how do LED flashlights work?

Answer 1

Below I have included an article about how they work exactly but here is a brief overview. They do have a positive and negative connection and run on DC voltage (battery voltage not power outlet voltage). When electricity passes through them they emitt light. They are becoming increasingly popular in flashlights and light bulbs for 3 reasons.

1. They have a hugely long life span. The basically never burn out.
2. If you drop them, they dont break.
3. They use a lot less energy than even florescent lighting.

Answer 2

There are LEDs in the flashlight....white ones obviously, tho there are quite a large array of LEDs with different colors, but I doubt they are used in flashlights.

When you press the button it closes a switch, which connects the LEDs with a power source, which is a battery or batteries. I don't think they use resistors in these circuits, but often you will see either 10Ω, or 10kΩ resistors in a series of 5 LEDs, but that's only when there's much more current and voltage present. That's not the case with a flashlight.

Most LEDs use about 20 mA of current, but the brighter ones use much more than that. Their brightness comes mostly from simply driving more current thru them.....in case you were interested. :)

The LEDs do indeed use much less power and are quite bright and reliable. They are now big contenders to standard flashlights now.

Answer 3

Light Emitting Diodes are semiconductor devices where electrons go from one side of a junction to another, losing energy in the process. That energy loss manifest itself by the emission of photons, and the drop in the energy of one electron is related to the frequency of the photon emitted. A small drop can for instance emit infrared -- typically used in TV remotes -- while LED with gaps corresponding to higher frequencies - red, orange, yellow, green and more recently blue -- are used extensively for displays in electronic devices.
LED with very narrow gaps, linked with high frequencies, were recently developed, and those emit ultraviolet light. A coating of a phosphor inside the LED enclosure can absorb this ultraviolet and re emit visible white light, in a process quite similar to the one in fluorescent tubes. The difference is that LED are much more efficient in their way of generating light for a given electrical power, owing to the fact they produce very little waste heat.
Thus, a LED flashlight will use one or several LED units capable of emitting white light, and the resulting unit will either be much brighter for the same power usage as one using an incandescent light bulb, or would be as luminous but while using a fraction of the power, hence will have batteries lasting a lot longer.

Answer 4

There are two different ways. They all use a battery to power a white LED. One uses many LEDs to produce a bright beam and the other kind uses a magnifying lens to spread out the light from one larger LED. The LED itself lasts much longer than a light bulb and uses less electricity so it puts out light for much longer from the same set of batteries.

Answer 5

i'm an LED flashlight freak. i could very own like 50 of them - no kidding. outstanding now i'm gazing 2 fashions that i myself like. the two could be offered at Walmart. a million) Rayovac 3 Watt LED. (Rayovac now makes them for Remington below the Remington call.) 2) Coleman a hundred and fifteen lumen LED. the two one in each and every of those incorporate pocket lights furniture that run off of normal AA penlight batteries. yet permit me permit you recognize, on the same time as they could be small and slot in a coat pocket, they actually outperform my 6 cellular Maglite (like the police use) in terms of brightness.

Answer 6

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Answer 7

I see the first two people didn’t really answer this. I’ll try to help. I assume you mean the shake up kind, because otherwise, they are a lot like regular flashlights, only the LED’s use less current.

Okay, we have a magnet that slides back and forth through a coil of wire as we shake it up. Picture the magnetic field of the magnet. It comes out of one end (one pole) and enters the other end, looping around through the space around the magnet on the way. So we can think of the magnet as sort of a natural circuit for magnetic force. We can use it as a source of power, like a battery.

Actually, generator would be a better word, because that is what we are actually doing. In most generators, the magnets stand still and the coils are rotated so that the windings of the coils cut through the magnetic field (usually represented as imaginary lines of magnetic force.)

In the LED flashlight, we are doing the opposite: we are moving the magnet past the coil. How does it work if we are doing the opposite…? Here’s the secret: it DOESN’T MATTER which one is moving, as long as there is relative motion.

The coil is composed of many windings (turns) of fine wire. As the magnet slides past it, the magnetic field is moving also, and the loops of the coil cut through the field. This forces electrons to move in the coil; we have a complete circuit, so a current flows.

Because the motion of our arm (and the magnet) periodically reverse, we are making alternating current. So there is a small rectifier (a device which only allows current to pass one way) to ‘steer’ the pulses of alternating current and get them all going into a capacitor, which acts as a storage tank. It is like having a water tank, where we pour in buckets at the top, and tap off a little water through an outlet on the bottom. The water coming out flows smoothly, despite the fact that we are throwing in big sloshes of water by the bucketful.

Now, the LED itself. It doesn’t get hot, like an incandescent bulb filament. It works by something called recombination. You can’t see it happening, but it happens inside all diodes. Whether they are LED’s or not. The rectifier I mentioned earlier is also a diode.

What makes LED’s different from regular diodes is the fact that they are treated during their manufacturing process with very carefully controlled tiny amounts of special impurities. A diode has two layers. Where the two layers meet, there are electrons flowing in one of the layers. They other layer has SPACES where electrons OUGHT TO BE flowing, and we call them ‘holes’. I’m not kidding! *You can verify all this on Wiki or some other online reference.)

The electrons flow in one direction and the holes in the opposite direction. It is like a line of cars pulled up at a stop light. When one car pulls up, the space moves backward. When the next car pulls up, the space moves backward again. Otherwise, the cars cold not move forward. It is the same with the electrons. Holes are not found in ordinary materials like copper wire, they are only found in semiconductor materials, in devices like diodes and transistors. That is what makes them so useful for controlling currents and making them do useful things for us.

When an electron falls into a hole, it gives up some energy, just like any object gives up potential energy when it falls down. Because they are elementary particles and they can only hold certain quantized (fixed) amounts of energy, the amount of energy they give off is always the same for each electron.

The first diodes only gave off heat. Not very much heat, either. That’s okay, we didn’t want them to give off heat. But as new methods of manufacture were used and manufacturers began experimenting with different materials, they discovered that some of these diodes gave off infrared waves. That’s because the first LED’s had electrons and holes which were of a certain energy. They were used for simple on-off controls, like your TV remote control.

Newer generations of LED’s can be made to emit higher frequencies of light: red, orange, yellow, etc. And the latest ones are actually like multiple LED’s on one package, and the light they give off is a combination of all colors, white light. If you can look at the LED with a lens, you may see that there is a tiny reflector. This is because the light emitted comes out of the edge of the ‘chip’ (from between the ‘layers’.)

And the most amazing part is, they have worked out the engineering and the technology to the point where it is reliable enough for consumer products. All we have to do is shake it up and it works.

24 JAN 07, 0257 hrs, GMT.

Answer 8

I would not recommend buying one mag lights are much brighter.
The LED lights one advantage is they use less power and the batteries will last longer.

Answer 9

you press the button, and the light comes on

Answer 10

http://electronics.howstuffworks.com/led.htm

howstuffworks.com has a lot of usefull stuff.