How To Get Service Hours Fast

Unstable lights

be This time of year for us countless Fairy lights hung. If you with a quick movement for so happened, as if those lights would suddenly move? This is indeed the case, but only works in modern fairy lights with LEDs, in short LED's. The priority for new packages in the stores almost everywhere on it, there's the old light bulbs any more. LED is the acronym for "light-emitting diode", ie light-emitting diode. One has to observe the effect, not even turning his head away, it is enough rapid eye movement on the lights, where you should look to do anything specific, but "fly over" just only pretending.

a) photograph of a chain of lights on a tree with fast, angular movement of the camera with a long exposure time - the pulsed light is clearly visible. b) Even faster movement so that the light pulses are drawn far apart. The continuous strip between them originate from the reflection of a street lamp.

The lights, the LED's are almost always used in alternating current, as it would be consuming a lot in the power supplies generate a proper DC. The LEDs are real rectifier diodes, which convert a good portion of the released energy into light. But just as the so-diodes themselves have only one current direction. In order to still utilize both directions of alternating current, as a compromise with the LED lights (at least in that I have ever seen), is installed in the cable of a bridge rectifier. There the flow is reversed, that of the positive and negative half-cycles are positive then louder and then the current flows only in one direction. But as it direct from the 50-Hertz alternating current is generated, it goes after each half-cycle back to zero and then changes to 100 Hz - and that's what you see in the fast-reacting LED lights.

Traditional light bulbs are even slower. For them, the metal filament until it glows and cooled after each current half-wave so slowly, and the emitted light decreases only slightly to the heating followed by the next half cycle. When the LED's is different, they are very fast because the light generation is not due to heating of the material. The electrons in the interior, causing the current transport come from a high energy state (conduction band) in a low energy state (valence band) down and the difference in energy is directly converted into light. This process works even when the LED even at temperatures far below room temperature cooled.

This raises the question of why the pauses between the phases of a light emitting diode, which is operated with a rectified alternating current, so long. This is because the voltage reach to the LED's in each half-shaft has a relatively large value, before the current passed through and light is produced. How to get out the right diagram above recognizes the LED is about half the time light and half dark.

The temporal variation of light intensity was placed at the pictures above by a rapid movement of the recording device in a local variation in order to make them visible in a photo. You can also go another way by the camera can stand still and move the variable light intensity in the receiving area quickly. In the left photo below I have the end of the LED light can circulate in the wrist.

a) The end of the light chain revolves around the wrist, you can see very beautiful the light and dark phases of the LED lights. b) For comparison, a rapid movement of two alternating current (white) and a battery-powered (blue) LED - the difference is obvious.

Also see it very well that during the circular motion, the LEDs light up about half the time, or dark. Due to the changes in brightness of 100 Hz, resulting from the 12 stages of brightness LED, an exposure time of 12 times a hundredth of a second, or 0.12 seconds. During this time, almost a half circle movement is performed. A complete revolution would have taken 0.25 s, yielding four circular movements of the light chain per second will give.

The whole effect is observed only in LED's that are actually operated with polished, AC. When the AC is smoothed by capacitors or even LEDs supplied by direct current from a battery are then "stutters" the light is not natural. This should also be checked. If a theory allows a test to rebut it can, it should be carried out. In the right photo above the camera quickly with two AC and DC power LED has been moved over. The DC-powered, just back from a USB port powered LED shows no interruptions. The rapid movement of a normal light bulb of a ceiling lamp was due to the thermal inertia of any visible brightness fluctuations (not shown).