Simple Light and Dark Detector
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- เผยแพร่เมื่อ 24 มี.ค. 2013
- A very simple light and dark detector that demonstrates the concepts of voltage dividers. A video showing how the voltage divider resistor values were calculated will follow. Please reply using a complete sentence and a question mark if your asking a question. The resistance in the first case is 330 ohms and for the second case the resistance is 2.7K. This is dependent on the particular photocell you use.
Another excellent, simple but detailed explanation. Thanks.
+Elecnut Thank you for watching and providing this inspiring comment.
you smart man because you can explain to us and without transistor and complication
Shit works! Most simple dark-sensor circuit I've seen. Well done
Thanks! Hope you had fun with it.
Its nyc Idea and project ... However i need help please share me the componenet value which can i use and i want to use relay for switch on while in light ..please suggest me which relay can use for this
Great job
I have one more question,that is,Will the LDR's sensitivity get damaged with usage?or will it be fine for long time?
No, the LDR should be ok as long as it does not get hot during operation.
How many volts did you use to power up the circuit? Thanks! More power!
I used a 9 volt battery.
what is the resistor using in the second circuit
+CHANDANA CHOUDHARY The resistor in the second circuit is doing two things: limiting the current through the LED and programming the the voltage divider to light the LED when the appropriate conditions are met.
Hi, please help. I tried your project and no matter what I've tried, I get the exact opposite results, the LED goes off when its dark. What am I doing wrong? I'm trying to teach an after hour school club and would like them to create an automatic night light.
The following is a link to the schematic for an LED-ON when dark. You may need to adjust the resistor value for your particular photocell. www.circuitlab.com/circuit/295y86/led-voltage-divider-light-off/
Thank you, for answering, and so quickly as well. It works a bit better now. Like you said, I have to find the correct value for r2. If I may bother you again, how do I adjust the value for r2, if I'm not sure what value the LDR is?
Photocells come in all different resistance ranges but once you adjust it for your particular photocell it should work for that type.
During normal lighting conditions if the LED is ON increase R2 until it just turns off. Turning off the lights should turn the LED on since the photocell resistance and voltage across the photocell increase.
Different color LEDs will also change the behavior since Red LED's require less voltage to turn on then Green LEDs.
A transistor version works better but I like to keep it simple - at first - as an exercise for my students. I make them calculate the proper resistor values for both circuits based on the photocell resistance and the LED forward voltage.
Have fun.
The following link is a video I produced for the procedure for making an LED-On-with-light photocell circuit
th-cam.com/video/JWKVgTOgm0Y/w-d-xo.html
wtf!!!! it's working thank you man it's perfect
Bilader bende olmuyor ya yardım etsene
Risister value
Is it the same resistor you use in example 1 and 2?
No. At 0:34 the text mentions the resistance is 330 ohm and at 2:09 the text mentions the resistance is 2.7K.
How about adding both LED and Buzzer along with a transistor?
You can drive both with a transistor.
How can we adjust its sensitivity with light??
Variable resistance?????
A transistor version will be more sensitive.
how much voltage you have given?
9 Volts
Why adding a transistor makes it even more sensitive?
We are using the non-linear properties of LEDs to make this work and under certain conditions the LEDs are being driven with very small currents to make them light. A transistor can increase the sensitivity by being able to react to much smaller changes in voltage and resistance, drive the LEDs with higher currents and create a better snap-on effect.
I originally created this project to help my students understand how voltage dividers work. Using LEDs in the lab makes it a little more interesting and challenging.
Could you show it from a different angle?
The video is 4 years old so that would be difficult. What are you specifically looking for? Maybe I can explain the situation.
Dorian McIntire well, I tried this circuit on my breadboard with an N2222 transistor and it didn't seem to work. I can't really set up circuits from schematics so I was trying to make sure I put everything in the right place. Could it just be my transistor?
This circuit does not use a transistor. It just uses a photocell , resistor and LED. Another video can be found at the following link: th-cam.com/video/JWKVgTOgm0Y/w-d-xo.html
send me circuit diagram and numbers of components
👍
Thanks.
photo cell ohm