Nando [ Parent ]
Yes, I do need assistance for 240V but I wanted to take a ready-made bulb abd modify it for AC. Take for example the bulb I made here. It has 22 LEds of 20mA & 3V each. There are 5 strings of 4 leds and one of 2. What will I need to use it with AC? I assume I will have to make another wiring but how many should I fit on a string? I wouldn't want to make a single string of all these leds since if one fails, all of them will.
Claude[ Parent ]
It is hard to do something common for many at the same time.
Several strings of LEDs to have light if one string fails presents problems in a simple design because from the beginning 3 strings maybe needed ( 3 separated systems).
There is another solution with limited capabilities and it is a single string with a capacitor to limit the current and a group of transistors ( behave like SCR's) to short circuit damaged devices (it does complicates the design a lot).
It is best to insure that the LED's have the limited current stable for maximum life.
3 strings can be made in parallel and fed by a capacitor to avoid having a transformer IF an Integrated circuit is not warranted or desired.
SUPERTEX produces several types of Integrated Circuits specially designed for High Voltage AC driving strings of LED's
So what is the decision ?.
From a reusable energy point of view, the 12V version should be enough. As tecker said, 7812 is cheap enough and that solves the variation problem. For small solar arrays this should be the choice for lighting. 22 LED's eating up a total of 2.4 Watts should please some folks. I presented here a way to make LED bulbs and that's all there is to it.[ Parent ]
