Led Bulb

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FAQ about Led Bulb

What type of resistor should i use for an LED bulb, that is powered by a USB cable? I am making a light using a LED bulb and a USB cable. i have tried a 47k ,100k and a 10k resistor and all resulted in low lighting. Is the Resistor the problem or is it something else? and if it is the resistor, then what resistance level should i use? i got the directions on how to make the Light from this site ( http://forums.pcworld.co.nz/archive/index.php/t-52676.html ) however i am not completely sure if all the directions are right. Some pointers for LED's:
When an LED begins to conduct, the voltage increases gradually while the current increases rapidly. Too much current will overheat the LED and eventually destroy it. The light emitted by an LED is directly proportional to current through the LED. The light output from an overheated LED will soon decrease and the LED may be damaged.
The forward voltage and wavelenght of an LED are directly related, so, it is not always possible to substitute a different LED w/o changing the voltage and current.
Some LED's table for voltage and wavelenght:
Wavelenght(nm)------Voltage
565(green)-------------2.2-3.0
590(yellow)-------------2.2-3.0
615(orange)------------1.8-2.7
640(red)------------------1.6-2.0
690(red)------------------2.2-3.0
880(infrared)------------2.2-2.5
900(infrared)------------1.2-1.6
940(infrared)------------1.3-1.7
don't know blue which is also white, but not have much difference to green.
LED's specified operating current limit must be respected for longevity and that operating LED's at their current limit does not significantly produce more brillance than at 60% of their current rating and ensure long operating life for most LED's.
Use this formula to determine the series resistance:
Rs=( +V-Vled)/Iled
where +V= voltage supply
Rs= series resistance
Vled= 1.7 V average
I led= LED current
Max. current= 20 ma(most LED)
Note:
if you're lazy in determining the resistance, then try this values:
LED voltage= 3.2-3.4V
480 ohm at 12 volts DC supply
240 ohms at 6 volts DC supply
200 ohms at 5 volts(USB voltage) DC
current will be around 25 ma with 30 ma maximum

How do i make a simple LED bulb flash on and off ? I have a small 1.5v led light or bulb and i want to make it flash on and off. How do i do it? Here are two solutions. In the first diagram, if you want to flash just one LED, leave out one LED and its 470 ohm resistor:
http://wild-bohemian.com/electronics/flasher.html
Here are some more circuits, with some theory:
http://talkingelectronics.com/projects/FlasherCircuits/Page83FlasherCircuitsP1.html
Here are some that use digital logic and/or transistors. The LM3909 chip is out of production:
http://www.qsl.net/yo5ofh/hobby%20circuits/led_circuits.htm

How to make a tabletop windmill that can generate electricity for a LED bulb? Im in high school and i need it 4 a project. i need step by step instructions on how to make a small winmill that upon moving the blades, an LED bulb will glow. I dont have much money 2 spend, so I cant use anything 2 expensive. Just get a small stepper motor (you can find one cheap in places like allelectronics.com)
Glue your windmill blade directly to the motor shaft.
Hook the LED directly up to two of the motor leads (associated with one coil on the motor).
give the windmill a spin and the LED will light up.

Can anyone tell me how to make a circuit with LED bulb? I need to create a circuit of a doll house size LED bulb, battery and on/off switch but have no idea how to do it! I basically want a battery powered doll house light for something I'm making but cannot find any anywhere in the UK so I am going to have to make one! How? OK the bulb has 2 terminals or connection points for wires , so does your switch and your battery.
One terminal on each is for a live wire and the other is neutral .
Take one wire from the left terminal of your battery and connect it to your left terminal on your switch , then wire from your switch to the left terminal of your bulb , run a wire from the left terminal of your bulb back to the battery to complete the circuit .
Do the same with the right terminal in the same order and your done .
Some battery terminals are top and bottom it doesn't matter which way you connect the wires as long as both wires start one end and finish the other .
Hope this helps .

Should i replace Philips CFL with Philips LED bulb? I rent an apartment using 24W Philips CFL bulb. For the same lumen, I want to replace it with LED bulb, how many watt should I choose for the LED bulb? This is not really as straight forward a questions as you think. A lot of it depends not only on lumens per watt, but on the lighting application. A 24W CFL emits approximately the same amount of total lumens as a 100W incandesent bulb, and they are both for the most part non-directional (the light is emitted in almost all directions). An 8W LED bulb emits about the same total lumens as a 45W incandesent, but it is more directional, so it acts more like a 60W incandesent. All that being said, in most home lighting application a 10W LED should provide close to the same total lighting as your 24W CFL, and will last about 4 times longer (about 22 years for an LED and about 5 years for a CFL, based on 6 hour burn time per day.)

what kind of led bulb will fit into my 2001 integra? i want to replace the dome bulb that burned out a little while ago but i bought one and it didnt fit, it was about 1" in length and the led one was a little longer, can anyone help me out! Ebay is a great source for aftermarket led replacement bulbs. Just be careful cause there are some cheap bulbs out there so be sure to check reviews and feedback.

Can Model Wind Turbines Produce Electricity To Power An LED Bulb? I am doing a science fair project using a wind turbine. I will buy it online from kidwind.org. It's a mini one. Can you please tell me how to use it to power an LED bulb? Please include source and details! As you know, one of the advantage of LED bulb is it may working on low voltage (DC 5V /DC12V), you can produce electricity by wind turbines with DC voltage output, and then power the LED bulbs.
And you also can find some led bulbs by this:
http://www.ledke.com/products/?anclassid=8

How is the MTBF of a LED Bulb Calculated? When a LED Bulb manufacturer claims of a MTBF(mean time between failure) of 100000 hours. On what basis does he makes such a claim. Please explain in brief the process of calculating the MTBF with respect to LED's MTBF is the same for anything not just LED's ;-)
MTBF can be calculated as the inverse of the failure rate for constant failure rate systems. For example: If a component has a failure rate of 10 failures per million hours, the MTBF would be the inverse of that failure rate.
MTBF = (1,000,000 hours) / (10 failures) = 100,000 hours
Since LED's are "Solid State" devices and if they are used as prescribed by their data sheets they should last a very long time.
Most devices fail due to excessive heat or mechanical vibration. Since LED's are packaged in a "Solid" housing and generate very little heat they usually last a very long time.
But, that's not to say that if 1 million are in use that one might not fail after 1000 hours. It just means that "most" of them will not fail for a very long time ;-)
But, if you use one in a manner that exceeds the intrinsic properties of that device you will, no doubt, see a decline in the MTBF. Poor circuit design will be detrimental to any components MTBF.
If you look at automotive brakes as an example. The MTBF of most automotive brakes is 35,000 miles. But, if you live in Phoenix AZ, and always drive on the "flat" freeways you may get 50,000 miles on your brakes. Where someone living in Denver CO, and drives in the mountains all the time may only get 15,000 miles. ;-)

Why Is An LED Bulb So Much Harder to Light? I know that an LED bulb is more efficient than a fluorescent one, at least in theory. However, I have a bike apparatus that, when peddled, lights the bulbs and the LED bulb is much harder to keep lit. Would could be causing this? Is it the lower resistance in the LED bulb, or a flaw in our system or human peddling error? Both bulbs are of equivalent wattage. An LED has a minimum voltage to light it. A typical Red LED requires 1.5 to 1.75Volts, anything less and the LED turns off. The LED is not tolerant of low voltage operation, also different color LED's require different voltage levels. A white LED may require as much as 3 volts to light.
An incandescent flashlight bulb that is rated for 1.5 V generates rated brightness at 1.5V. The difference here is that a flashlight bulb will work at a reduced light output as the voltage drops below this 1.5V so its possible to see a dimly glowing bulb at a voltage of 1.0 volt or less. Same goes for a 3V flash light bulb.
It is this difference in how these two different light sources operate that is causing your difficulty. You are comparing apples to oranges and wondering why there is a difference.
Your generator is not putting out enough voltage or current at a sustained level of over the minimum voltage requirements of the LED. Meanwhile the flashlight bulb is much more tolerant of low voltage operation. So to get the LED to light you have to pedal harder NOT because the LED is consuming more current, rather you must generate a higher voltage to get it to operate at all. Generating the higher voltage is what is requiring the extra effort.
Also an LED only work with DC. The current flows through the LED only in one direction. A light bulb can work with eiter AC or DC. So if your generator is producing AC instead of DC then your LED is only working for half of the AC cycle

what would be the replacement in led type light bulb for a GU 10 240v 50w bulb? I understand the led bulbs come in 21,48,72 rated. What do I need to replace my 50w halogen reflector Gu !0 bulb ? GU10 or E27 is ok! You could see this http://www.comlite-led.com/15-led-spotlight-led-bulbs

Led Bulb is from category: Flashlights.