Dark sensitive switch - Mod 12V supply to 5V

[adrianbodor]

Hy to all, I have a question, can this circuit be modified to use a 5VDC power supply instead of 12V

Here is the link,
https://www.electronics-lab.com/projects/motor_light/015/index.html

Thank you,

 

[Reloadron]

Your link didn't work for me but I found the attached circuit muddling through the site. If this is the circuit it could be modified to work on 5 Volts but the first thing that is a problem is a 12 volt relay coil that likely will not work at all on 5 volts. You would need to sub a 5 volt coil relay and make sure that the transistor could drive it. Then change some resistor values maybe. The values of R3 & R4 would be reduced so the LEDs work.

Ron

 

[adrianbodor]

Now the link works. I know the resistors for these 2 leds must be changed also the relay with a 5v coil but i don't know if the transistor can drive the relay.

The caps can be left to the values as it is?

 

[Reloadron]

The caps would be fine. You may need to play with R1 a little. R1 plus the pot plus the value (light & dark resistance) of the LDR determine when the transistor is turned on (saturated) to drive the relay. As long as you go with a relay coil that draws the same or less current than what is there it should work just fine.

Ron