Leds Definition and 104 Threads

Hi! I am trying to create a circuit which can individually turn on and control 12 LEDs from 4 pins, since I am trying to adapt it to a tiny microcontroller (the Attiny85, which does not have enough pins to drive the LEDs) For this, I am using a method called Charlieplexing. You can for example...

Hi! I am questioning my design choices, but I will try to push this circuit a little more until I get a microcontroller with more pins and don't use Charlieplexing. Charlieplexing is a method of controlling n*(n-1), in this case LEDs, using n GPIO pins. This is achieved by alternating the...

Hello! Forgive me for this absolute beginner question. I was trying to experiment with Charlieplexing a couple of LEDs. Charlieplexing is a technique that utilizes the fact that many microcontrollers attend a high impedance state when set to input and of course that diodes only pass current one...

@berkeman - remember the guy who asked about replacing 0603? Quite accidentally I just found something called "SMD challenge misery edition" (there are several versions, TBH I have no idea which one was first so I just grabbed the best picture I could find). Yes, the idea is to hand solder the...

Light-emitting diodes (LEDs) are replacing traditional lighting technology -- such as halogen -- in high-power lamps, as LEDs are much more efficient (Lumens/W) and longer-lasting. A commercial example of high-power LED flood lights: High Power 3000W LED Flood Light - Lsleds NOTE: The above...

I recently re-watched this video: And I wondered, how are +5000 LEDs addressed/controlled? At 600 x600 DPI and an 8.5"x11" printing area, you need ~ 5120 LEDs across and 6600 scans. At 20 ppm, the scans would need to be less than 3 seconds total ( need to allow time for fusing, etc), so ~...

Hi, I am looking for a suitable method to couple light from 2 LEDs into a fiber and then join both fibers, so that I only have one fiber at the end so that both wavelengths can be emitted from a single fiber. The first coupling step from LED into fiber seems to be more easy, I already heard...

The brightness of an LED is a result of the current passing through it. The current is a function of the voltage across the LED. The duty cycle represents the percentage of the time period that the signal is in the ON state ( which means that the voltage is at max value as compared to 0 V for...

Hi Everyone, This is my first post and I hope to work with you on this to gain a fuller understanding. I'm currently designing an LED circuit with 60 3 watt LEDs. Input power is both 120VAC for North American and 230VAC for other countries. I know this is pretty basicbut what is the best way...

My two years old son loves lights and computers. I was thinking to buy an Arduino or a Raspberry pi like single board to control a LED matrix panel. What I want is to be able to control individual LEDs by pressing on keys on a keyboard. Example: by pressing "a", a LED lights up, "b" another LED...

I would like to turn on and off 100 external (non screen) LEDs through my PC. I was thinking to assign each pin on my serial port an LED, because apparently you can control the power on serial port pins if I understand correctly. The problem is that even if I do control each pin on a port, what...

I've read that using a pinhole aperture and a wavelength filter can turn a "white" incoherent light source like a light bulb into a temporally and spatially coherent light source (albeit at low efficiency). Can a temporally and spatially coherent light source be made with a monoenergetic (or...

I'm working on a small crank-able light using a DC motor,capacitors, and LEDs with a joule thief to drain the capacitors completely when the voltage in them drops too low for the LEDs. However I want the power from the capacitors to be able to go directly to the LEDs before the capacitors drop...

Yet again, I am getting furious about the reliability of domestic LEDs. I have been moved to ask for the current views and experience of PF about them. The top of my search list on PF has an old 2012 post of mine, moaning about the same thing. There are some interesting comments from PF on that...

Hello all. Thanks for taking up your time to read my post. I checked the currents that passed through several LEDs for MIC2287CBD5 as the datasheet of http://www.kynix.com/uploadfiles/pdf2286/MIC2287CBD5.pdf at a particular voltage. They varied from 12.0 to 15.1 mA at 3.0 V. I then connected...

Attached is a picture of my set-up. It is very simple and if for a car (12V) The LED kit comes with 3 options: Hard wire install, cigarette lighter install, and 9 + 9 V battery demo. The peculiar thing is when I connect the hard wire install plug (shown at the top of the picture) to a...

Saw an old thread, "Led Lights Burn With Power Off" and it was closed... so let me check out an issue with you all: in this same situation and I don't want the lights softly glowing, could I put a 100 ohm 1/4 watt resister in line to block the teeny tiny induced current? Would it behave well...

Hi all, a bit of a hypothetical for you. If I wish to drive a 3V LED at 20 mA from a 12V battery, I can use a dropper resistor. I subtract the LED's forward voltage from the 12V to get 9V, and divide this by the 20 mA, to get the value of resistor needed. R=V/I = 9/0.02 = 450 ohm. However...

Hi. Has anyone already done the work to back out the standard luminosity function so I can go from lumens at a particular wavelength to radiant flux in Watts? I have visible LED spec sheets with optical characteristics in lumens and I want to calculate the outputs in W. My NIR LED has specs in...

I am playing with Arduino and LEDs at the moment. LED needs a resistor to limit current, that's clear. However, all examples I see use separate resistor for each diode. As far as I can tell electrically (in terms of limiting current) it shouldn't matter much whether we use single resistor for...

Referring to LEDs as I'm not aware of any other "colour-producing" light, does blue light use more energy than red light? Planck's formula (E=hf) leads me to believe that blue light would drain a battery quicker than red, due to its higher frequency. Surely a device emitting blue light would...

Back story : I have cheap 12v LED 5050 strip from China. Question: how do LEDs respond to 13v and 14v in terms of % intensity with higher voltage neglecting lifespan and assuming proper heat dissipation. Details: the LEDs at 60/m rated 14.6w at 12v. They are typically 3led in series with a...

Hello forums, in the context of a little DIY-project I am planning to build a rudimentary fluorometer, which is actually doing nothing but checking whether an amount of protein is fluorescing or not, and roughly measuring its intensity. A highpower LED is used to excite the protein to the...

I am desgning a circuit(network), where i need to show the path traversed by the greater part of the current at each node, consecutively. using an ammeter (or voltmeter) in every branch (around 20) makes it too tedious. Will LEDs do the required work? But they would light up at all locations...

I have a small motorcycle and have changed the incandescent bulbs to LED. It seems the bulbs were powered by AC off the magneto generator and AC thru the rectifier powered the 6 volt battery. Is it ok to run LED this way or should I add diodes like in option a or b of diagram?

Hi folks, I would like to clarify few doubts on my mini-project as mentioned below: I am designing a small kit using a transistor (2N3904) and an OP-AMP (LM741- Voltage follower) with few resistors connected to them. My power supply voltage value is 5V. Please refer to the below picture for...

How many led's 20ma at 3 volt can one run from a fixed supply voltage of 110 volt dc and a maximum supply of 20ma? I come up with 36.

I'm trying to wrap my head around thermal management of LEDs and LED driver circuits. http://blogs.indium.com/blog/amanda-hartnett/controlling-junction-temperature-of-leds-with-thermal-management-materials A concern has been expressed that a lighting supplier needs to demonstrate (not sure...

I'm making an array of 11 3.3V LEDs, and I've got multiple various setups possible depending on source voltage (batteries supplying either 6V, 9V, or 12V) and whether I decide to put a bunch of the LEDs in a combination of series/parallel or all in parallel. I need to maximize battery life, so...

Specifically what does the color temperature on light bulbs it indicate? because, it clearly does not indicate the wavelength of max intensity.

Here are some of my thoughts: - thermal management of individual LEDs in a RBG system - photon absorption in phosphor coating - exponential decay in intensity - CCT/ CRT?

I want to make a solar simulator with LEDs. I want to get a net intensity of 1 Sun(1000 W/m^2). My LEDs have the following specifications: LUXEON S LXS8-PW30 Luminous flux at 700 mA, 85°C* 1315 lm Radiant flux at 700 mA, 85°C 4113 mW 1931 CIE color points at 700 mA, 85°C (0.4304, 0.4030)...

The electrons need energy to cross the potential barrier between the N and P types. So apply a voltage and they get over and recombine with the "holes" and emit a certain wavelength of light. Then what happens? Does the voltage have to be great enough to then knock them out of the holes and send...

Homework Statement The asker needs to know the angles to mount three LEDs inside a traditional mains powered light bulb shaped enclosure "to get even radiation from the LEDs", and also the position of the covering plastic sphere in relation to the LEDs. (I was thinking that the position of the...

Hi! I had an interesting chat with a physisist colleague of mine this week. Working with modern small electronic components I began to wonder why my extremely pointy probes, measureing the direction of the light emission diode, stuck so irritating hard to it that it could not break loose after...

i'm shopping online for an LED bulb and one site gives the estimated lifetime of the LED. So, i was wondering what exactly is happening to make the device "old" and no longer work?

Hi All, The other day I ordered LED's from digikey to do some electrical experiments for fun, and to my surprise I got these: http://www.digikey.com/product-detail/en/SMLP12WBC7W1/511-1616-2-ND/1801991 They are literally too small to even hold. They are like the size of knat. What do I do...

I am detecting detonation in a SI engine using a knock sensor (pizeo element). What I would really like is to have 3 leds that light up as the knock gets more severe. I have the knock sensor running into an op amp powered by a 9v battery. I am listening to the output with a pair of head...

I have a pressure sensor that gives off 4 volts when actuated and I would like to transmit it a distance to an LED light. So I found these RF Link Transmitter/Receiver at 434MHz: https://www.sparkfun.com/products/10534 https://www.sparkfun.com/products/10532 The data sheets and...

Hi guys, I have to calculate de optical power output of a set of LEDs. For that I used a photodiode to measure the photocurrent at each wavelength and then calculate the optical power at each wavelength using the following formula: R (A/W) = I/P, where R is the responsivity of the...

Hi, electrical engineering has always interested me and recently I have been trying to trying pick it up as a hobby by doing simple soldering exercises. While everything has gone smooth so far, I have hit a snag with the current little project I have been working on. So my goal is to light 2...

I bought some 'super bright' LEDs from sparkfun: https://www.sparkfun.com/products/8861 I got the green one, the red one, and the blue one. Guys in the comments are saying, "Wow these things light up a whole room at 75mA!" So I bought them to make a night light. I checked out the...

Hi guys. I'm an architecture student who is designing a lamp that will be made up of multiple, modular pieces of plywood. Each piece will be a hexagon containing 6 LED lights (one on each side). The idea is to have a base that plugs into a socket with a wall wart: I was thinking 12 volts AC...

Hello everyone, I am currently a sophomore in computer engineering, so I don't quite know enough to figure this out on my own, so I was hoping you guys could help me. I really like the idea of a color organ to visualize music...

Hi all, I am trying to build a circuit for driving multiple LEDs under test at a given current, and the LEDs are to be individually tested with multimeter. Now I know I could just run them all in series and they would get the same current, but if one LED breaks, then the whole circuit goes...

Ok so I've been trying to power a few small lights in my shed and I've read on a few sites about PoE (power over ethernet). i just wondered or has anyone had experience with it? what kind of current/voltage is the cable capable of etc I am guessing its not just as simple of wiring 2 of the 8...

Homework Statement We can't use anything else, and just have to make a logic circuit (either OR, AND or NOT) with just this material. We can use less or more diodes but I have only 5. Homework Equations The Attempt at a Solution I tried setting it up like doides but no help at...

I recently purchased two strings of RGB LED lights, the kind you can set to all sorts of colors by combining red, green and blue in various amounts. Unfortunately, I strongly suspect that the blue and green led-pieces produce light that is contaminated with UV. Various UV-reactive things in...

In a COB product with FR-4 substrate, blue light chip excites yellow phosphor to form white light. Why is room temperature aging attenuation higher than 85 degree/85% RH aging attenuation? (After 1000h lighting, Attr=7% while Att85=1%) (If you have further questions about how I do the...

I’m trying to install some LEDs in my footwells. I have a pink wire, which is my positive, and a gray wire, which is my negavtive. This is a negative switched circuit. So, is it ok to hook it up like this? 1 Positive of LEDs to pink, negative to gray. 2 Then, use a diode on the gray...