Questions tagged [photoresistor]

A photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor.

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3
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1answer
111 views

Using op-amps to read real-time resistance values over a wide range

Background I have been using a simple inverting op-amp circuit and Arduino to measure the resistance of a photoresistor (light 5k, dark 200M), like in the schematic below. This provides linear data ...
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4answers
207 views

Why do LDR photocells use CdS and CdSe?

Basically what the title says. Cadmium is a toxic, environmentally harmful heavy metal that's banned under the RoHS directive, and even before RoHS its toxicity was well known. What makes cadmium ...
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3answers
2k views

Understanding basic photoresistor circuit

I'm new to electronics, so I just can't wrap my head around how this photoresistor circuit works. I understand the following: the photodiode can be understood as a variable resistor (i.e. works in ...
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1answer
77 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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0answers
195 views

PV cells (photovoltaic) I-V curve plot simulation

I am trying to plot the I-V curve using python because that helps me in understanding PV cells / solar panels (and diodes as a general thing). I know the formulas ...
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0answers
60 views

phoresistor vactrol tremolo noise

I made an optocoupler by shrink tubing a generic photo resistor and a cold white led. Then used it in the following setup to be able to control audio level to achieve tremolo effect: simulate this ...
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1answer
117 views

how to wire together multiple photoresistors to make one big sensor?

I'm using an esp32 dev board, and a bunch of 5v laser diode emitters pointed an equal number of photocell resistors across a plane. The goal is only to detect when any two or more beams break at the ...
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0answers
139 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
71 views

Reduce active region of NPN transistor

I've got a small LED garden lamp, battery operated, that turns on with a switch. I am currently trying to use a photoresistor that I have to make it turn on when it gets dark (so I don't have to ...
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2answers
383 views

Solar powered LED via capacitor?

I am building a large garden peice in wood, which I hope to illumine from within, powered by a small, (perhaps 90x65, 6v, 0.6w 100mA as space is limited) solar panel. After testing, I noticed that ...
5
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1answer
1k views

Is my IC broken?

I'm making my first circuit for a line following robot. I already made the prototype, soldered it together, and now I'm at the assembly stage. Here is the circuit diagram I'm using: What should ...
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5answers
179 views

Photoresistor power switch for arduino, does this look correct

edit: uploaded schematic: I am a novice, this diagram may not be correct but should convey the attempt. I want to turn-on power to an arduino microcontroller when it is dark. I white-boarded an ...
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1answer
84 views

PCF 8591 switch using transistor

I'm using a PCF 8591 ADC for the sake of the photo resistor on it - here. The project doesn't seem too complicated for a software engineer like myself but I seem to need some help. I'm using an ...
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1answer
226 views

Photo resistor night light not working

I am completely new to this stack exchange and to electronics and general so please keep that in mind if my question is not up to par for this site. I've attempted to make a night light using a ...
0
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1answer
60 views

Night Activated Switch

I draw a schematic which uses LM741 and IRF830. The main function of the schematic is to light up a few leds (which consumes about 100mA in total) when the night comes. Please have a look at the ...
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4answers
146 views

Arduino sensor data erratic

I'm a noob just getting my feet wet in EE, so go easy on me, please. I bought an Arduino Uno and have been learning tons in the last couple weeks. I took an LM35 sensor, a generic thermistor (using ...
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2answers
315 views

Photo resistor is giving off an unsteady output, how can I fix that?

I just started out with Arduino, and for my first project, I need to use a photo resistor to get an accurate reading of ambient light in my room. Problem is, the photo resistor is not giving off a ...
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3answers
107 views

Toggle “on/off” with small resistance change

I'm trying to make a small model car stop when it crosses a black line on the ground. My idea is to use a photresistor + some magic to do the trick. I'm here for the magic part... The resistor I have ...
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1answer
3k views

How to increase sensitivity of Light Dependent Resistor (LDR) [closed]

I am using LDR sensor in my project. The source of light comes from the different colour of images. As we know, the spectrum of each colour is different and it will produce a different intensity of ...
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5answers
371 views

Transistor Collector Heats Up

I used power transistor to drive high power LED (used in streetlights) I added resistor between the Transistor Collector and the LED to verify which part of the transistor causing too much heat, and ...
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3answers
200 views

Clean water turbidity sensor

I'm working on a project to determine the water clarity, using a MCU with a turbidity sensor. I have tested sensors such as: Cheap Dishwasher sensor, and while it works for changes in turbidity in ...
1
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1answer
343 views

Photoresistor Transistor Circuit

I am teaching myself electronics. I designed this circuit to use a photoresistor to trigger a transistor when I hit the photoresistor with a laser pointer. On the Arduino side, I want it to look like ...
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1answer
389 views

Trying to find transistor needed for laser security alarm

so I'm building a laser security alarm circuit for a class project and I need a transistor, but I'm having difficulty figuring out what type to get to allow the circuit to switch ON/OFF once light is ...
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2answers
225 views

Photo Resistor to Complete Circuit in Light

I am trying to create a very simple circuit using a CDS photo resistor. The situation is simple, I need a circuit to be connected when its light, disconnected when its dark. The photocell will sit ...
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1answer
305 views

LDR / photoresistor issue: resistance is constant in different light conditions

I have installation with Controllino mini, it's essentially an ATmega328, and with 6 LDRs and 6 lasers, creating laser rays/barriers. The system acts as a lasers labyrinth for entertainment purposes, ...
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1answer
273 views

Photoresistor with NE555

I would like to build a circuit with two blinking LEDs using a NE555 timer and a photoresistor. In the schematic below the blinking frequency becomes higher when more light shines on the photoresistor ...
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0answers
129 views

Why does inside of my sphere appear to be getting darker?

This a fully enclosed sphere containing a web cam, white led and photo resistor in exactly the geometric arrangement shown. The led glows dimly (via fixed dropper resistor). It runs at about 9 mA. ...
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2answers
2k views

Confusing dark sensor circuit diagram

I recently bought a set of four "light-control sensor switch" from ebay (link). Circuit diagram below. I put the circuit together (it was a DIY kit) and connected a protected LED at the output. The ...
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3answers
867 views

Read LDR with A/D converter with adjustable senstivity

I'm working on a small project, where I read up-to 12 brightness values from light dependent resistors (my schematic below only shows three). The basic layout is a voltage divider per sensor, which is ...
2
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1answer
78 views

Low Current Sensor Reading

I'm having a very hard time trying to read and keep a low current draw from my sensor which is FSR-402: https://www.adafruit.com/product/166, but to help others, this can also be a problem with photo ...
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2answers
587 views

ESP8266 detect LED flash with photoresistor Schmitt trigger?

I made some experiments with ESP8266 to detect when an external LED is on or off (I need to log this activity). This is the test-circuit I used till now: simulate this circuit – Schematic ...
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1answer
983 views

Which is best way to detect external led flashing with ESP8266 keeping circuit power consumption very low?

I have an external led (color is red) which flash with variable frequency. I need to monitor those flashes, calculating how many time led flash in a minute and log them. I made a first try with an ...
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1answer
82 views

How do I build a micro controller based laser detector

I want to build a laser detector using a photoresistor and a pen laser. Ideally, I would like to increase the surface area that detects the laser beam, perhaps through refraction or diffusion. I'm ...
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3answers
3k views

Why is it “Vactrols” are not commonly used?

I've been trying to get my hands on some Vactrols (opto-variable resistor) for a long time, unsuccesfull. Not even digikey has them. some examples: VTL5C2,VTL5C3,NSL32 Can't see them as "too ...
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3answers
1k views

How to wake up ESP8266 with light change?

I want to send information to the server when the light changes (turns on or turns off). As for now, I have a photoresistor connected to ESP8266's ADC pin. I'm measuring voltage and sends information ...
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2answers
1k views

Photoresistor LDR in parallel

I need to sense light in 50 different points, but i can only arrange them in parallel because i need to use only 2 wires (this is limited by the application constrains). I only need to know if any ...
0
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1answer
4k views

S8050 D331 base resistor calculation

I was trying a basic transistor circuit to understand transistors (LED on the collector without a base limiting resistor ). Now on to the next step, to know where and when to put what values of ...
0
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1answer
599 views

Convert varying voltage to resistance

I'm just beginning with electronics, with the goal of building synth and audio effect modules. I'm currently building and tweaking projects from http://tagboardeffects.blogspot.co.uk. One mod I'm ...
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2answers
464 views

using a photoresistor as a control of speaker

I got a project to show a group of kids in the community center with some circuits. I am not majoring in EE so I will instead to show something simple. I borrow a snap circuit kits and I am going to ...
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1answer
105 views

Comparator Question (and more general question)

I have been fascinated with electronics my whole life and read many books on it, but only recently have I began to really tinker, and I have often been befuddled by many salient details that are ...
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3answers
918 views

Best way to amplify the photoresistor signal

I have the following schematic. simulate this circuit – Schematic created using CircuitLab And it graphs to an almost stratight line. It is supposed to be a heartbeat sensor. From what I have ...
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3answers
1k views

How to use photoresistor for counting passing objects

Can photoresistor be used for counting passing objects?## Heading ## Hello i'm new to the electrical things I wanted to ask if i can use the photoresistor sensor for counting passing objects if yes ...
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2answers
2k views

Choosing resistance in series with a photoresistor for best light-measurement resolution

simulate this circuit – Schematic created using CircuitLab I have a photoresistor, R1, and as a voltage divider a fixed resistance, R2. There is a voltage of 5V over these two, and the voltage ...
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2answers
2k views

High voltage voltage controlled linear variable resistor

I have some high voltage (300v+) analog circuits that I want to control digitally which requires the use of a voltage controlled linear resistor that can withstand the high voltages. I don't expect ...
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4answers
3k views

Why do I have to use an additional resistor with a photoresistor?

I'm totally new to electronics and I wonder why we need to put a resistor in series with a photoresistor to measure the variation of light? I mean, photoresistor is already a resistor, why do we have ...
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2answers
149 views

Is there a certain type of LDR that will be most effective in a circuit that senses the heartbeat at a fingertip?

I haven't had much experience with LDRs, and was not sure of the different types that will work best in a circuit like that.
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1answer
2k views

On/off circuit using photo-resistor (LDR)

I am not afraid of the work but do not know how to do the math to calculate what I need for components. I am trying to create a photo resistor circuit to control some LED model street lights. I have ...
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2answers
83 views

Photoresistors detection

If I have a 2cm*2cm square and drill a really small hole in the middle thats barely visible for the human eye, and I place a photoresistor below , will the photoresistor be able to detect any light ...
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1answer
166 views

My previous theory was wrong, so why does this work?

Hi I am new to electronics, and I have made a light tripwire using an Arduino Uno. I made this on the idea that electricity follows the path of least resistance, which I now know to be false (https://...
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1answer
145 views

Having trouble with light activated circuit.

R1 = 10K 1/4W Resistor R2 = Photoresistor (any type) R3 = 2M2 1/4W Resistor R4 = 1M 1/4W Resistor C1= 10µF 25V Electrolytic Capacitor C2 = 100nF 63V Polyester Capacitor D1 = 1N4148 75V 150mA ...