I would prefer to switch the light on with a transistor or darlington setup. I need it to be adjustable to come on when dark.
Here is the circuit I am starting with . Can anyone assist with a revamp with useable resistor , trany and LDR values please?

 

[bipin411]

hi

I got a circuit from hero999's site but I cant get an answer there so I want a circuit that runs on 12 volts DC for a solar garden light project run on battery and solar panel.
To conserve power I would prefer to switch the light on with a transistor or darlington setup. I need it to be adjustable to come on when dark.
Here is the circuit I am starting with . Can anyone assist with a revamp with useable resistor , trany and LDR values please?

1.i think its becomes better to use photo transistor instead of drlingtonpair for switching.2.If u wanna -Ve cofficient type LDR there may be also applicable photo transistoe intesd of LDR 3. you can also change comparator configuration as ur avaliability, they are only alternatives.............. best of ur.....bye

 

[crutschow]

You could replace relay K1 with an N-channel MOSFET of appropriate current rating (source to battery minus, lamp between battery plus and the MOSFET drain). You would also need to reverse the input connections to the op amp comparator so that the output is high when the sensor is high impedance (dark).

 

[Space Varmint]

If you don't have a photo-detector handy and you have some 1n914 glass diodes lying around. They will react to light.

 

[MikeMl]

Read this recent thread. It is about a "dark detector"

 

[gary350]

This is pretty simple. A photo cell holds a relay ON all day long. When the sun goes down the relay open. This makes the other set of relay contacts. You can use either set of contacts to turn things ON or OFF.

If the tiny micro size relay can not handle the current it can be used to turn on a larger relay.

Did you know you can buy these already built for $15. They are rated 1000 watts.