With Instructables you can share what you make with the world, and tap into an ever-growing community of creative experts.
World's best Dark / Light Sensor! NO Integrated Chips!! No NPN, PNP transistors !! Only an LDR and a Resistor !!
1.Just connect any leg of LDR to any leg of LED. You can increase the light sensitivity by connecting two or more LDRs "in parallel" (like i have). 2...
1. Simple sensor circuit - actually no circuit at all! 2. No soldering required - relief for those allergic to it ! (like me!) 3. I have just pressed ...
Here is a simple schematic circuit diagram of the dark detecting sensor circuit for led...
We have a be nice comment policy. Please be positive and constructive.
We noticed you attached photosto your comment.
Hi please help me with this? - im a total newbie trying to learn how to dabble in the "dark arts" :-) Cant get my circuit to work and dont know whats wrong. Here are the various parts i have used.
Bc547; Tip127; 2n3904 - could this be the problem? The tip127 is the only PNP Transistor i can see according to the data sheet...
3x Different types of Leds. Red:1.2vF White :3.2vF,
3x differnet types of light detectors
- Photo Transistor 940nm
-Photo Sensor 940nm
Battery i am using is a 1.0ah 4.1v battery (4.1v is actual tested voltage)
2x POTS, 1x 1k, and another 10k pot.
Doing above on a breadboard
The problem is, The both LEDS stay on when connected, they just get brighter with more light, it seems my circuit is more of a light detector that switches LEDS on when it detects light rather than the opposite way around?
Ive tried switching the transistors, switching the leds, switching the POTS, and some other resistors i had (not sure of spec right now) but still cant get it right?
what other info can i add for you to assist?
Probably, interchanging the Emitter and Collector connections of your pnp should do it.
Search for "Dark Detector" (Solar) circuit, here or on google and compare your diagram....
hope it helps, since you have not provided a link to your circuit...
Hi Pandyaketan - Thank you so much for your response - i was going nuts trying to figure it out after over 10-12 hours of tampering, changing etc. Turns out it was the resistance value leading to the (Base) of the transisor - the resistance was not high enough, i used a 300k resistor from (+) to Base on one side, Photo-transistor on the other side of Base (transistor in the middle of the board -using breadboard).
See below image - i used a different schematic.
Again, Thank you for your assistance.
i dont get how the ldrs even effect the circuit the are beyond the ledplease help me understand
LDRs behave as light switch...
they decrease resistance, when light falls on them and complete the circuit....
so just wire two ldr's to each leg of a led? thats it? well and power source
and a resistor 10 KOhm (upto 150 kilo ohm), to the positive, as per circuit in the I'ble....
Trophy Hiding Placeby peytonlamoureux24
Dark Sensor ( light sensor / automatic street light )by Er Varun Goyal
LED AS A LIGHT SENSORby TAPAN MOJIDRA
How to make a Dark Sensorby eaglerobot
Motion Sensor: Teach Vestibularby anipotts
Light Sensing LEDsby Bot1398
Sensor without IC Chip!by pandyaketan
light sensorby Mahitchima
(w/ Video) Basic Arduino Robot, Light Seeker!by Chowmix12
Darkness Direction Sensor DIY Experiment easy by bastelking
Join 2 million + to receive instant inspiration in your inbox.
Download our apps!
© 2015 Autodesk, Inc.
By clicking "Create Account" you are indicating that you have read and agree to the Terms of service.
Already a member? Login »
Enter the email associated with your account and we will send you your username and a temporary password.
Not a member? Sign Up »
Want to go pro?
First step is to sign up.
By clicking "Sign me up!" you are indicating that you have read and agree to the Terms of service.