Questions tagged [ldr]
A light dependent resistor (LDR) is a resistor where the resistance decreases with increasing light intensity.
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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, ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
user106458
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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 ...
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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 ...
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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 ...
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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 ...
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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-...
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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
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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/
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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How do I calculate resistance when I have the voltage drop?
This is my circuit:
3 volts in with a 1k ohm resistor in series with the LDR.
I have the voltage drop across the LDR but I need to find the resistance.
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Night light circuit wih switching bulbs
How can I connect a night light circuit such that one bulb is lit up on a sunny day and one is only lit up at night so that the two lights don't light up simultaneously? Also, can I use a SPDT switch ...
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How to adjust duty cycle of an existing square-wave, based on light level
I am making a wall-powered, battery-backed, BCD alarm clock with discrete logic.
I'd like to adjust the brightness of the LEDs based on light level, as this clock will be used on a nightstand. So ...
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MOSFET Fails After Few Uses
I am attempting to use a N-Channel Logic Level MOSFET as a switch for a phone charger that runs on a 42V battery.
I have a resistor circuit with an LDR that currently outputs 3.3v when LIT with a ...
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Best circuit to turn on a (5v heating pad) switch during the day?
Most of the circuit examples I'm finding online for LDR or other light-detecting circuits appear to be for turning things on at night. I'm trying to rig up a small heating pad under a birdbath using a ...
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How to build fast visible light detector
I need a circuit which can detect flickering of light too fast. I have Digital LDR Module which is too slow can I replace LDR with L14G2.
Digital LDR Module -
Digital LDR Circuit -
Can we ...
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