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Questions tagged [photoresistor]

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

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Solar Array Control With Photocell

We did search on this topic before making this post, but this is as close as we found; Link to question from 2020: Solar Panel-Photocell Wiring ... which didn't seem to be closely enough related to ...
Stephen Falken'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
2 votes
1 answer
74 views

How to bright up LED when it's dark without wasting battery energy?

I am trying to design night light LED that brights up when it's dark. I know a solution using transistor that "drains" current so LED has not enough to light up. A current flow through ...
eSeverus's user avatar
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Shadow-triggered LED fade circuit

I'm making an interactive art project and I'd like to have an LED that turns on when someone puts their hand in front of a light sensor (photoresistor). I got that working. Next step is that I'd like ...
monkbroc's user avatar
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4 votes
1 answer
537 views

How to prevent photoresistor sensor from draining battery

I'm looking for a simple hack to minimise current when detecting change in light intensity using photoresistor. I'm using ATTiny85 in deep sleep (power down, ADC disabled, using below 1 microamp) ...
PanJanek's user avatar
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3 answers
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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 ...
Ljuslykta's user avatar
-1 votes
1 answer
161 views

How to test photo interrupters

I have come upon two photo interrupters in a calibration kit circuit. The circuit seems to not respond. How can I check these photo interrupters? The green LED is responding when an object is brought ...
Sujith's user avatar
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1 answer
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Ltspice: vary resistor

I wanted to simulate an LDR and a specific case where I have a bright LED using PWM. This is the schematic: I was changing the resistor as stated here which comes from a previous discussion ...
Tiago Ferreira's user avatar
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2 answers
173 views

Solving for closed loop current in photoresistor-transistor circuit

I am working on trying to relearn some basic circuit analysis and I am stuck on the attached problem. I have a circuit using a transistor and photoresistor to turn on an LED when dark. I have ...
Learning4Fun's user avatar
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Why will this circuit only work if it is assembled live?

Updated Schematic picture. Some components (power supply, other things connected to the MOSFET) are omitted. The ICSP header was kept since I think it may be interfering somehow. I have an ATTiny84 ...
Lorenzo's user avatar
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How to choose a phototransistor or photodiode?

I've found a photoresistor (yes, resistor, probably 30 years old) in my scrap box, attached it to an ATtiny as ambient light sensor, with a 100kΩ resistor as voltage divider towards +5V. On power on, ...
stefan's user avatar
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In this circuit, the light intensity sensor (LDR) only senses 3_2 cm. How can I improve the sensitivity of this sensor to reach 1m?

In this circuit, the light intensity sensor (LDR) only senses 3_2 cm. How can I improve the sensitivity of this sensor to reach 1m? https://ibb.co/c3X1NRS
Forkan Xa's user avatar
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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More current in non-inverter comparator hysteresis using a photoresistor

I'm doing a small circuit where I need automatic LED's to turn ON in a low light environment. So I decided to use a photoresistor (more light less resistance) connected to a non-inverter hysteresis ...
Bikke21's user avatar
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Two different LDR circuits: what's the fundamental difference?

Here’s what’s going on. I’m working on a programmable light timer (of course I could use something like Alexa, but I’d rather go for the challenge and build something to my own design), where the LDR ...
Mike's user avatar
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2 answers
777 views

How to calculate value of voltage by light intensity?

I want to write the code to turn the LED on when the light intensity that falls on the photoresistor decreases. So in daylight LED is off, and when it's getting dark LED goes on. I know that ...
cerouno's user avatar
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-1 votes
1 answer
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Determine the output voltage of a signal conditioning module

Already, apparently from the feedback I got from this: How to model the output signal of this circuit? It is better to just explain the whole thing. I am doing a project involving a LDR sensor that is ...
Granger Obliviate's user avatar
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2 answers
95 views

How to model the output signal of this circuit?

Following up this question: Thévenin equivalent: is this resistor useless? I've now changed the voltage source to a resistor since this is a photoresistor. However I have no idea now how to ...
Granger Obliviate's user avatar
0 votes
3 answers
691 views

Dark sensor with transistor

Why do most of dark sensor circuits in the Internet look like this? It seems to me that in such circuit, photoresistor doesn't limit base current and it doesn't work. I think that photoresistor ...
Maciaz99's user avatar
0 votes
5 answers
1k views

How to estimate the recommended current in an optocoupler?

I intend to use an optocoupler to simulate a push button on a control card (I could measure 5V between pins but I don't know for sure if there is a pullup resistor in the card). Also the other way ...
aherve's user avatar
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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 ...
Piotr Czerwonka's user avatar
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1 answer
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Circut to turn on a battery powered electric fence

I want to be able to have a battery powered electric fence automatically turn on in the morning when it's day light, and power off when it gets dark. I don't seem to be able to find a product that ...
TheSilverback's user avatar
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2 answers
291 views

Photosensitive Diode or photo resistor?

As I understand it, a photosensitive diode generates a small current with light. I ordered these off Amazon: https://www.amazon.com/gp/product/B01F3TU2XC/ref=ask_ql_qh_dp_hza These change resistance ...
Tim Duncklee's user avatar
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Photoresistor audio switch on battery power

I'm trying to build a light-driven chime silencer for a wall clock. The schematic from https://electronics.stackexchange.com/a/177401/18259 seem like a very good starting design for this: It, however,...
Rob Napier's user avatar
1 vote
2 answers
450 views

Confused about the functioning of a QRE1113 reflectance sensor

First year IT student here. I've been stuck on a problem involving a QRE1113 sensor, in which we were given the schematics below: From my understanding so far, the reflectance sensor is divided into ...
Solaris2345's user avatar
2 votes
1 answer
838 views

Accuracy of manufactured photocells (LDR) with respect to light intensity

I was looking through photocell (photoresistors) datasheets, like for instance the NORPS-12, especially the graphic on resistance value versus light intensity. In no datasheet could I find information ...
vava's user avatar
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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
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1 vote
1 answer
78 views

How do I make a high signal last longer so my nodeMCU/Tasmota sees it?

Problem I have a data input signal to a nodeMCU running Tasmota. It only works intermittently because the signal often isn't high long enough for Tasmota to sense it. So I need to find a way to make ...
pinoyyid's user avatar
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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
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2 answers
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Design review for photoresistor-controlled linear regulator

I would appreciate some comments/insights/criticism on my design: I want to turn on/off a linear regulator (MIC5504) based on the light. I have tried just using a resistor and photoresistor voltage ...
Ozbekov's user avatar
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2 votes
1 answer
293 views

Is there constant current flow in this circuit?

I am studying basic circuits, and have a very elementary question. When the photoresistor is exposed to light in the following circuit, is there a constant drain on the power supply? If this were used ...
Ben's user avatar
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0 answers
139 views

Photo-resistor and leds

I'm trying to build some system that would detect light and turn a 12v led strip ON. The only power that I have available is a 9v battery. I found some Arduino compatible boards but it seems overkill ...
Georges Legros's user avatar
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108 views

Light sensor connected to GPIO input of raspberry pi

I have created simple light dector. Schemea is below: Real circuit on breadboard: I have written code in python using GPIO library: ...
Krzysztof Michalski's user avatar
1 vote
2 answers
232 views

Light detection by GPIO raspberry pi

I have a cirtuit which consists of Resistor, Photoresistor, PNP Transistor, Voltage supply from raspberry pi like on the schema below: Purpose of this circut is to detect light as a dawn detection ...
Krzysztof Michalski's user avatar
3 votes
1 answer
98 views

Radioactivity counter

I am designing a Geiger counter which measures radioactivity. I am planning to this using the photoelectric effect. The band gap of insulators is pretty big and only gamma particles are energetic ...
McCarter's user avatar
0 votes
2 answers
841 views

What options exist for a for low-latency (<1ms) photosensor?

I'm wanting to build a computer keyboard-to-display lag measuring tool using an Ardunio: User places the photosensor right-up to their computer monitor. User presses a button on the Ardunio. The ...
Dai's user avatar
  • 143
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1 answer
120 views

Reading full photocell range with ADC

I am trying to use PDV-P8103 photocell as a sensor for LCD dimming circuit. The application requirements are to have comfortable brightness level from almost total darkness up to direct sunlight. The ...
Maple's user avatar
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0 votes
1 answer
198 views

Proper phototransistor for detection of small object

I am attempting to detect a falling objects 6mm in diameter, falling every 160ms. The object to be detected will be confinined to a black tube, void of light, 18mm wide x 35mm long, my plan is to ...
J Sera's user avatar
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0 votes
1 answer
186 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 ...
Scott Wood's user avatar
1 vote
1 answer
1k views

Convert a Dusk-to-dawn outlet device to Dawn-To-Dusk? [closed]

I recently purchased a Dusk-to-dawn outlet sensor (https://www.amazon.com/dp/B00002NB2X?ref_=pe_2640190_261118450_302_E_DDE_dt_1), but I'm wanting to convert this thing into a Dawn-to-Dusk device ...
dobbs's user avatar
  • 113
4 votes
1 answer
3k 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 ...
Liang Hao's user avatar
6 votes
4 answers
3k 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 ...
Hearth's user avatar
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7 votes
3 answers
4k 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 ...
user2305193's user avatar
0 votes
1 answer
387 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-...
J D's user avatar
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2 votes
0 answers
1k 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 ...
TPPZ's user avatar
  • 121
1 vote
0 answers
183 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 ...
Ben's user avatar
  • 139
0 votes
1 answer
649 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 ...
3z33etm's user avatar
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1 vote
0 answers
758 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. ...
Zhro's user avatar
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0 votes
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136 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 ...
Daniel Nabais's user avatar
0 votes
2 answers
2k 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 ...
Axe's user avatar
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