Questions tagged [ldr]

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

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1answer
18 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 ...
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0answers
41 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: Schematic source page on CircuitLab I cannot figure out where to put a buzzer so that it goes off when the LED shuts down, and the buzzer to ...
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1answer
77 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 ...
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3answers
1k 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 ...
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0answers
36 views

Long tailed pair not working to compare signals from 2 LDRs

I've been trying to compare my signals from 2 LDRs to feed into Arduino's ADC. However I can not get any gain from my differential amplification. The problem comes when I have high resistance from 1 ...
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0answers
42 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 ...
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1answer
48 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 ...
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0answers
42 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 ...
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2answers
92 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 ...
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1answer
145 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 ...
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6answers
2k views

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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1answer
48 views

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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2answers
67 views

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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1answer
98 views

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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1answer
52 views

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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2answers
218 views

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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2answers
92 views

Dark circuit using LDR

Could anyone please help me to draw the wiring diagram for this connections? I have made this circuit but the problem is that I must attach the diagram of how all of these are connecting with each ...
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1answer
143 views

Need help in designing of circuitry. (Power Electronics)

The circuit is supposed to detect ambient light and react accordingly. When there is high illuminance the LED should be dim and when there is low illuminance the LED should be bright. The transistor ...
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3answers
125 views

How to add a LED indicator to report LDR sensor error using PIC?

I have this simple light sensor project using LDR. The PIC reads an analog signal 0-5V from LDR and will turn on the relay ON when it's bright on and off when it's dark. I want to add a simple LED ...
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2answers
106 views

Can someone explain this project to me? Can you explain the schematic so I understand how it works? [closed]

https://electronicsprojectshub.com/how-to-make-an-automatic-night-light-using-ldr/ Can someone explain this project to me? Can you explain the schematic so I understand how it works? A very very ...
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1answer
151 views

What resistors do I need for a simple LDR triggered h-bridge?

I am attempting to build this circuit: https://www.instructables.com/id/H-Bridge-on-a-Breadboard/ But instead of switches, I want ldr s like this circuit: https://www.instructables.com/id/Simple-...
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1answer
51 views

Light Sensitivity Indicator (using transistor, LEDs, LDR)

I have; 1) 9 V dc source 2) two LEDs (red and green) 3) LDR 4) few resistors (kilo ohm) 5) npn transistor I need to build a circuit such that the red LED lights up only at night (0 light ...
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2answers
119 views

NE555 LDR threshold voltage

The problem is that when I set the LDR on my car and stop for a short time near street lighting my headlights from the car are switched off. I made a circuit simulation, when I click 4 times for the ...
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1answer
742 views

555 timer delay circuit + light sensor?

I am quite new to electronics and I would like to combine these 2 circuits together so that during complete darkness on the LDR, the LED would turn on instantly and when light falls on the LDR there ...
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1answer
102 views

LPC1768 - Green LED when LDR sees light, Red LED when LDR is covered

I have been trying to achieve a task I am working on and I believe I am almost there. It successfully changes colors whenever I cover it but when it does, the red LED keeps blinking instead of it ...
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1answer
64 views

LDR breaks over time what to do?

http://cactus.io/hookups/sensors/light/ldr/hookup-arduino-to-ldr-sensor I have the following circuit which was running for a long time but at one point something broke and it started producing high ...
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1answer
541 views

NE555 and LDR circuit diagram

I have modified a schematic for my project with the following image: Instead of a 20K potentiometer, I use 100K for more precise adjustment. Do I need to add a disk capacitor of 10nf or 100nf to Pin ...
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1answer
60 views

How to find the best way to fade in/out?

I have a bunch of these PAR lights below. They work with DMX and have per LED PAR 3 red, 3 green, 3 blue and 3 white LEDs. I can set the value for the red, green, blue and white lights independently (...
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1answer
196 views

Voltage divider for ADC

Can anyone tell me why we use a voltage divider circuit with an LDR for an LDR robot? For example, why can't we directly take the LDR output and feed it to the ADC port in an ATmega controller? Why ...
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2answers
1k views

Calculating resistor values for a Schmitt Trigger and LDR circuit

I am trying to make a light sensing circuit which has hysteresis. I want an op-amp (LM358) to output logic 1 (12v) when the light level rises above 250 lux, and output logic 0 (0v) when the light ...
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1answer
53 views

Energia/MSP-EXP432 Issue: Analog In Pin removing voltage from Voltage Divider

In the circuit below, I want to measure the voltage going to the ADC (output from the voltage divider consisting of a fixed resistor and photoresistor) using an MSP-EXP432; however, the MSP-EXP432 "...
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1answer
141 views

MSP-EXP432 “Analog In” pin taking voltage from circuit [duplicate]

I am building a circuit consisting of a voltage divider (with a fixed resistor and a LDR or photoresistor) outputting voltage to an ADC. I want to measure the voltage going to the ADC using an MSP-...
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1answer
139 views

The 7-segment LED display is too dark when connect to a auto dimming circuit

I'm using the below circuit to build a auto dimming circuit. I was fine when I only use one 7-segment led, but when I connect more 7-segment led (parallel to L1) the light intensity is very low. How ...
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2answers
75 views

Device that transmits signal to computer [closed]

How would I be able to send a notification or email/msg of some sort to my computer after an event has taken place from elsewhere. To be more specific, when a tripwire is tripped, (LDR/Laser beam) how ...
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1answer
2k views

Please help me understand the following light-controlled relay circuit

I used the following circuit to control the outdoor light, and it works as I wanted. I am trying to understand the circuit and it looks like a comparator circuit, but I don't understand the use of ...
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2answers
178 views

Measure laser with photoresistor (LDR)?

I want to make a simple setum, where I can measure the opacity of air. I want to use a simple laserbeam, which I shoot across the room, and on the other side I want to measure how much is blocked/...
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0answers
234 views

How to identify different LDR photoresistors that have been mixed together?

I purchased a variety pack of LDR photoresistors from eBay which includes GL5506, GL5516, GL5528, GL5537, GL5539. The problem is that they all came in the same little bag and are visually identical. ...
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1answer
467 views

How to use multiple LDR to trigger a led? [duplicate]

Whats the best way to use multiple LDRs to power up an LED? Currently I’m using one LDR which turns on an LED when it senses light. But now I want to use three LDRs (at different locations) to trigger ...
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2answers
79 views

Light-activating a motor [duplicate]

I have an LDR and it reads higher than 17K ohm when the lighting conditions meet my requirements. I wish to be able to activate a vibrator motor (coin type 3 Volts) when the LDR has a resistance ...
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1answer
236 views

Arduino and car's 12V switch

I'm trying to control my headlights with my Arduino and a LDR. For this I will use the Arduino as a middle man between the lights switch and the actual lights. The switch has three positions OFF / ...
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2answers
350 views

Chicken coop door opener circuit

I'm designing a circuit that will open a chicken coop when the sun comes up. I've attached a bungee cord to the door which opens the door when a pin is released. This pin is released by a car door ...
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2answers
369 views

LDR issue interfacing with ADC [closed]

simulate this circuit – Schematic created using CircuitLab I want to read the voltage values of LDR (0-5V)but my desire range is less ( 1-3V) through ADC of 10-bit,but i am getting Clipped ...
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1answer
86 views

Understanding the circuit

I am a beginner electronic student and I know this might sound a bit easy for most of you, but I would like to understand the role of the components used in this circuit - it's an LDR-Controlled DC ...
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4answers
576 views

How does this LDR controlled light work?

Consider: The circuit here works based on the resistance of the LDR. I don't understand how it exactly works. It's said when the resistance in the LDR is high, current flows through R2 and the base ...
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2answers
276 views

Draw a circuit with a voltage divider, two comparator ICs, LDR sensors

I got this last question to practice for my exam and I got stuck. The question is draw a circuit with a voltage divider circuit, two Comparator ICs, LDR(Light Dependent Resistor) sensor Outputs: ...
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1answer
456 views

Use of transistor for switching the led

I have been trying a lot to get my circuit work. I want the led to light up when the LDR receives no light and vice versa. I have found that the LDR offers the resistance of approximately 6k ohms when ...
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2answers
380 views

Can I use a capacitor to power an Arduino for 5 minutes after the power has been cut?

I'm working on a simple setup using an Arduino Nano to automate the switching of my car headlights when it gets dark. I am happy with how to program the Arduino & LDR use and coding, it will be ...
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1answer
35 views

Photoresistor Night Switch

I have a problem regarding the schematic from the link below. I made the schematic from this link, at figure 5:http://www.nutsvolts.com/magazine/article/light-sensitive-circuits The problem is that ...
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1answer
515 views

Light Activated Switch Circuit with delay

In reference to this circuit: Photoresistor snap-on/off switch. If I wanted to add a small delay so that the circuit doesn't immediately turn then and off if the ambient light temporarily dips below ...
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1answer
863 views

Can LDR be affected by temperature?

I have an outdoor setup with arduino monitoring light sensitivity to turn on and off some lamps. https://diyhacking.com/arduino-ldr-sensor/ This started misbehaving couple of weeks ago and I wonder ...