Dark/Light sensor using transistor
Automatic dark detector senses darkness. As the light level decreases and LDR meets the maximum threshold resistance, the circuit automatically switches on the LED D1.
Fig. Automatic dark sensor using transistor
Fig.Automatic dark sensor with variable resistor
A dark detector can be made using a variable resistor. The sensitivity of the circuit can be adjusted with a variable resistor.
High resistance-> more darkness to switch on the LED.
Low resistance-> less darkness to switch on the LED.
Automatic Light detector using variable resistor
A light detector senses light. As the light level increases and LDR meets the lowest threshold resistance, the circuit automatically turns on the LED D1. We can adjust the sensitivity using the preset VR1-10K.
LESS RESISTANCE(VR1)-> LESS DARKNESS TO SWITCH OFF THE LED
HIGH RESISTANCE(VR1)-> MORE DARKNESS TO SWITCH OFF THE LED
Fig.Automatic light sensor with variable resistor
Just swap the resistor and LDR to convert a dark sensor to a light sensor
Fig. Swapping resistor and LDR converts a dark sensor to light sensor and vice versa.
Category: LDR Engineering
Thanks, after a long search…this is the most complete DIY exist. I could successfully done both L/D sensor..
Sir…can i make a color sensor composed of red, green, blue, yellow, and orange.
Can i use these LDR’s to make a color sensor like these?
And can u help me make a schematic diagram on these.
Thankz You…
MY Group make this project…..<3<3
i want to make a sensor siren using LDR .can u sent me a diagram please.
can you show me a digrame of how i can make a automatic dark detector 12v dc using a led tail light thank you and god bless
thnx i will try it inshaallah gr8
i want to make a lamp for my aquarium with dark sensor. i want to use 6 white leds 5mm..can u pls post a diagram for me to follow. thanks
thnx i will try it inshaallah
hi there – great little circuit and easy instructions, thanks!
i wanna circuit to glow 100w bulb in dark senser with the help of DC voltage.
Well, you can do that using a relay. It is quite simple. see this example: http://www.ldrengineering.org/how-to-use-a-relay/
This page gives you the idea for using a relay and using 100W(AC bulb) operating with a DC based dark sensor. Be careful while using 220V AC.
I want to make a dark sensor that turns on 1 led when it is dark, another when the light is ambient, and one final led when it is bright. I havent been able to find any circuit based on this description on the internet and I wanted to know if I could get some pointers.
If it isnt possible, im okay with that! I just want to know if it is possible in one setup or if I need to make 3 sensors operate 3 individual LEDs, and if I can; could I be led to a link of the circuit? Im aming for something small and something I can enjoy making for myself.
Thank you very much for your quick response.
I will soon try the circuit.
If I use a 12 volt battery, what components need to be changed?
Thanks & Regards,
amdani
Today, I want to make automatic switch, to turn on my car head lamp based on this dark sensor. Is this your scheme can be recommended for that?
Actually, I’ve done this experiment from your scheme. With a relay (instead of LED), I hope my plan worked.
Apparently, I have problems; at the time of the light intensity changes gradually (in the afternoon), or at the time of the transistor base current for the process began to get saturation, relay shaking, of course, my bulb flashes great, even broken.
Do you have any suggestions to solve this problem?
Thanks & Regards,
amdani
Yes, i do have solution for this problem, if you make 741 based dark sensor, the relay does not shake or flicker/flutter. You can get the circuit here: http://www.ldrengineering.org/dark-sensor-using-741/
Please wait till 29.1.2011 so that I can make it an show you on video. Please ask if you have other questions.
this website has helped me a lot with my course work.