I am an extreme begginer when it comes to electronics-I am trying to build a darkness-detecting LED system for outside. Now instead of doing the logical thing like buying an outdoor light-I ripped open a cheap night light for an LDR and a mini torch with a rechargable battery/solar panel power supply and a switch.

As shown in the photos below, I planned to simply bridge the switch with the LDR and Bingo! But then I realised thats why they call it 'light dependant'. I have no clue how to invert the LDR-some help?

Thanks!

 

What voltage is the battery when it is fully charged?
Can you connect a multimeter set to read current, across the switch contacts when the battery is fully charged and tell us the current, please.

 

What voltage is the battery when it is fully charged?
Can you connect a multimeter set to read current, across the switch contacts when the battery is fully charged and tell us the current, please.

I believe the voltage is 3.6 V at full charge-I can not provide the current as I do not have a multimeter sorry.

 

Do you want the LEDs to snap on and off (more complicated) or would it be OK if they faded on and off as the light changes (simpler)?

 

I have no preference-fade is fine with me-thanks

 

This circuit will do the job. Left and right hand refer to your photo above. The value of R2 will need to be selected to set the brightness level at which it operates.

 

This circuit will do the job. Left and right hand refer to your photo above. The value of R2 will need to be selected to set the brightness level at which it operates.
View attachment 135653

Oh awesome! Thanks for making that-could you confirm with me the circuit symbols/components as I am unsure I am completley correct.

 

R1 - the LDR
R2 - a resistor to set the switch point, 1MΩ would be a reasonable starting point
Q1 - P-channel MOSFET LP0701N3 (TO92 package)

 

Ok awesome thanks so much-ill let you know how it goes once I source the parts.