How about a 120v/240v direct AC version? - (rectified first)
I'm sure Ghurd will be interested and a good help - he has kindly helped me before in all matters LED.
Ben
Thank you for your appreciations. As a matter of fact, yes, I do enjoy what I do. From time to time, that is. This is a hobby of mine, hence the patience.
I would certainly be interested in 240V AC versions. Unfortunately the LED array calculator I found can not calculate voltages that high. I know Ac has to be rectified first, but it's that capacitor and resistor that makes me wonder. Such a LED conversion could be made using GU10 halogen bulbs as it has enough space to allow all the components inside its base. Actually i'm just guessing here, I never opened one up.
I'll send the link to Ghurd maybe he'll be kind enough to make his advices public here. Being a great guy, he usually is.[ Parent ]
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 ]
My post was sent twice. I went to check for any errors, I corrected them, and when I sent it, Yahoo reported as sent already when I sent the second, I went to see if such have occurred and it did, showed two posts.
I am wondering that there is a glitch in Yahoo group software.
I concur with Amanda's statement regarding the resistor values, voltage, and 3 LEDs per string. A just charged battery will have higher voltage and the current will rise dramatically. I usually design for 18ma at 14.4V.
Simple line powered LED bulbs are a problem. For 120VAC, it could handle 50 white LEDs in series. 220VAC could handle 100 LEDs. The problems are, if one LED fails to an open state (common) the bulb is shot, and if one LED fails to a shorted state, the voltage rises on the other LEDs, raising the current, leading to more LED failures.
Line power into LEDs could often be better utilized. The 20ma at 120VAC is 2.4W, and 4.4W at 220V. A CFL gets my vote for better use of power and longer life than very long strings of LEDs.
LEDs can be line powered other ways, but it can get complicated. The losses get higher and there are more parts to fail. Personally, for grid powered LEDs, I would prefer to grid-charge a battery for the LEDs. It's easier! G- [ Parent ]
Ok, ok, I got it. I overrun the LEDs a little. Next time i'll be more cautious. They were cheap anyway :-)
I got the point that line powered LEDs are not such a great idea. But what about the commercial bulbs? How are the made? I never opened a 220V one so I don't know what they use in terms of electronics. There has to be some better way of using line powered Led's as the LEDs business over here starts to grow dramatically.
I see building lighted with leds, I see commercial signs illuminated with LEDs too...
Here's my LED supplier. The page is in english too so it should be easy to get my point. http://www.zexstar.com/english/index.php?cat=26#[ Parent ]
The saddest part is the owner bought it to run it from a 12V inverter. G- [ Parent ]
I'll head for the fluorescent department now. No more fancy 220V LED bulbs anymore. In fact, I did made some fluorescent inverter bulbs for 6 and 12V but they were a little power-hungry for my taste. The consumption depends on the light output. It's all about a pair of resistors. A 12V/0.5A bulb I made will give enough light to stop you from bumping into things but if you really want light, 0.8-1.0 Amp/h is the way to go. This also comes with heatsinking so bye bye economy.
Yes, it's sad what that owner did. I imagine that bulb wasn't cheap. I feel sorry for him. [ Parent ]
Vawtman, I never saw those bulbs. I would not have much confidence in the warranty unless the brand name is old and common. I was pleased with the factory LED strings I looked at. Makes me wonder why... they include extra LED replacement bulbs? LOL
G-[ Parent ]
I couldn't get that link to work. Check them out at the link below, 50 , 5 led bulbs for $70.oo for the c-9's. How do these compare to the ones you found?
http://www.creativedisplays.com/siteresources/modules/webstore/scripts/prodList.asp?idCategory=37
Gordy[ Parent ]
So one day i thought maybe they made c9s led bulbs and found them.Seems lots of companies(sights getting in this).Maybe the price will come down has a result.
Thanks for helping [ Parent ]
The only commercial LED sign I ever saw up close must have a supply for each LED. "Each LED" was a cluster of 3 LEDs, red, yellow, and blue. I have a closeup photo, somewhere. It is in New York City in the NBC building. This photo is not so great, but it's all I found on the internet. http://www.nbcnewmedia.com/gallery/nbcExperience/globe.jpg G-[ Parent ]
From an energy perspective it still makes sense to use CFL over LEDs. The lighting of buildings with LEDs has a high gadget-factor, but is not the best thing if you want to minimize power consumption.[ Parent ]
This is true most of the time except when just a small amount of light will do. The smallest CFLs are about 3 watts and not all of them are useful. So if low light or highly concentrated light is needed LEDs can best CFLs. John..[ Parent ]
