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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7answers
1k views

Any better way to determine source of light by analyzing the electromagnectic spectrum of the light

Project overview I am tasked to develop a microprocessor based device that when shown a light upon, can determine the source of the light (Natural light, Flourescent Bulbs, LED Bulbs, Incandescent ...
18
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4answers
2k views

Night light, schematic and functioning

I recently bought an el-cheapo night light for $1 just to see how they manage to get the costs so low. I expected to meet an el-cheapo voltage regulator at best or even a bridge rectifier but alas! ...
18
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2answers
17k views

High frequency blinking LEDs and sensor for that

I want to make LEDs blink rapidly. (more than 1000 blinks/sec., faster is better) First, I am curious that the common off-the-shelf LEDs have a capability of blinking with such a high frequency. ...
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2answers
548 views

Understanding optical parameters of image sensors

I noticed that image sensor manufacturers provide some optical characteristics in different formats. I wish to know how to interpret that information. Sensitivity is characterized in \$\dfrac{V}{lx \...
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1answer
7k views

What Colors or wavelengths are Photoresistors sensitive to?

Using a LDR or Photoresistor, are they more sensitive to one color or wavelength compared to another? Or are they consistent with any light? Why?
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2answers
485 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 ...
4
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2answers
807 views

Are photoresistors reliable for light sensing applications?

I've used photoresistors for hobby projects before, such as this one: http://www.foxytronics.com/learn/electronics/kit-guides/starter-electronics-kit-guide/making-an-led-light-sensor However, now I'...
4
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1answer
71 views

Detecting solar reflections

Background: I have a hobby of heliographing (sending messages using reflected sunlight), and have a working setup that requires a human to adjust a mirror to follow the sun, interrupt the beam of ...
4
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2answers
2k views

Solar tracker Sensor arrangement

I am making a solar tracker and was checking different methods for Sun Light Sensing. This one is what I was going to use, which is pretty simple arrangement of LDR sensors, which go in shadow if ...
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4answers
931 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 ...
3
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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 ...
3
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2answers
829 views

Component to detect the state of an external LED

I need to detect the state of an LED in a machine that I cannot connect to in any electrical way. So I would like to measure the light emitted from this LED. The conditions: The ambient lighting is ...
3
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2answers
1k views

Image Sensor sensitivity

I am not sure what really the term "sensitivity" means when characterizing image sensors, so I will describe what I am looking for in the sensor at the following conditions: the exposure time is very ...
3
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1answer
721 views

Large photodiode capacitance

I'm working with an avalanche photodiode with a 320 pF capacitance. What exactly are the downsides of suc a photodiode with large capacitance values? I assume they would be slower due to the narrower ...
3
votes
1answer
97 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 ...
2
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3answers
2k views

Light activated switch - avoid flicker when turning on

I have a small light bulb (3W LED, E27/110V) that I am controlling using based on ambient brightness (it comes on when it is dark, and goes off when it is light). The circuit uses a BT136 triac, a ...
2
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2answers
219 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 ...
2
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2answers
573 views

Digital camera sensors and long exposures

Why do digital cameras need a long exposure time in low light conditions? Sometimes the exposures are 15-30 seconds or longer. Doesn't the electronic sensor achieve a steady state under 1 second or so?...
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2answers
81 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 ...
2
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2answers
524 views

8-bit console light gun trouble [closed]

I have recently purchased an 8-bit gaming console out of nostalgia, of course the light-gun that came with it did not work on modern LCD screens. Now I know that when you squeeze the trigger of the ...
2
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4answers
554 views

Long range directional light sensing

For an outdoor system I'm designing, I'm looking for a sensor able to detect a signal light from a distance of 50-150 metres and provide an output to a low-end microcontroller (i.e. not enough ...
2
votes
5answers
123 views

Suggestion for a lack of light warning unit when in motion

I would like to build a small device that warns me, with sound and or a 'dash' lamp, that my headlight is off if the motorbike is moving. My challenge is it is under warranty, so I cannot in any way ...
2
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3answers
108 views

improve IR reciever

I have simple IR receiver without any modulators, which reacts for IR wave (940 nm) link , I connected it as on this schema I beam on this receiver with laser diode with 650 nm lenght wave light. It ...
2
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4answers
207 views

How can I sense if a cane is being held upright or fallen down?

I am trying to make a little wireless-connected gizmo to attach to my grandfather's walking cane. The idea is that when it senses the cane has fallen down, it would alert/call one of us so that we can ...
2
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1answer
61 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 ...
2
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1answer
563 views

Detect the colour of an LED (Red Blue or Green)

I am trying to find a way of determining the colour of an LED without an electrical connection to it, i.e a sensor pointed at the LED. I can place the sensor quite close to the RGB LED I intend to ...
2
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1answer
163 views

How to measure relative light intensity (and ideally duration) of a xenon flashes, cheaply

I want to compare the light intensity (and maybe also duration) of multiple xenon flash designs. It does not have to give me the readings in any real unit, as long as it is linear (or mathematicaly ...
2
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1answer
644 views

Transimpedance amplifier bandwidth

I'm planning to use an Avalanche Photodiode (APD) to perform sequential light sensing - something around 100 readings under a minute. From my calculations this implies a frequency of around 1.67~2Hz. ...
2
votes
2answers
106 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 ...
2
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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 ...
2
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1answer
970 views

DIY laser range-finder

I would like to develop a laser range-finder board similar to Extech DT300. I would like to achieve a centimeter precision at 20 meters. I don't know if devices such as DT300 use a "standard" time-of-...
1
vote
2answers
17k views

LED light bulbs flicker when switched off - where does the energy come from?

Outside my house, at the front, I have a set-up of 3 lights attached to the wall. These lights can be switched on using a switch inside the house. Furtermore, they are attached to an infra-red sensor ...
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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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1answer
696 views

Frequency Counting on a Raspberry PI

I am trying to count a square wave on a Raspberry PI. I tried a variety of approaches: http://abyz.co.uk/rpi/pigpio/examples.html (Freq counter 1 and 2) http://www.dnacoil.com/tools/measuring-light-...
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3answers
395 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 ...
1
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1answer
347 views

What is used to detect light from fiber optic signals in high speed Internet?

I'm curious, do they use photodiodes or something? As far as I know, that would be the cheapest way to do high speed communications over fiber (fibre? I'm 'murican) but I'm not sure.
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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
875 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
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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3answers
3k views

Designing a Light/Dark Sensor for motors, using Transistor and and LDR

I am working on some project for which I need to turn off a motor whenever it's dark. I looked around and found some light/dark sensing circuits. However, most of these circuits use an LED that ...
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2answers
163 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 ...
1
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1answer
202 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 ...
1
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2answers
63 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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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 ...
1
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1answer
449 views

Is Deuterium arc lamp a AC or DC light source?

I have created a prototype photo-detector circuit to use in spectroscopy. The micro-controller code take 120 A/D readings and then returns average. I have noticed that when I use visible light (...
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2answers
74 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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3answers
473 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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2answers
545 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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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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0answers
202 views

Calculate distance between two vehicles without using GPS

I am trying to understand if there is any way to measure the distance between two vehicles, possibly moving, without the aid of GPS. I want to measure a distance of more than 50 meters but less than ...