Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

1
vote
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
votes
1answer
157 views

BH1750 Sensor ICs - Block Diagram - Why it has capacitor connect output to input of OpAmp?

The image from BH1750FVI datasheet. http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1750fvi-e.pdf (page 4) I don't know why it has the capacitor connect output and input of ...
20
votes
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 ...
1
vote
1answer
346 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.
2
votes
1answer
968 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-...
18
votes
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! ...
2
votes
4answers
552 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 ...
4
votes
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 ...
-1
votes
3answers
445 views

Ideas required to detect object position

I am trying to figure out the possible solutions for detecting the position of the object in the container. the below image is to describe the scenario. Object: spherical diameter: 5 - 7mm Type: ...
0
votes
3answers
4k views

What are the limitations of using a LDR sensor?

I have to explain limitations for a photoresistor/LDR . I've read the book, and searched online but find nothing. Can I get help with this ? Are things that the sensor can NOT do, which other tools ...
0
votes
1answer
51 views

What material should be used for large-scale electron emission?

Photocathodes, to my knowledge, are usually used for precise and fast light-detection. But would they also be suited for the sole objective of ionizing the surrounding air? If no, what materials would ...
-3
votes
1answer
117 views

How do I build a Circut to create temperature changes in LEDs? Looking for a range of 3000 to 6,000 for photography? [closed]

I see commercial lights for photography that can change color in the range of 3-6,000 or tungsten to daylight values. These are not arrays of three RGB lights but rather single LEDs and the ...
0
votes
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 ...
0
votes
1answer
287 views

Laser detector parts

I have been trying to find laser level detector components. I took apart one on hand, see what looks like basic photodiodes and a light tube. Note the 3 photodiodes visible in the center part. ...
0
votes
1answer
923 views

I need help with a simple IR circuit to control electromagnets

I have a project , I know what I want it to do but don’t know how or the components needed. I want this IR beam-break trigger to control two of these 12v magnets (.33A each). When the beam is broken, ...
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 ...
0
votes
2answers
738 views

Sensing directional light

I am looking to detect the amount of light coming from a specific direction that lands in a specific area on a PCB. In my research, I have only found ambient light sensors and never any kind of ...
4
votes
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?
0
votes
1answer
405 views

Light Detector/Identifier circuit using photodiodes

I'm currently completing my final year project and am currently stuck going round in circles as how to complete it. To summarise: I need to design a circuit which is capable of IDENTIFYING a light ...
0
votes
1answer
91 views

Help Interpreting “Max light exposure” rating for TSL1406R

I've purchased a TSL1406 Linear Sensor Array to read the position of a laser dot. The "Absolute Maximum Ratings" section in the datasheet specifies "Maximum light exposure at 638nm" as 5 mJ/cm^2. ...
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 ...
0
votes
2answers
81 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 ...
0
votes
2answers
333 views

PIR sensor based LED light controller

I have a PIR sensor module based on BIS00001 IC. I am using the 3.3 VDC output signal of the sensor module to trigger an LED matrix using a low side NPN transistor and a current limiting resistor. ...
2
votes
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
votes
1answer
561 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
votes
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 ...
4
votes
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 ...
1
vote
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 ...
0
votes
1answer
101 views

photodiode, ldr and light source

I need to measure the red or green or blue component of a light source. Are there any resistor or diode with this specific capability? I found some diode with rgb filter, but i'd want to know if there ...
0
votes
1answer
136 views

Do flat distance lasers exist?

In short, I want to create a flat laser plane that knows where it's being penetrated. If flat distance lasers do not exist, what other options do? I considered using several regular distance lasers ...
0
votes
2answers
1k views

How to stop a motor when car approaches wall - phototransistor?

In a school competition for my son, he wants to make a toy car that will stop before it hits a wall (before, not making an impact). It can go as slow as it likes and cannot be remote controlled. I ...
0
votes
2answers
68 views

Detecting object Water Reservoir

You have this large water reservoir, for example, a bathtub. How can you detect when an object is thrown (rock, etc) into a big water reservoir? Vibrating sensor, ultrasonic etc?
1
vote
1answer
447 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 (...
1
vote
1answer
692 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-...
0
votes
1answer
490 views

Why would any smartphone need an ambient light sensor if it already has a front-facing camera?

Why would any smartphone (e.g. the Samsung Galaxy S5) need an ambient light sensor if it already has a front-facing camera? Surely it requires time and money for the engineers to design an ambient ...
2
votes
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 ...
0
votes
1answer
2k views

TSL2591 sensor value calculation

I bought an TSL2591 breakout board and wanted to write driver for my board. After looking at the documentation, i found that i cannot calculate the illuminance value (in Lux) as their was algorithm ...
2
votes
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 ...
3
votes
2answers
827 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
votes
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 ...
5
votes
2answers
546 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 \...
0
votes
1answer
935 views

Laser activated switch using a photo-transistor

I would like to make a laser activated switch using a photo-transistor or an LDR, by which I can switch off the lights in a room from a long distance. I just have to point the laser and it will detect ...
18
votes
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. ...
2
votes
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
votes
2answers
572 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?...
2
votes
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. ...
3
votes
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 ...
4
votes
2answers
806 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'...