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Questions tagged [ldr]

A light dependent resistor (LDR) is a resistor where the resistance decreases with increasing light intensity.

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Automatic on and off light strip [duplicate]

I am trying to make an led strip turn on and off automatically based on sunlight. So when it is dark the lights will be on full brightness and when it is daytime the lights would be off. The led strip ...
Fatema Ali's user avatar
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1 answer
66 views

How does this LDR circuit work? [closed]

All I know is that when I turn the lights off, the LED should light up, but I don't know how and why it works. Can you help me? I'd like to know how it works. The 10k there is a potentiometer. The ...
fireBreaker_2007's user avatar
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1 answer
43 views

Is there a way to use multiple Ldr inside a darkness sensor?

im trying to make a darkness sensor with mulpiple LDRs, the idea is that if all the LDRs are in the dark, a light in a led strip is turn on, otherwise, the led strip stays off. I have manage to make ...
rey kittan's user avatar
1 vote
1 answer
86 views

LED light bulb is flickering when switched on

I am a Physics Major student and have to do a project in our end sem. Since we read a lot of theory and workings and very less practicals, I am a bit weak in electronics. So here is the problem. Our ...
Mrinmoy Sarkar's user avatar
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0 answers
145 views

What analog component(s) can I replace a relay with

I'm extremely new to electronics and have a college group project to build a traffic light using only analog components (ICs are allowed), my subsection is to design and build the driver unit and a ...
OR13N 's user avatar
0 votes
1 answer
87 views

Long distance light detection in daylight [closed]

I am attempting to develop a system that is linked with streetlight lamps. There are challenges that I can think of: Light sensing in daylight (or climate changing) situations. Long distance (20-30m) ...
MiniJ's user avatar
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1 vote
1 answer
76 views

LED brightness control with limit and LDR

I made a digital circuit that follows the signal of an LDR, setting on a LED when the voltage is grater than the limit. It also changes the intensity of the brightness as the voltage rises and fall, ...
Lucas Czemko's user avatar
2 votes
1 answer
50 views

Sensor components to read device status indicators/LEDs on a separate device

I'm planning to build a circuit that reads LEDs displayed from another separate off-the-shelf proprietary system without reverse engineering or modification (which would cause warranty issues) of that ...
dazzleworth's user avatar
-2 votes
1 answer
215 views

BC547 & LDR with multiple LED's

I'm new to electronics and I want to make a LDR controlled night light with multiple led's. I use a 3V battery pack, which I can power the LED's with, without the LDR setup it works just fine. I have ...
pythorzz's user avatar
2 votes
3 answers
238 views

Tuning photoresistor circuit with resistors

I've done small circuits for a long time, although nothing more than a few basic ones. I am now trying to control an IO-signal to Raspberry Pi. Since Raspberry Pi doesn't have analog pins, I came ...
Ljuslykta's user avatar
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1 answer
86 views

Turn on LED for fix time when box is closed

I have a box which is used to put PCB in it when we are not using PCB. I want to turn on a UV blue LED for 1 minute when box is closed to cleanout the inside of box. I cant use limit switch as I don't ...
Zunuran Nasrullah's user avatar
2 votes
4 answers
197 views

Blue UV LED Timer Circuit

I have designed a PCB for mouth guard device and also its enclosure is ready in which PCB will be placed when its not in use. I want to use a UV blue light for UV sterilization inside the box. Now the ...
Zunuran Nasrullah's user avatar
0 votes
3 answers
117 views

Using an LDR and PNP transistor to automatically dim 12 V common anode 7-segment displays

I have designed and built a GPS time derived six digit digital clock using an Arduino. the digits are LED 2.3 inch common anode 12 V devices (because that's what I had!) and, after much work to drive ...
Mark Borchers's user avatar
0 votes
1 answer
255 views

Trouble with laser light alarm system

My alarm system circuit consists of: BC-547 transistor 2.2 kΩ resistor An LDR 3.7 V lithium-ion battery connected with a switch LED light Buzzer Laser light The resistor is attached to the collector ...
Shaurya's user avatar
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0 answers
60 views

Why does my power supply circuit not function correctly when connected to a load circuit?

My transformerless power supply on the left side of the voltmeter outputs 24V/12V until I connect it to my load circuit on the right. The voltage coming out becomes and stays at 1.5 V at most and I ...
batekoi's user avatar
0 votes
1 answer
177 views

How can I incorporate an LDR in a 555 flasher circuit? [closed]

I have designed this flasher circuit using a 555. I want to incorporate a light dependent resistor (LDR) to start flashing the LEDs only when it is dark. I can't figure out where I should put the LDR ...
Bhargav Rajyaguru's user avatar
1 vote
1 answer
120 views

Can I use a TRIAC as an AC switch and an LDR as a switch controller to turn on and off a LED bulb?

I want to use a TRIAC as a switch for an AC light bulb and turn on the bulb when it gets dark and turn it off when it gets light using an LDR. I want to fully cut off the bulb below a certain ...
Divakar Aryal's user avatar
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1 answer
70 views

Portable LED staircase light

I need to make a portable LED staircase light that uses a BPW34 photodiode. It should enable the LED driver when incoming light is below an adjustable threshold, and disable the LED driver when ...
fritz55's user avatar
  • 23
2 votes
1 answer
5k views

Low-voltage battery cut-off circuit for 3.7 V lithium

I am looking for something even simpler than this, with low power consumption (so no relay): https://youtu.be/8GQrTZb9T_c?t=158 I need a circuit which can be built from basic components which can cut ...
user avatar
4 votes
3 answers
821 views

How do I control the sensitivity range of an LDR-controlled LED?

I'm trying to make an LED dim according to the ambient light (darker ambient -> brighter LED), through use of an LDR. I'm using a voltage divider with an NPN transistor (BUL38D). I've tried ...
Guilherme Gaspar's user avatar
0 votes
1 answer
177 views

Automatic dark detector: base voltage

Here we have the typical “automatic dark detector” circuit: Let’s assume LDR=5Kohm with light, and LDR=2Mohm in darkness, the battery is 12V instead of 9V, and the transistor has a forward voltage ...
ElectroNewbie's user avatar
17 votes
8 answers
2k views

How can you turn perceived brightness (log scale) into a linear analog output using an LDR?

This question is not about how to make illuminance (in lux) a linear function of voltage! It's about linearly representing the human perception of brightness, which itself scales logarithmic to the ...
Niklas's user avatar
  • 298
3 votes
5 answers
3k views

What is the mathematical relationship between the resistance of an LDR and light intensity in lux?

I have been surfing the internet and my physics books for the relationship between the resistance of an LDR and light intensity (a formula), and so far I have found nothing. If any of you have a ...
Manessa's user avatar
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0 answers
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Problem with LDR + PIR

I am using a TEMT6000 LDR and a PIR to turn on outdoor lighting, well that's the plan. The LDR and PIR are in the same housing, and after some searching on forums, I found that I can combine the V-...
snewpers's user avatar
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0 answers
229 views

LiFi with Arduino

I am trying to learn LiFi by transferring data between two Arduino UNO boards with sample code as in link below. https://create.arduino.cc/projecthub/hamiran1997/li-fi-system-36ff5b?f=1#comments ...
Meiyappan Kannappa's user avatar
3 votes
1 answer
115 views

Automatic LDR switching circuit

I would like to create an energy efficient LDR evaluation circuit. The circuit should provide the possibility to connect an external LDR (R8) or use an internal, permanently installed LDR (R25). When ...
Kleeblatt Paul's user avatar
0 votes
1 answer
658 views

My light-dependent resistor gives a fluctuating serial output

I'm a high school student trying to make a light tracking single axis solar panel. I am using an Arduino Uno rev3 board. When I first finished building it, the system failed to operate. I spent a few ...
ElevenBits's user avatar
0 votes
2 answers
426 views

Need help on solar light auto on off dawn to dusk

I have 36 Ah battery. I will charge it through solar change controller or through inverter. I want to connect this battery to two 9 watt DC LED garden lights which will turn on and off automatically ...
Bikash Lakra's user avatar
0 votes
0 answers
537 views

ESP32 digital IO output inconsistent voltage

I have a problem which I have been fighting with for several days now. I can't see any possible solution. Maybe someone could give me push in the right direction, that would mean a lot. I ordered 5 ...
Kleeblatt Paul's user avatar
10 votes
4 answers
1k views

Night light broke after trying to dim LEDs

I purchased a cheap night light that plugs directly into a 240V wall outlet. It has three color changing LEDs. The problem was, those LEDs were way too bright. I decided to modify that night light a ...
polemon's user avatar
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0 votes
1 answer
125 views

Will this circuit work on a Raspberry Pi?

There a lot of articles on websites regarding the use of LDRs connected to a Raspberry Pi. As an example, using an ADC or using a built in library. I'm interested with my own design below and since I ...
chuackt's user avatar
  • 609
1 vote
3 answers
766 views

How to prevent relay damage due to switching that is not smooth

I am driving a 9V relay from the output of a comparator (LDR sensor) and the relay gets damaged due to rapidly changing voltage from the comparator when light on the LDR is small. The relay starts ...
p_karis's user avatar
  • 103
0 votes
1 answer
398 views

PWM regulated by a LDR , the darker it is outside, the darker are the LEDs

I'm doing a hobby project with an electronic panel. The panel is going to have some white LEDs under switches names. Since im going to use the panel at all times of the day I want the LEDs to be ...
Piotr Czerwonka's user avatar
0 votes
1 answer
108 views

What resistor should I put in series with an LDR for minimum current draw when using an Arduino Nano?

Is it possible to use 10k ohm resistors without having any noise issues? I plan on making a solar tracker with 4 LDRs in parallel so a low current draw is imperative - so is a low noise distortion.
A.H.Z's user avatar
  • 633
1 vote
2 answers
1k views

Is this LDR and TRIAC circuit advisable for real time application?

Would you suggest below circuit? Will it work for a long time? What are the advantage and disadvantages of this circuit? https://envirementalb.com/automatic-street-light-circuit/
Manu Devappa's user avatar
0 votes
2 answers
291 views

How would you connect a light dependent resistor / photoresistor/ CdS cell at a right angle to a surface mount board?

My project uses light dependent resistors (aka photoresistors or CdS cells). All the ones I can find for sale from the usual suppliers are through hole type. ie. they have two wire legs. The PCB I'm ...
Le Roux Bodenstein's user avatar
0 votes
3 answers
914 views

I'm making a simple dark sensor project with a light dependent resistor (LDR) and I want to replace the LED with a buzzer but it doesn't work

I replaced the resistors with small ones to give the buzzer more current,but itstill doesn't work. I checked my buzzer and it's working fine. The circuit works perfecly with the LED in the breadboard ...
Ahmed Lotfy's user avatar
0 votes
1 answer
83 views

My NE555 circuit triggers falsely when connected to the mains using a 5V adapter

I have designed a laser security system using an NE555 in monostable mode with a potentiometer to adjust the pulse length. Another NE555 (U2) ciruit is used for delaying power on the monostable ...
Hanzala19's user avatar
0 votes
1 answer
161 views

Trouble understanding a given circuit for an LDR pulse sensor

I'm a second year physics student, part of a group, and we're trying to build a pulse monitor following this guide. This is the schematic I'm having trouble to understand: I have basic knowledge of ...
Evicten's user avatar
0 votes
4 answers
283 views

Is it possible to solve for the values of this grid of photoresistors in software?

In this question a circuit was set up as shown: The idea is to power the rows one at a time, and read off the voltages of each column. But there's a subtle problem. There are alternate paths to ...
Mike's user avatar
  • 3
0 votes
2 answers
800 views

How to connect LDR to LED by using battery 5V

I connect LDR to LED by using battery 5V like this circuit. I adjust value of VR and LDR but it's not work. LED still 0.00V. How to fix circuit for make LED to 5V
user58519's user avatar
  • 111
0 votes
1 answer
146 views

LDR connect to opamp switch very fast when low battery

I use LDR connect to opamp like this circuit. I use input is 5V from 7805 connect to battery 12V. When relay turn on the light about 2 hour then relay switch on and off continue very fast. How to fix ...
user572575's user avatar
1 vote
1 answer
855 views

Where to put a buzzer so that it goes off when there is light (and should stop when there is dark)

I've successfully created (and breadboarded) this circuit: simulate this circuit – Schematic created using CircuitLab I cannot figure out where to put a buzzer so that it goes off when the LED ...
wajmo's user avatar
  • 23
1 vote
1 answer
325 views

What's wrong with my basic light/dark detection circuit

I've just started playing with electronics, and wanted to make a light/dark detection circuit without using a transistor (they are too advanced for me at this moment.) I decided to use these ...
wajmo's user avatar
  • 23
3 votes
4 answers
4k views

How fast is a photoresistor?

I am trying to build a skipping rope jumps counter. My preliminary design consists of an LDR, a laser diode, and sn Arduino. Basically, the LDR and the laser diode are placed exactly opposite to each ...
hegemon8's user avatar
  • 115
0 votes
0 answers
124 views

How to implement an equation in assembly language using PIC18F and display its result on LCD?

I had a project that requires to measure illuminance(lux) using LDR and display the result on LCD. Thanks to some references from Google, I had managed to build a equation that shows relation between ...
Thanh Nhon's user avatar
0 votes
1 answer
113 views

Solar tracking using an Arduino Uno

I'm trying to design a dual axis solar tracker using an Arduino Uno-R3. Basically it just takes the input from the LDR and outputs the PWM signal to the two 9g servo motors for each axis. The ...
Wkayy10's user avatar
0 votes
0 answers
147 views

How to select resistor value for LDR

I want to try making an 230 VAC bulb that automatically turns on/off using a relay a transistor an LDR I have collected the following components: a 9 V battery a 9 VDC relay an LDR a BC457 ...
sangpo Sangpo's user avatar
1 vote
2 answers
399 views

NE555 in a light detecting circuit

I'm completely new to electronics but my degree gives me a basic course with a project at the end. I built this small circuit to detect when a light is shined on the LDR to turn on an LED so ...
Tommy Normandin Racine's user avatar
1 vote
1 answer
2k views

Is there an equation for the relationship between illuminance and the resistance of a light dependent resistor?

All I've seen on this is: R = A.Ea. where E – illumination (lux), R – resistance (ohms) and A, a – constants. The value of ‘a’ depends on the CdS used and on the manufacturing process. Values usually ...
hannah's user avatar
  • 51