Questions tagged [light]
Light is a tag about anything generates photons in the visible spectrum
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Why my brake lights have two grounds? [closed]
I have an e-bike brake light that runs off a 48 V battery.
The LED light has three wires, red (+), black (-) and yellow (-).
I connected the red and and black wires to the (+) and (-) terminals of the ...
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NE555 + CD4017 Airplane Strobe Light with LDR
Engineers! I have built a simple airplane strobe light using NE555 and CD4017 in order to flash two LED in a different pattern. I have added an LDR resistor with a transistor in order to switch OFF ...
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Adding PPF/PPFD / Scaling
When considering PPF or PPFD, can you multiply the PPF of the light source by a factor (for example x100) and divide the calculated PPFD value by it to obtain the same results? In another way - is PPF ...
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Can someone help me to identify this 6-pin SMD IC?
Is anyone able to help me identify this 6-pin SMD IC, or know what it does? I've been googling for it but I'm unable to find it or figure out what it is from the markings on it.
As seen in the ...
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What is this white component in this emergency light?
I have an emergency light, which I opened up. I see there is a yellow cable going to that sot of electronic component (by 'L+'). Is this a light sensor?
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Replacing three-wire timed switch with a microcontroller
The building is surrounded by 6 lights and 4 buttons, 3 of which are illuminated.
Right now the circuit is managed by a Perry 1IT 1051. Here are the official schematics:
While I'm happy with the ...
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Making a flashlight watch
My son has a rare genetic disorder (nyctalopia) in which the rods in his eyes don't work and so he can't see anything in dim light. I've seen him very confused and scared in environments where I can ...
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What are LCD subpixels made of?
Just curious. I don't really need to know this level of granular detail for my job (AV technician) but in courses/articles about color LCD displays they explain everything... except what the red, ...
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Conversion of portable fluorescent to UV-C lamp
I am modifying an off-the-shelf portable fluorescent light to a UV-C light for use in field illumination. I found a 13W UV-C 4-pin bulb that is the same physically as the OEM fluorescent, so thought I ...
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OPT3001 - Read before Conversion in complete
What will happen if Light Sensor - OPT3001 conversion time field is set to 800ms but read request is set every 100ms. Unable to find/locate the info in Datasheet.
Additions Info:
Transparent hystersis ...
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RGB LED Selection and Perceived Brightness
I'm trying to design a smart light with 800-1000 lm white LED strings (warm+cool) and RGB, but I'm having a hard time comparing the luminous intensity or sometimes mcd ratings.
How can I select red, ...
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What is this light sensor part?
This light sensor off of my lincoln town car stopped working. It is supposed to turn on/off my headlights when it is bright enough outside. I don't know what this part would be and would love some ...
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How to add delay to circuit
I have this circuit where a switch is used to toggle between the blue and red LED.
How can I add a delay so that when an ON switch is tuned OFF the RED LED doesn't turn on immediately
If the switch ...
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LED limit to short pulse and high power
I’m studying the viability of a small footprint distance detector that relies on a LED, a photodetector and some lenses. It’s meant for a distance above 150m, where the light beam travel time is ...
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What are the little bits of metal that come out of light bulb filaments and why do they stick to only one terminal?
Recently I changed the headlights in my car and took a few micrographs of the filaments. A couple composite photos of old bulbs:
For reference, here's a new bulb filament:
On the left wire in the ...
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How does one dim very high LED loads with PWM?
Suppose we take a LED source that can be dimmed using PWM (i.e., by turning power on and off at high frequency). Dimmers exist for these sources up to, say, 5A at 24V. But what if I want to dim 10x ...
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Why don't these LED's work in parallel?
noobie here as will be obvious in the next few sentences :)
I have this strip of LED's Amazon LEDs. I thought/hoped that since each led has its own resistor that this would mean i could cut off ...
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IR LED Safety: Where does this OSRAM App note (AN090) formula come from?
The formula is from OSRAM application note AN090 "Eye safety of IREDs used in lamp applications":
$$ L_{ir} \approx \frac{I_e R(\lambda)}{Z^2} $$
In the app note, they don't give a reference ...
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What is the reason for some flashlights emitting light in a square shape?
Here's an image of a flashlight that produces light in a "square" shape:
What is the purpose of this square light pattern, and why was it designed as a square as opposed to the traditional ...
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How to replace TCRT5000 IR sensor with TCRT1000 IR sensor
I've got a pulse sensing circuit based on the TCRT5000 IR sensor. Its working fine and I can easily see the pulse when finger is placed. But I tried replacing it with the TCRT1000 but there is ...
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Which of these wires is positive and which is negative?
I know that in DC circuits the colour code is often (but not always) that red is positive and black is negative.
On this AC mains wiring the wires are blue and brown. Does anyone know which is which? ...
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What is the name of this connector and where can I find it?
Any ideas on where I can locate this connector? It is from a bike light and connected directly to 18650 battery. 3mm x 2mm with 4 holes, but 2 wires from the battery. On the motherboard the connector ...
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Christmas lights glow for hours despite being unplugged
I have a set of Christmas lights (the LEDs are red, green, blue and yellow) that I unplugged last night, and in the morning the bulbs continued to glow dimly but noticeably.
It seems like it's been ...
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Dry film PCB yellow light
I print out a negative on acetate paper, I stick it on a copper plate with dry film, and I press it with an iron. While doing these operations, we have to be in yellow light, what is the content of ...
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What powers an LED across an open switch?
Honestly, I just can’t seem to figure out how this switch works.
I have a light switch that incorporates an LED that is on when the light is off. The neutral is not connected to the switch. The switch ...
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Minimum light bulb wattage for solar simulator
I am trying to design a simple homemade solar simulator. I have picked metal-halide lamps as my light source.
To achieve an irradiance of 1000 W/m2, I don't know what wattage of light bulbs are needed....
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Light bulb as limit, to what is current limited to?
I was wondering, if I use a light bulb as a current limiter when working with some electronic device, in case of a short circuit - what determines the current that is allowed to pass to the electronic ...
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Powering 12 LED tea lights with recycled power adapter?
I have 12 tea lights that are each powered by a C2030 3 V battery.
Like many of us I have a box of various chargers and whatnot.
Is this as simple as finding one outputting 3 V and splitting it 12 ...
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Will 500 THz frequency glow antenna while radiating?
I read 700 nm wavelength is visible light, for which frequency is 429 THz. If we produce that frequency, whether antenna will be radiating visible light?
Correct me if wrong.
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How to select the proper LEDs for light fixture
This light fixture has 3 heads with 15 LEDs for each head. The 3 heads are connected in series. In each head, there are 3 sets of 5 LEDs connected in parallel. The 3 LED sets of 5 for each head are ...
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Can usb power a 40W led light? [closed]
I've recently came across some usb led grow lights that are rated up to 40W. My question is how does a regular usb 2.0 or even 3.0 be able to power it? Is it a scam?
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Light reading diode?
I’m trying to think of a device to measure amount of UVA & UVB daylight for plants in my shed and so trying to work out what I could use to measure:
The amount of light
Its type
Its time
Be able ...
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How to make LEDs produce light like incandescent light? [closed]
LED light flickers around 100 Hz and is caused by rectifying AC power. How can LEDs be made to emit constant light that comes from an incandescent element which does not flicker?
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Open circuit photodiode energy
Where does a photo-diode use the energy it collects from light and other EM waves when not loaded? Does it dissipate it as heat, reflect it or something else?
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LED light transmission through prepreg in a PCB
I've designed a LED board 8x8 where LEDs are assembled in reverse. So, there is a through hole at every LED position, LEDs assembled at the bottom, and light goes through the PCB hole and comes out ...
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Looking for a simple circuit to switch power to IR LED's at night (2A @ 12 volts)
I'm looking for a simple and cheap way to switch power to a few hi-current IR led's at night. So some sort of photo detector and a solid-state or traditional relay. Unless there's a single-component ...
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What is this solar path light component?
Just for fun and curiosity, I decided to reverse engineer an old, cheap solar path light. It's a fairly simple circuit, but there's a component I can't find any information on. It has transistor-style ...
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Mixing light from multiple leds
I'm trying to design a device that produces visible light with a somewhat controllable spectrum. My goal is to measure the human eye cone cell responses by switching between two different spectra and ...
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How do seven segment displays show black numbers?
Usually, seven-segment displays emit red coloured light, which is understandable. But in digital watches, the common colour used for the numbers displayed is black.
But black light itself can't be ...
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IR LED Safety: Subtend Angle and Retinal Exposure Limit
The relevant formulas from OSRAM AN090 "Eye safety of IREDs used in lamp applications" with slight modifications :
$$ Z = (l + w)/2 $$
$$ \alpha = Z/d $$
$$ L_{ir} \approx \frac{I_e R(\...
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How to change the wavelength of LEDs in Proteus?
I have a problem in designing a circuit for my project.
Can anyone explain how to simulate an LED with 940, 1550, and 1650 nm in Proteus software?
Dors the emission coefficient of LEDs in Proteus help ...
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How to calculate the total power of a LED using solid angle?
I have a LED with the max power of 130mW/sr and an opening angle of +-10° (so approx. around 20°). I conducted an experiment using this LED, the LED shines light to an un-doped silicon semiconductor ...
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Why are metal halide bulbs always ~130V?
I noticed that - even though the local voltage is 240V - metal halide bulbs are always sold as 130V bulbs, and their product sheets list the maximum voltage as 130V. Do perhaps all flood lights that ...
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Incandescent light bulb in proteus
How to create a simulation model of The incandescent light bulb in Proteus?
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What is this through-hole component holder used on aluminum PCBs?
I've been buying these cheaps LED lightbulbs and tore them down to see how the LEDs are driven.
On all of them I have found this surface mount component that allows a through hole component (here a ...
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Creating ZigBee RGB Compatible Light - Raspberry Pi
I currently have a Rasberry Pi hooked up to a 64x32 LED matrix. It runs some custom Python scripts to control the colour and display of the matrix, which works great and lets me adjust the settings ...
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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 ...
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Is it possible to control the frequency of light?
I mean, controlling directly in the source, not filtering the light or arranging density of the medium. For example, brightness can be controlled by current or voltage directly. However, when I came ...
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Photo Diode Receiver
I have designed a 5KHz Photo Diode Receiver circuit that Consists of a number of blocks. first stage of this circuit is a TIA.
I have problem with DC IR Light (Like SUN Light), when sun light shine on ...
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Why did this fog lamp turn on with either configuration of power/ground? [closed]
My friend and I were replacing a burnt out fog lamp on his car. When it was time to make the connection, I wanted to make sure which wire was power and ground, so we don’t cause a short to the new ...
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