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Questions tagged [light]

Light is a tag about anything generates photons in the visible spectrum

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Is it dangerous to have no cover on a fluorescent tube (bathroom light)? [closed]

Is it dangerous to have no cover on a fluorescent tube (bathroom light)? I have a bathroom light above my sink with two fluorescent tubes. The acrylic cover sheet that slots into the fixture is "...
Jocelyn Yeoman's user avatar
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0 answers
22 views

A scheme to control a number of ceiling light bulbs being on with a single switch [migrated]

I have a ceiling light with two bulbs and only two wires (live and neithral) arriving to it (220-250v AC) and a SPST switch. I want to connect one bulb directly to those wires and I want the other ...
Hug you Nvidia's user avatar
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1 answer
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Can a photon be modeled using AC driven electron and AC driven wire loop?

Can a photon ("electromagnetic wave packet") be simulated in software as an electron bouncing up and down (for the oscillating E field) and a loop of electrons with neutralized electrostatic ...
user323947's user avatar
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62 views

Automatic on and off light strip [duplicate]

I am trying to make an led strip turn on and off automatically based on sunlight. So when it is dark the lights will be on full brightness and when it is daytime the lights would be off. The led strip ...
Fatema Ali's user avatar
1 vote
1 answer
61 views

Can someone help me with a LED light fixture puzzlement? [closed]

I have been buying and using LED bulbs from the Dollar Tree for many years. I have never had an issue with them in the past. Just the occasional burn out in my home office fixture because it stays on ...
russT's user avatar
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2 votes
3 answers
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What is the name of these old colored indicator bulbs and are they still manufactured?

As an electronics project, I would like to create a PCB that generates random blinking lights similar to the computer panel props featured in late 60s/70s era television series: The scale is possibly ...
Noel Whitemore's user avatar
1 vote
2 answers
102 views

Designing a DIY low level light therapy device (LLLT)

I am designing a low level light therapy (LLLT) device similar to the one in this video. Mine will be smaller using twenty each (for a total of 40) of two kinds of 3W LEDs: 2.4V 0.6A -- 660Nm red 1....
Bravo Foxtrot's user avatar
1 vote
0 answers
93 views

Can I use a handheld spectrophotometer to calibrate my TCS3200-based fluid color assessment system?

I'm trying to build a system that measures color and turbidity within the tube that exits a patient's brain. Using a TCS3200 sensor and an Arduino micro, and a custom-made housing to ensure a dark ...
Bilal Bahadır Akbulut's user avatar
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1 answer
61 views

What component is missing?

I have an address sign that is supposed to light when it gets dark outside. The issue is the photodiode (assume that's what the part is) is broken and has broken off the board. I have tried connecting ...
Kasriel Lewis's user avatar
1 vote
1 answer
65 views

How supply an outdoor string light with 10 LED bulbs 0.8W?

I currently have a outdoor string light with 10 LED bulbs 0.8W powered by a 3.7V lithium battery and recharged by a solar panel (5.5V 295mA). Over time the battery discharges and no longer works. I've ...
Thom's user avatar
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2 votes
1 answer
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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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1 vote
2 answers
139 views

Dimming light idea

I have this idea to dim a light. The problem is that my EBS simulation software won't allow me to see the actual result of the dimming. The only way to test it out is to physically construct the ...
Zipho Lunika's user avatar
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1 answer
34 views

Error Indicator Light on Heater

I have a heater with a neon bulb wired in parallel with a safety cutoff switch. The full current of the heater goes through the safety switch. If the switch trips, wouldn’t the full current just go ...
Mike Lauritsen's user avatar
1 vote
4 answers
96 views

Usability of COB LED filaments as replacement for traditional filaments

COB LED filament household lightbulbs are a thing now. Can someone explain to me what limitations there are to using these COB filaments in car headlights? They emit a very similar light pattern if ...
Dan's user avatar
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2 answers
160 views

How open this Christmas light plug to change fuse? [closed]

I'm trying to get to the fuse in this plug (pictured below) and it looks like I'm going to break it instead. All the videos and instructions I've found show a different plug that it is very easy to ...
Rodo's user avatar
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2 votes
3 answers
691 views

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 ...
Svet GEoff's user avatar
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1 answer
17 views

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 ...
Ocean's user avatar
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1 vote
0 answers
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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 ...
MiRo's user avatar
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0 votes
0 answers
116 views

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?
JoeyB's user avatar
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0 votes
1 answer
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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 ...
Davide Beatrici's user avatar
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0 answers
56 views

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 ...
Wapiti's user avatar
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1 answer
72 views

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, ...
itsagift's user avatar
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0 answers
44 views

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 ...
MrTim's user avatar
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0 votes
2 answers
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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 ...
Joses Paul's user avatar
1 vote
2 answers
107 views

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, ...
Dan's user avatar
  • 133
1 vote
1 answer
144 views

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 ...
2ndpower's user avatar
0 votes
1 answer
210 views

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 ...
Bach's user avatar
  • 115
3 votes
2 answers
197 views

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 ...
PDuarte's user avatar
  • 1,399
52 votes
4 answers
4k views

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 ...
rsaxvc's user avatar
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0 votes
3 answers
203 views

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 ...
Dmitri Nesteruk's user avatar
1 vote
1 answer
101 views

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 ...
Joe1250's user avatar
  • 11
2 votes
0 answers
118 views

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 ...
InTheWorks's user avatar
5 votes
2 answers
3k views

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 ...
grandsirr's user avatar
  • 175
3 votes
1 answer
170 views

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 ...
DribbleNibble's user avatar
0 votes
3 answers
2k views

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? ...
Mito's user avatar
  • 411
1 vote
1 answer
146 views

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 ...
dmas72's user avatar
  • 11
1 vote
4 answers
634 views

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 ...
Dyl2013's user avatar
  • 51
0 votes
1 answer
74 views

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 ...
Mehmet Emin ARSLAN's user avatar
0 votes
1 answer
169 views

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 ...
Coconut's user avatar
  • 87
0 votes
1 answer
144 views

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....
flamezdude's user avatar
6 votes
4 answers
3k views

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 ...
komrad2236's user avatar
1 vote
1 answer
66 views

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 ...
John Bell's user avatar
1 vote
0 answers
133 views

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.
E2.0's user avatar
  • 23
2 votes
1 answer
164 views

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 ...
ednja's user avatar
  • 31
0 votes
1 answer
138 views

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?
unknowncat's user avatar
3 votes
1 answer
132 views

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 ...
grassfingers's user avatar
-3 votes
1 answer
132 views

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?
Justintimeforfun's user avatar
0 votes
3 answers
133 views

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?
td211's user avatar
  • 107
4 votes
1 answer
235 views

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 ...
user avatar
1 vote
1 answer
37 views

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 ...
Peggy Schafer's user avatar

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