What Do I Need to Know to Design an LED Lamp

First, using a resistor to drop from 120V to 3V is very, VERY inefficient. You will be burning off about 90% of your energy in heat. You need a transformer here, at the very least.

Just doing the math: If you need 3A/3.3V for light, then 3A/120V is 360 Watts of power, of which you're extracting 9.9W for the actual diodes, and thus burn about 350W in heat in the resistors.Second, LEDs in parallel is unreliable, because the actual voltage drop of the LEDs will vary a little bit because of process variance, and thus some of the LEDs will draw a lot more current than others. This will result in the lower-voltage LEDs burning out, and the higher-voltage LEDs being dim. To fix this, you need one current limiting resistor per LED, rather than a single one for the gang.Finally, what's the point of wiring half of them each way? Why not use a bridge rectifier?

So I had an idea for an LED lamp. I've got some old flashlights that have older model CREE LEDs.

My idea is that I'd put the LEDs in parallel, alternating polarity so that for each phase of AC, half of the LEDs will be conducting.

The array of LEDs would be in series with a resistor and a fuse to drop voltage from 110 VRMS from the outlet to 3VRMS over the LEDs and prevent the LEDs from breaking if something catastrophic happens (and to compensate for my own failings.)

The LEDs have a 5V reverse voltage and a 3.3V forward voltage at 3A at 80 deg C, so I figure if I limit to 3 VRMS I should't hit the reverse voltage and make badness happen.

With this in mind ... I am only passingly familiar with anything more advanced than kirchov's and ohm's laws. I can't apply ohm's law to the diodes, so what do I need to know to figure out the resistor value for n parallel diode pairs (Or maybe n sets of 5 in series and put those in parallel)? or is it just a bad idea?

·OTHER ANSWER:

So I had an idea for an LED lamp. I've got some old flashlights that have older model CREE LEDs.

My idea is that I'd put the LEDs in parallel, alternating polarity so that for each phase of AC, half of the LEDs will be conducting.

The array of LEDs would be in series with a resistor and a fuse to drop voltage from 110 VRMS from the outlet to 3VRMS over the LEDs and prevent the LEDs from breaking if something catastrophic happens (and to compensate for my own failings.)

The LEDs have a 5V reverse voltage and a 3.3V forward voltage at 3A at 80 deg C, so I figure if I limit to 3 VRMS I should't hit the reverse voltage and make badness happen.

With this in mind ... I am only passingly familiar with anything more advanced than kirchov's and ohm's laws. I can't apply ohm's law to the diodes, so what do I need to know to figure out the resistor value for n parallel diode pairs (Or maybe n sets of 5 in series and put those in parallel)? or is it just a bad idea?

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How to Judge the Watts of LED Lamp Beads? Differences Between LED Beads and Patches
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Abstract: LED beads have the advantages of small volume, low power consumption and long service life. They are widely used in the decoration of lamps and lanterns in our life. This paper mainly introduces how to judge the watts of LED beads? The difference between LED beads and patches.Characteristics of LED beads1. Voltage: the LED bulb uses a low-voltage power supply, and the power supply voltage is between 2-4v, which varies according to different products, so it is driven by a higher voltage power supply; Safer power supply, especially suitable for public places;2. Current: the working current is 0-15ma, and the brightness becomes bright with the increase of current3. Efficiency: the energy consumption is 80% less than that of incandescent lamps with the same light efficiency.4. Applicability: it is very small. Each unit led chip is a 3-5mm square, so it can be prepared into devices of various shapes and is suitable for changeable environment.6. Response time: the response time of incandescent lamp is millisecond and that of LED lamp is nanosecond.7. Environmental pollution: no harmful metal mercury.8. Color: changing the current can change color. The LED can easily adjust the energy band structure and band gap of the material through chemical modification to realize multi-color luminescence of red, yellow, green, blue and orange. For example, the red LED at low current can turn orange, yellow and finally green with the increase of current.Classification of LED beads1. In line low-power specifications include: straw hat / helmet, round head, concave, oval, square (2 * 3 * 4) bullet head, flat head, (3 / 5 / flat head / bread type) piranha, etc.2. SMD patches are generally divided into (3020 / 3528 / 5050, which are front emitting) / 1016 / 1024, which are side emitting light sources.3. High power LEDs can not be classified into chip series. Their power and current use are different, and their photoelectric parameters are very different. If a single high-power LED light source is not equipped with a heat dissipation base (generally hexagonal aluminum base), its appearance is not much different from that of ordinary patches. The high-power LED light source is circular, and the packaging method is basically the same as that of SMD patches, but it is essentially different from SMD patches in service conditions / environment / effect.Differences between LED beads and led patchesThe LED bulb and the core inside the LED patch are the same. The angle of the bulb can be very small (the light is relatively concentrated and far, but the irradiation range is limited). The general angle of the patch is relatively large. Supplement: the lamp bead has high power and the patch has low power.1. The power of LED beads is different. High power LED lamps generally use 1W high-power LED beads, 1-3W coexistence high-power LED beads and cob high-power. The maximum power of a single LED of high-power lamp bead can be more than 200W. Low power LED lamps generally use SMD lamp beads, mainly including 5050 lamp beads, each 0.2W, 3528 lamp beads, each 0.06w, 3014 lamp beads, each 0.1W, 5630 lamp beads, each 0.5W, 5730 lamp beads, each 0.5W.2. Different costs from the perspective of product cost, the cost of high-power LED beads is higher than that of small power. First, the cost of high-power LED itself is higher. Second, high-power LED should be added with aluminum heat sink, and low-power can meet the requirements as long as ordinary circuit board and natural heat dissipation are used.3. Different LED lamps are used. High power LED is basically used in products with high requirements for light source per unit area, such as LED ceiling lamp, LED projection lamp, LED bulb lamp, street lamp, etc. Low power LED is basically used in products with less patch area, poor heat dissipation and low requirements for light emission per unit area, such as LED ceiling lamp, LED fluorescent lamp, LED panel lamp, LED lamp strip, etc.How to judge the watts of LED lamp beads?Low power (such as 5mm straw hat, 5mm condenser, 3528 package, etc.), about 0.06w.Medium power (such as 8mm straw hat, 10mm straw hat, 5050 encapsulated, etc.) 0.2w-0.5w.High power includes 1W, 3W, 5W, 10W... 100W.Articles related to LED lamp beads:What are the classifications of LED beads? What are the types of LED beadsDetailed description of LED lamp bead parameters and selection skills of LED lamp beadsLed bead model brightness ranking_ How to fix the LED light when it doesn't workDetailed explanation of calculation method of LED bulb resistance
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Dimming USB Led Lamp
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That's why strobes are more often preferred for still photography, and hot lights are more often used for video (where strobes aren't an option).------I need help fixing a chest freezerNo the led is not your problem!An led will only show if there is voltage. Try putting a load on that outlet a volt meter may show good but plug in a curling iron and nothing. This happens with backstabbed receptacles all the time , sometimes a loose screw or wirenut . Try a load test and you may find the power goes way.------Technique to measure/infer Vf for LED given IfAssuming an LED or string of LEDs with no current limiting built in:The simplest way is to connect a constant current supply which is set to 700mA and can provide at least 14V, preferably more. Note, that's a constant current not a current limited supply.Then measure the voltage across the LED. That will be the forward voltage------Using US lamps in Europe closedThere are several different kinds of circuits used for LED lamps. There are also different kinds of "adapters". Many combinations of lamps and adapters are NOT compatible. You must do more careful and detailed analysis of how each different lamp is constructed and what kind of converter or adapter is suitable.Your question is over-simplified and cannot be properly answered as a generic generalization------How can this lighting/color effect be done?I don't see how it can be done in camera unless you set up a bunch of monochromatic objects in a studio. Sure it can be done but may be more difficult than handling it in post. To me this is likely one of two things: a very well done composite image or selective black and white in the background.------Network issue with Ubuntu 14.04.3 in Hyper V environment / not running stableAfter I had reinstalled 14.04.2 on the pysical PC and just made apt-get upgrade (not dist-upgrade), everything works fine (the login screen shows 14.04.3, but the kernel is still 3.16.0.30).I made the same steps on the VM and there it works fine, too.So I think the problem is part of the kernel (3.19) which is installed from the 14.04.3 installation ISO file.------How does a CPU calculate on a hardware level? closedThat's a good question, something I'm curious in learning more about myself. From what I can tell so far:I think these links might help explain more in case I didn't answer your question the way you wanted. htm.
Can I Take Any Blue LED Lamp and Grow?or Are There Some LEDs Special for Growing?
yahoo search is a good tool for that question1. Voltage, Current, LED lamp question...?Where did the 50 amps figure come from? (You are not confusing it with 50Hz, are you?) To drive a current I down a LED with forward voltage V, a rule of thumb is to start with a voltage 4 times V, and connect the LED on series with a resistor 3*V/I. Yes, just a rule of thumb. The forward voltage quoted is only a typical value, and will vary from one LED to the next. Using a higher supply voltage and a series resistor keeps the current more or less constant despite variations in the forward voltage.2. How to find current and voltage requirements of an LED lamp / strip using a multimeter?Attach the LED lamp to a power supply and ramp up the voltage until it is acceptable bright. Record the voltage and current. That is your new rating.You can not tell the actual rating with knowing the ratings of the parts inside and how they are connected. The packaging can even influence the rating if it can not keep the parts cool.3. how can I make a regulator of some sort to protect my led lamp from burning out?There are ways to convert 12 volts DC to 6 volts DC, but the right thing to do for this sort of project is either to get a light that is natively 12 volts, or a battery that is natively 6 volts. Google "12 volt LED light" and you will see many4. LED lamp - connecting LEDs in parallelThere are plenty of LED lamps that do not have current limiting resistors and rely on the LEDs being equal. This often is not a problem or not seen as a problem.The LEDs might be "equal enough" for the current to divide itself properly. Maybe the current is not exactly divided equally but as long as the difference in the current through the LEDs is not too small or too large, the difference in currents is not a problem.The LEDs themselves have some series resistance.With many LEDs in series, differences in forward voltage will "average out" reducing the difference between LED strings.Is putting a series current limiting resistor for every string and using CV source a more robust solution and why not do it in this way?Indeed this would be a more robust solution to add current limiting resistors.The reasons why this is not always done might be cost (a resistor cost money and might take up valuable space where there could be an LED). Also: it works without resistors so why add them?5. Does LED lamp gives protection to our environment?No. Even a perfect lamp that produced only light does not "protect" the environment. All it does is damage it less than any other type of light does. It still uses power, which means you need a power plant, which produces pollution and greenhouse gases. .6. LED and lamp in series - why does the bulb not light?The LED drops so much voltage that there is very little left for the light bulb.You have only two 1.5V batteries, which, in series, are barely enough for the LED forward voltage.Incandescent bulbs quickly go dim when the power which they dissipate is reduced: power is voltage squared, divided by resistance. For this very reason, dimming incandescent bulbs does not save much energy. Only a small fractional decrease in the dissipated wattage dims a light bulb almost all the way.Filaments generate mostly heat, and only a small fraction as visible light. This is very sensitive to temperature, which is very sensitive to dissipated power.Try looking at the lamp in a dark room; you may be able to see a faint red glow. Also, the light from the LED may be preventing you from seeing whatever dim glow the bulb is putting out, even in a dark room. Cover the LED, too.7. how to install a led lamp inside mouth?A miniature LED, if connected with a tiny 1.5 volt button cell,properly, u can keep it well into ur mouth.but with uneasiness8. LED lamp increased power consumption after installation: Why? [closed]With the limited information provided, this is a guess, and a suggestion for clarification, but... Where did you get consumption of 2W per lightbulb from? Those are simple LED's, no special drivers or current limiters included in the package. If you have them in a series string, you need to limit the MAXIMUM forward current for the entire string to 150mA (from the datasheet as absolute max If). You can not do this just with a voltage source, and for a series string, I would not attempt it with a single resistor either, use a current regulator.If you have them in parallel, you can use a series resistor with each individual LED, based on your supplied voltage, to limit its current.The wild guess/speculation part is here... I am thinking that without proper current control to the LED's, you are burning them out, and they are failing as short circuits causing more current to flow as the voltage drop across failed ones vanishe.
How Can I Project a Clear Light Shape on the Wall with an LED Lamp?
Focusing the light requires some tinkering. The size of the hole is a factor. The distance between the light source and the apeture is another factor. Also, if you are using multiple LEDs then there will be multiple stars per hole; each LED will make a star. Some words to google might be diffraction, interferance, and apeture. Also you could perhaps pick up some info from making an eclipse viewer1. Can I take any blue LED lamp and grow?or are there some LEDs special for growing?yahoo search is a good tool for that question2. Can you convert a halogen lamp to a multiple LED lamp and still get comparable luminous flux?Your biggest problem will be heat dissipation. High power LEDs dump a lot of heat down their cathode leads. If you do not keep the LED's cool enough they will degrade and die early. So you need to design for heat sinks & air flow; which brings up the next problem. Halogen bulbs are designed to run hot, so the fixture probably was not designed with air flow/heat disapation in mind. So figure on modifiing the fixture for improved air flow.3. can we get lesser power consumption if we use LED lamp?LEDs are small, very efficient solid bulbs. New LED bulbs are grouped in clusters with diffuser lenses which have broadened the applications for LED use in the home. I like INNORI Eye-protected Touch Sensitive Dimmable LED Desk Lamp,3-Level Brightness for Different Occasions. LED technology is advancing rapidly, with many new bulb styles available. Initially more expensive than CFLs, LEDs bring more value since they last longer. Also, the price of LED bulbs is going down each year as the manufacturing technology continues to improve.4. Can kitchen salt break a LED lamp circuits/board? (weird problem) [closed]Specs: YN600 Air adopts double mains input,which supports batteries of NP-F Series external DC main of 8V and 5A. YN600 Air adopts YONGNUO proprietary LED constant current driving technology There is also a 12V 5A supply.----You are seeing failures with the line voltage AC to DC converter not the 8V constant current.The salt must be completely removed with a good quality isopropyl alcohol with several rinses and then forced air dried for many hours to ensure no moisture under chips. The LEDs are still good and you can run from 12V.They use salt to boil water rapidly with just electrodes at line voltage and will fry the converter if used again and not carefully cleaned of all salt ions which will not be easy and may consume a bottle or two and require vacuuming.Salt is corrosive and it may be easy to destroy it. So look for YouTube videos and chalk this up to experience.5. can you use sally hansen gel polish without the LED lamp?no it is not possible the chemical in the polish is specifically made to cure with the led lamp. if you let the polish not cure and it just dries the chemical that makes the shine last might still be active and if you eat finger foods like chips and such you might ingest the same chemical because it was not cured with the led bulb6. Story problem: you leave the house for a weekend, accidentally leaving a 3W LED lamp on for about 36 hours. If you pay $0.11 per kWh for power, how much money have you wasted by leaving a light on for two days?3*36= 108 W or 0.108 kWh *.11= $0.01188Story problem: you leave the house for a weekend, accidentally leaving a 3W LED lamp on for about 36 hours. If you pay $0.11 per kWh for power, how much money have you wasted by leaving a light on for two days?7. Why does my Betta fish puff out it's gills when I turn on an LED lamp?Maybe the time is too long,u need to know something anout it8. Does LED lamp gives protection to our environment?Neither our environment nor financial growth ought to be put in front of another. we are no longer speaking approximately oil and water, interior the sense that they can not mixture. in reality, Sustainable growth has been utilized via industry for some years. The evidence is interior the pudding, that sustainable growth works! Lumber agencies now want to diminish sensibly, rather of clean slicing a close-by. chosen timber are decrease, mutually as others are left to enhance, new ones are planted as against the felled timber. this way, the lumber agencies will continuously have product to reap. This additionally minimizes, yet does not thoroughly get rid of erosion of soil, or habitat loss. inspite of the shown fact that, it is a lot extra advantageous than the alternative... clean slicing. in reality that people might desire to proportion this international, we are able to depart a footprint no remember what we do. inspite of the shown fact that, minimizing that footprint will depart the two us and our environment in an superior condition. To think of that economics ought to be positioned on the lower back burner is only naive. without financial growth, how can you grow to be knowledgeable? shuttle? How will people locate out approximately our international, and grow to be extra advantageous stewards of the earth, if we are all out of a job and ravenous?? it is a provide and take relationship that people have with our environment. we would desire to locate the stunning stability between provide and take
Suitable Wiring for Very Low Current Mains Equipment
Mains cabling doesn't just have to supply power to your lamps; it also has to be safe in the event of a fault. If your lamp short circuits, you don't want the cable to burn out or start a fire before the fuse blows (if you're in a fused plug country like the UK) or the breaker trips! So standard 3-core mains cable probably is appropriate. See also MandoMando's comment on the correct insulation. Or as Dave Tweed says, use low voltage lighting and a mains transformer (perhaps look for garden or outdoor lighting systems)EDIT: if the rest of the installation is up to "double insulation" standards with no exposed metalwork, then 2-core mains cable would be acceptable, saving some spaceI'm building an interactive portrait gallery with seventy portraits, each back-illuminated by an LED lamp. The lamps draw less than 30 mA at 230 Vac, and each is switched using a small optocoupler/phototriac, under microcontroller, er, control.Given the very low current draw of the lamps, standard 3-core mains cable seems to be considerable overkill. (All of the wiring will be hidden within the gallery structure, out of the way of prying fingers; we have a mains bus, from which I can tap the connections for each lamp.)Would a three-strand section of ribbon cable be up to the job? Some specs I've unearthed are rated to 300 Vrms (and up to 1 A), which would seem to be suitable. But what consideration would I have to give to voltage spikes?I want to build something safe, but a lighter cable would make construction much simpler.
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