I need a suggestion for driving L.E.D. several series and parallel combination, to be used at voltage less than ~80V to avoid shock.
The micro controller will be used for controlling it..!!
Hello
I want to make led screen flashing effect so i use smps or rectifier which increase cost and size power i need some sort of const currrent like this
Do you want to get from 220v ac to 80v dc (regulating current not voltage)? LEDs are current devices not voltage devices.
Do you want isolation? With out isolation the LEDs will be sitting on the power line.
What power level? 40 watts?
Actually, I need chip for constant current operating at line voltage will be also fine.
because at more voltage you can make large string less wire nest.
in slide you can see this type of led screens **broken link removed**
The PDF. that I pointed at is constant current, but it is built for a light bulb.
When I made LED signs each LED was addressable. (each LED could be turned on/off, color, brightness) There was no string. They ran from low voltage DC. **broken link removed**
This picture (below) is probably the only one with a string of LEDs. The link in post #9 will do this job. **broken link removed**
Anyway, I found one thing more in L.E.D.'s that in string most probably one LED gets OFF and rest remain in working condition. why it happens to LED, what is reason behind it it should break all all but it passes current rest remain ON.
If a LED fails short-circuit it will pass current to the remaining LEDs. If you are not using a constant-current source as the driver then the remaining LEDs in the string will get more current than before, so will be more likely to fail.
Usually when an LED fails it does not conduct. In a series string then all LEDs do not light.
A semiconductor manufacturer makes an IC that detects a non-conducting LED because it has a high voltage across it then it shorts that LED allowing the remaining LEDs to light.
Usually when an LED fails it does not conduct. In a series string then all LEDs do not light.
A semiconductor manufacturer makes an IC that detects a non-conducting LED because it has a high voltage across it then it shorts that LED allowing the remaining LEDs to light.
My Brain needs to understand why does it happens, and how to detect the LED we are using is fine..which chip are you talking.
really curious to know more about LEDs
My Brain needs to understand why does it happens, and how to detect the LED we are using is fine..which chip are you talking.
really curious to know more about LEDs
One of the semiconductor manufacturers makes the IC that detects a burned out open circuit LED and shorts it so that remaining LEDs in series with it continue to light.
All the traffic lights in my city use LEDs and I can see burned out LEDs in some of the lights. Each traffic light color has many LEDs so they are probably all in series. They must use that IC that shorts the open LEDs.
Most of the street lights in my city also use LEDs that are also probably in series. They are controlled by a modem with a little antenna on top, instead of being controlled by an LDR.