LED Lightbulb

[SmokinJoeR]

How does a LED lightblub that screws into a standard lightbulb socket work? Is there a brige rectifier that changes the 120VAC to some DC voltage and then the LED's are connected in series for an appropriate voltage drop?

Following Link is an example of the product I am discussing

http://www.ccrane.com/lights/led-light-bulbs/index.aspx

Any help is appreciated

-Joe

 

[MacGyverS2000]

Typically a SMPS of some form or another is used...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

Not in the $350 LED floodlight I have.

It is just as stated.

Rectified AC fed directly to 62 LEDs in series if memory serves.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[VEBill]

"...62 LEDs in series..."

Didn't the human race learn anything from the misery of those old-fashioned series-connected Christmas tree lights?

 

[PeacefulKancer]

Nah, if you get the specs right for the LED series then you should be good due to LED reliability/lifespan.

 

[VEBill]

(This is a bit of an old thread...)

The only way these LEDs will ever become a mass market item is when they're made in China and do not cost $350 each.

Based on reviews I've seen on websites selling early-generation LED lightbulbs (made in China), the failure rate is not yet acceptable. I'm as early an adopter as anyone, but I'm not buying LED lightbulbs for my house just yet.

 

[itsmoked]

Well I dug up my gold plated LED flood light and it is actually broken into three groups, each with a dip full bridge, a resistor or two, and a couple of electrolytics.

But as that was bleedin edge stuff the link the OP put up has some MUCH less expensive units that I suspect are XXXXX times brighter.

You can go either way. An SMPS or rectifiers. I'm sure the rectifiers are far cheaper and possibly more robust due to far lower parts count but they may not be as bright due to lots of ripple. (hic)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[drillz]

Hi,

I used to test LED lighting products at work and the problem is, as you say, that they are too dim...or rather, they are bright but only in the "zenith" direction.......to get them spraying light around more you end up having to use too opaque diffusers.

I once switched a nine Watt LED light on with no diffuser(contained about 80 LEDs) whilst holding it about a yard in front of my face.....it was painful and i never did it again! - i can stil see the flash in my mind's eye.

To get round the problem of blowing one LED in a long series chain..........put suitable value zeners across series lengths. -current can then divert via the zener if one blows.

Of course, the beauty of LED lighting is precisely that it is dim, -and can provide nice "mood" lighting if done right. Also, as you know they can be switched on/off in colourful patterns.

 

[MacGyverS2000]

To get round the problem of blowing one LED in a long series chain..........put suitable value zeners across series lengths. -current can then divert via the zener if one blows.

...which then blows, followed by the LEDs in short order.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

That would be my guess too.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[drillz]

Hi,

The idea of putting zeners across series sections of LEDs was shown to me by the Senior Electronic Engineer at a fairly large lighting company. (-they make warning beacons etc). This was at an interview. He asked me what the zeners were for and i said to stabilise voltage....he then replied "no"...but that the zeners were to keep the remaining LEDs lit if one blew. .....it was a long series chain of LEDs.....and every series length of some 10 LEDs had a zener across it.

 

[MacGyverS2000]

...and every series length of some 10 LEDs had a zener across it.

This is a somewhat different case. Originally it was a single string of LEDs with a single zener... if an LED goes open, the entire current for the string runs through the zener, resulting in a popped component. The onyl was to prevent this is to run a very large zener to handle all of that power, not something you're likely to see in a 120V object.

In the most recent case you mention, each smaller string has a significantly smaller power requirement, so if a string goes open the corresponding zener takes up the load... but it's a much smaller load, and therefore is reasonable to assume it will continue to operate.

Dan - Owner

http://www.Hi-TecDesigns.com