Questions tagged [light-sensor]

The Light Sensor is a passive devices that convert this “light energy” whether visible or in the infra-red parts of the spectrum into an electrical signal output.

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2answers
87 views

Is there a way to measure or infer the color of a material from a distance (~2m), without using visible light?

I've recently started working on a graphics/SLAM project. We've encountered a problem that requires us to measure or infer the color / spectral reflectance (and ideally albedo) of points on objects in ...
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5answers
2k views

Thin wall to block LED light from hitting photodiode?

I'm designing a small heart rate sensor using green smd LEDs and a photodiode. The photodiode needs to measure the reflected light, and not direct light from the LEDs. The LEDs are near the perimeter ...
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1answer
42 views

IR Light Transmission Delay Error

The following circuit consists of two IR (Infra-Red) LED diodes; one as light transmitter (IR1) and other as light receiver (IR2). They are spaced for approximately 4 cm, so distance is not the issue ...
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1answer
148 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
61 views

How to filter out certain wavelengths of light [closed]

I am trying to filter out certain wavelengths of light and I was wondering if there is a way that you can filter them out. I am using Silicon Photomultipliers (Linked below) and I only want to detect ...
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2answers
84 views

Light sensors sensitive enough to detect for PWM from CF and LEDs?

I have an extreme sensitivity to PWM light sources such as computer screens and light bulbs. This can make it very challenging to make a purchase as I end up having to do lots of guesswork with ...
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0answers
45 views

How to deal with specular reflections from ultrasonic distance sensors

I am currently challenged with the following problem: I am given an autonomous robot which uses the HC-SR04 ultrasonic distance sensor to determine its distance to the robot driving in front. ...
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3answers
84 views

dc voltage control for LED lights?

I'm looking for a little bit of help on a project I'm working on. I need to find some way to make led light bars (18w and 120w) to automatically start out dim and gradually brighten to full ...
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2answers
130 views

Very low current (<10 microamps) darkness detector circuit that turns off in light

I've made a device that lights an LED at a very low current (<10 microamps) as a very dim indicator for use in the dark. At its simplest, the circuit is a 3V coin battery + resistor (300K-1M ...
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1answer
29 views

Phototransistor and Photodiodes capacitances when some in an array sense light

I'm using phototransistors to sense low speed data (about 7 bits a second). With one phototransistor and a 300K resistor, I found my sweet spot and can transmit correct data with lazer. I find if the ...
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0answers
32 views

Choosing a camera for near-infra-red illumination analysis

Which parameters are important to look for in camera specs./data-sheets if it will be used for irradiance pattern analysis from near infra-red sources. Typical spectra range of interest is from ~700nm ...
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1answer
69 views

Need a sensor for detecting the presence of someone like a door sensor we have in lifts/elevators

Door sensors used in elevators/lifts are very expensive and my budget is not that much. But I need a similar mechanism or solution to detect the presence of someone if he/she is standing in the given ...
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1answer
98 views

How to connect a 2 pin photodiode?

Initially, I have used 3 pin photodiodes, where the anode is connected to the resistor and has a wire which goes to group and the other goes to an analogue input to read the voltage. The cathode is ...
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4answers
1k views

How to tell how sensitive a photodiode is?

I am looking to buy some new photodiodes for a project. Currently, I have been using expensive photodiodes with a picosecond level rise and fall time and a very small area to pick up light. The ...
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1answer
67 views

Ultraviolet sensor response curve

I did a search on "ultraviolet sensors" in this forum, and came up with only three results, so, it appears, that this has not been asked before. I have a hand-held ultraviolet light sensor from ...
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2answers
80 views

Photodiode in photoconductive vs photovolatic configuration

I want to use a photodiode to measure light intensity, but I am not sure if the photodiode should be used in photoconductive or photovoltaic mode. From my understanding the photovoltaic ...
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2answers
168 views

VL6180X ALS values soo small

I have bought VL6180X proximity sensor on breakout (Aliexpress) originally designed for use with arduino. I have tried it use with Raspberry Pi and STM32 (on STM32F429 discovery board). Sensor is in ...
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3answers
451 views

How fast can we measure using IR sensors

Supposing I have an repeatedly object passing through IR sensors and I am looking at the output waveform. What is the maximum frequency the output waveform can have? I think this maybe related to the ...
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1answer
282 views

Which one is better to build lux meter, either LDR or photodiode?

I want to add the lux meter to my application. My controller works with 3.3V and ADC max reading voltage is 1.2Vref. I tried with LDR but I'm not able to get accurate values and the values also not ...
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1answer
236 views

Sensor to distinguish between daylight and artificial light in a room?

is there a way to distinguish between daylight and artificial light in a room? I'm thinking my options are a light intensity sensor or a color temperature sensor. The sunlight is supposed to be much ...
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1answer
50 views

Day-Light Sensing LED Light [closed]

I am looking for an example of a day-light sensing LED light, similar to https://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/ but instead of turning on when dark, I ...
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1answer
95 views

Relative responisivity of the VEML6040

I'm currently working a project involving the VEML6040 color sensor (Link to application note). I am reading through the application note and stumbled on the graph depicted below. As far as i ...
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2answers
71 views

How to measure body temprature and HBR with just one IR transmitter and receiver

I want to measure body temperature and heartbeat rate only with a IR receiver and transmitter. How could I do that? Is it an accurate method? Or I have to use IR temperature sensor for this.
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1answer
56 views

How can you figure out what encoded signal my IR emitter should put out to register a hit on a laser tag gun?

I am using a 38kHz IR emitter, I've taken out the IR receivers on these guns and experimented to see if I am able to transmit a signal, it's working fine, however when I connect the IR sensor back in, ...
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3answers
271 views

How to control the brightness of an AC light bulb with the instant level of noise nearby

The device I want to make is simple to describe: a big red lightbulb, connected to the AC 110 / 220 V, stays dark when it's quiet in the room, starts lighting up somewhat if there's a moderate level ...
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1answer
78 views

Why popular line detection use Infrared(IR) based sensor? [closed]

Popular line sensor use IR LED as transmitter and IR photodiode as receiver to distinguish reflective color such as white and less reflective color like black. Consider that infrared LED is hard to ...
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2answers
152 views

Switch triggered by flashing light

I'd like a simple switch that triggers when a flashing light is detected. Purpose is to open gate by flashing car headlights (say 3 times). I have looked at comparators and photoresistors and ...
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2answers
64 views

Simulating a pyroelectric sensor

I am building test rigs and need to trigger motion detectors remotely. I would also like to avoid using a light source. The devices I've encountered all use an Excelitas 968 pyroelectric sensor (http:/...
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3answers
115 views

Lux sensors with max. operating temperature of 90-100 deg C?

For my project, I need to observe the lux inside a double-pane window. Last time, I used 'Adafruit TSL2561 Digital Luminosity/Lux/Light Sensor Breakout'* but its recommended maximum operating ...
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1answer
168 views

Kid's night light

I would like to make a more reliable nightlight for my daughter. I was using cheap solar string lights but they just don't last long enough or get enough sun on that side of the house. So I've ...
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3answers
177 views

Reference for color sensor [closed]

I am trying to make a colorimeter using TCS3200 sensor and white LED light source. After weeks of research and understanding on how different white light sources work and what are the algorithms ...
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2answers
1k views

Dark sensor using relay

Trying to develop a dark sensor. Have successfully made it but with a major problem. As you can see the circuit here: When the LDR is covered the LED lights up using the relay NO terminal. However ...
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1answer
96 views

Will I detect any signal if I apply laser light on one of the two light sensors placed in a sunlight?

I am trying to make a counter which should work in a solar light. I am thinking to use two ambient light sensors placed close to each other and use a differential amplifier. One sensor receives a RED ...
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4answers
286 views

LM393: Electronic Fry Counter

We're using an LM393 Light sensor and a laser transmitter used for counting the fry that will enter into our machine. The machine counts properly when we use an object like a pen or a stick in front ...
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2answers
76 views

Is it possible to detect specific UVB wavelength ranges using just a UVM-30A UV sensor or similar

Is it possible to detect specific UVB wavelength ranges using just a UVM-30A UV sensor or similar. The spec sheet for sensor GUVA-S12SD. Seems to indicate that it generates a specific current level ...
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4answers
456 views

Is there a light sensor that varies output with wavelength?

What components are sensitive to the wavelength (energy) of impinging light? I am wondering if there are any that have a reliable and detectable response to wavelength instead of just intensity. For ...
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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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2answers
521 views

Are light dependent resistors stable wrt time?

This question specifically concerns my issues with an ORP12 like:- I've read the data sheet and I see that resistance changes wrt short time (15 sec). Also note 1 mentions 16 hours. But what happens ...
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2answers
234 views

Using multiple white LEDs to obtain a unique CCT

I need to swipe between two white shades from one to another color temperature, let's say from 2700K to 6000K. Can it be done by simply mixing the intensities of two LEDs of respectively 2700 and ...
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3answers
481 views

How to build a light sensor for PWM dimmed light (for comparison against CC dimmed light)?

I am working on a project in which I need to find a PWM duty cycle to dim an LED to the same brightness level as an LED being dimmed with CCR. Initially, I was considering using a camera for this: I ...
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5answers
702 views

What's causing a bad response time of a phototransistor at 100 Hz

I am working on a project that involves communicating with LEDs. I need to be able to detect the state of a light source that is flashing at about 100 Hz. I am using the phototransistor that comes ...
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2answers
569 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
946 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
79 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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1answer
6k views

Is it possible to replace a two way switch with two wall PIR sensors? [closed]

I have a two-way switch for the lights on the staircase and I want to replace them with two-PIR sensors. I received the sensors yesterday and I discovered that they have only two wires and I am ...
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2answers
765 views

Can I use the IR break beam sensor outdoor/indoor for 4-5 meters range?

I need a sensor which can count a fast moving object. I am thinking to use IR beam break sensor. But, I think there will be a problem with the sunlight as the Tx-Rx will be 4-5 meters apart. I also ...
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2answers
223 views

Photodiode robust enough for laser?

I want to detect a laser using a normal photodiode (Datasheet), but I am not sure whether it is robust enough, as laser (lower than 5mW) emits high energy photons. Can I shine on such a photo diode ...
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3answers
598 views

How to avoid LDR controlled light self-latching?

I am planning on using an LDR to turn on a LED light (700 lunes warm white fixtures), when the main light in the room gets turned on. But this LED light is pretty bright on its own. I think I will end ...
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0answers
2k views

How calibrate an RGB LED to get correct color mixing [closed]

We are using RGB LEDs in our product and we require to emit white light to indicate a certain state. But because of the tolerance of the resistors and the LED itself it is hard to achieve the same ...
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1answer
395 views

opt 101P photodiode for light communication [closed]

The following is the circuit for Light communication using opt 101P photodiode. Connections are COM pin (pin 8), and pin 3(-V) are grounded. Input volatge(pin 1) Vcc = 9 V . OPT 101 has a photodiode ...