Questions tagged [photoresistor]

Light sensitive resistors whose resistance decreases with the amount of light they receive.

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1answer
30 views

10k Resistor for LDR [closed]

I'm quite confused, most of the tutorials i found regarding LDR, uses 10Kohm as a fixed value resistor for voltage divider in which they use Axel-Benz formula which is: Where: Rmin = 100ohm and Rmax ...
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2answers
64 views

Using a photo resistor to detect objects of a certain color

I am trying to build a robot that detects cubes of a certain color, and later picks them up. I was planning to use a camera and process the image, but I was told that Arduino is not capable of image ...
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1answer
360 views

Detect a camera flash? Light sensor, photoresistor?

I'm looking to build an Arduino-based "camera flash logger" to detect when a camera flash goes off, and maintain a log of those events. My thinking is to use a photoresistor to measure light level, ...
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1answer
51 views

Measuring lenght of time light levels peak using photoresistor

I'm trying to measure shutter speeds on old cameras. This essentially consists of: Shining a torch at one end of the camera putting the photoresistor at the other end trigger the shutter which ...
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2answers
778 views

Can I measure multiple photoresistors from one pin?

I would like to make a laser sensor to detect light coming from a 650nm diode. My current idea would be to use CdS photoresistors/LDRs. I want to measure a few (4-8?) at once, where light falling onto ...
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3answers
394 views

Photoresistor and another switch

I am using the circuit diagram below to turn ON/OFF the lights using Photo-resistor. How can I use the Arduino to bypass the Photoresistor effect? Let say I want to turn ON the lights even though ...
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3answers
1k views

Measuring time between two photoresistors and printing time on lcd

I am working on a project that is supposed to record the time difference between two photoresistors that are 4in apart. The photoresistors are sensing the passing of water or other liquids on a chute/...
5
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2answers
1k views

Detecting the light source location using multiple photoresistors

I am not an expert yet, so please forgive any possibly wrong terminology that I may have used. I am planning to place 6 light sensors in 1 meter (or maybe more) distance from one another, like this (...
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1answer
3k views

How to restart a counter in a program using a push button in a LDR Tripwire setup

So, trying to configure this code so that when I push the button, the person counter will go to zero and just as it goes, the counter will increase when the LDR will get tripped and again when the ...
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2answers
97 views

Photoresistor value drops when board stacked on Arduino Uno

I have a simple photoresistor displaying values on a serial monitor every second so I can establish a value that I want to use to have it activate a relay. It has worked fine for a few weeks, with ...
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3answers
201 views

Increase the resistance of a photoresistor with increase in light intensity

I'm building a laser tripwire of sorts and instead of shutting up when the laser points on it (which is essential for my project) it beeps louder. Here's the code int buzzPin = 11; // buzzer ...
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3answers
116 views

How can I understand the circuit diagram for Arduino Starter Kit Project 4?

I have acquired the arduino starter kit project book, and the explanations seem at times confusing and difficult to understand. Concerning the above circuit diagram, the book states (I am ...
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1answer
907 views

How do I adjust the scale/calibration of a photoresistor?

This photoresistor has a min/max of 0-1023. I'm trying to scale the brightness of a cathode RGB LED based on the sensor's value, but based on my current lighting, the min/max readings I generally am ...
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1answer
159 views

Photoresistor Switch

How would I use a photoresistor like a switch. My issue is it is always bleeding out a little bit of power and always on. Is there a way to connect it to a digital pin and when a resistance of xxx is ...
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3answers
2k views

How can I get my Arduino to recognize a specific object using some kind of sensor?

This is my first question on this site, and I'm relatively new with Arduino. I do have some experience using the board to reprogram a robot that used infrared proximity sensors, servos, and switches. ...
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1answer
48 views

Analogue input 0 staying at 0 when sensing light with Arduino and a photocell

I am doing a circuit for capturing light intensities. I followed the tutorial provided by Adil Moujahid Yet, when I plug the jumper wires on 5V the circuit stops working and when I plug on 3.3V the ...
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4answers
159 views

How can I use arduino board for AC mains?

I want to use LDR to control a light bulb (12W) which runs on AC supply using Arduino. Is it possible to do this? If yes, how?
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2answers
501 views

Why are my sensors not working (the reaction time is so slow)?

//testing the light sensor; int sensor=A0; // setting as input is by default; int sensorval; int pin=13; void setup() { // put your setup code here, to run once: Serial.begin(9600); pinMode(pin,...
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1answer
802 views

How to change LDR output in simulator 123D Circuits?

I used simulator 123d.circuits.io to create simulation of basic circuit with LDR: LDR is connected to 5V and via 10K resistor to GND. Wire between LDR and resistor is connected to analog pin where I ...
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2answers
2k views

Reading a photoresistor

I have a wire with a 0-5v current. I want to detect if the current is there or not (HIGH/LOW.) I'm using an optocoupler to avoid putting too much current into my micro, as it is only a 3.3V micro. I'...
2
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1answer
620 views

Analog INPUT_PULLUP for resistive sensors?

Can you use the internal pull-up on an ADC pin? Is it correct usage? Example of hardware usage would be a cadmium photocell between Ax and GND. Software is the same, except declaring Ax as ...
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0answers
35 views

How do I find which values are corresponding to the changing values from my phototransistor?

I am new to using serial input. I have an IR emitter and a photo transistor hooked up to my Arduino, I am trying to see which values corresponds to the colored object I put over my IR emitter and ...
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5answers
19k views

Why do you need a second resistor when using a photoresistor/LDR?

A photoresistor is already a resistor and will limit the voltage in the circuit. Why can't this be connected to a pin and measured? Why is a second resistor needed to connect the photoresistor to ...