![]() CRTs make up most of the weight of CRT TVs and computer monitors. The face is typically made of thick lead glass or special barium-strontium glass to be shatter-resistant and to block most X-ray emissions. As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity. The interior is evacuated to 0.01 pascals (1 ×10 −7 atm) to 0.1 micropascals (1 ×10 −12 atm) or less, to facilitate the free flight of electrons from the gun(s) to the tube's face without scattering due to collisions with air molecules. Ī CRT is a glass envelope which is deep (i.e., long from front screen face to rear end), heavy, and fragile. ![]() Electrostatic deflection is commonly used in oscilloscopes. In modern CRT monitors and televisions the beams are bent by magnetic deflection, using a deflection yoke. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In CRT television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. A CRT on a television set is commonly called a picture tube. The images may represent electrical waveforms ( oscilloscope), pictures ( television set, computer monitor), radar targets, or other phenomena. This came to my mind because some years ago after discovering that a similar house was not grounded an electrician suggested to me to do the grounding to the reinforcement cages.The only visible differences are the single electron gun, the uniform white phosphor coating, and the lack of a shadow mask.Ī cathode-ray tube ( CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. This is happening in the first floor in concrete building where the house is grounded or the neutral is connected to the reinforcement steel cages between the floors and when the LED strip circuit or the COM probe from the multimeter is on the floor it interacts with the steel reinforcement cage by inductance similar to what happens in a transformer, if that is at all what is happening in a transformer. My theory that doesn't explain the whole story is: ![]() This is a first draft of answering my own question and I'm not an electrical engineer nor an electrician so it can make no sense : If anyone can improve it and link it to the LEDs and the drivers and explain how they emit even by connecting the black wire alone then I will accept that answer. Extending the black probe by conecting it to a other twi probes it reads 51 volts AC. What's going on?Įdit: Measuring the main AC voltage with the multimeter with only the red probe to the line(hot) while the black probe with its wire laying on the ground and not connected to anything gives 38 volts. It also have other tow secondary side terminals that produce dimmer light for the same source than the main marked terminals when properly connected but nothing happens when a single wire is connected to either one of them. The strip has glass buttons shaped defusers over each of the 4 leged LEDs and they don't light with one wire without removing it or maybe not visible. Try it with normal long legs red, yellow and green LEDs near the floor: doesn't work Try it with a 9v battery doesn't work(for the batery i used only 4 and less LEDs and the light is very bright when connected properly ) OK probably some mysterious EM field is causing this but maybe the strip has some hidden capacitors or capacitance behavior : Try it with the whole sketch book: IT WORKS but very dimm Try it with a paper sheet between the floor and the strip IT WORKS Try it on a wooden table:NOTHING, it works only when the strip is on the ceramic floor Trying all the above using another 18-32v 0.6A driver same result except they are now blinking at around 2 Hz The strip is about 40cm and has a clip to connect to its neighbor strip but the contacts on the clip are marked (+, -)Ĭonnecting only red wire to + the strip lightsĬonnecting only red wire to - the strip lightsĬonnecting only black wire to + the strip lightsĬonnecting only black wire to - the strip lights I was experimenting with LEDs, when I encountered the following strange behavior:ĥ LEDs on a strip simultaneously emit light when I connect eny output wire from a mean well +36V 700mA constant current power source. ![]()
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