The life span of low cost laser diodes.

[robothut]

 

[Eagle]

Kind of like ALL of the various LED lights I have installed in the house over the last 5 yrs. Most all have decreased in candlepower by at least 30% . So is it a power supply problem or LED problem ? I think power supply,,as I tore one of the lights apart bypassed the transformer and powered it with my Voltage generator...No problem..Brilliance came back.Brings up another question,,Is it possible to bridge an LED to operate on AC ?  Half Sine only.. Using a non rectified transformer power supply . Maybe lay out two parallel strips with reversed polarity ? 

[robothut]

The LEDs do degrade  over time , temp  and require more power to putout the same light power they used to have.

Most LED light drivers do not have a way to compensate for this but there are a few circuits do, they just cost more money and since the makers of LED lights want to sell more lights why would they spend more money on the power supply to make the LED lights last longer when they can sell you another light . And that is the way the world goes.

Now as far as using the LED "light emitting diode" as a diode in the power supply circuit, I think the problem is the reverse diode conduction. Normal diodes like a IN4001 that would be used in a power supply conducts in one direction and is a open circuit in the other direction of electron flow. LED's conduct in both directions. For example a standard red LED will turn ON at about 1.8 volts in the forward direction and if you reverse the current direction they start conducting again at about 3 volts only no light and if you push them then you just destroy the LED.

[Morbius]

I was told it was the power supply on my robot room ceiling light, supposedly to last 40 years, lasted just over one year and I'd have had to send it back to China to be covered under warranty.  It had around 40 LED's in like tape strips in it.  Also it gave off a greenish light, never liked it.  Installed new fixture with 2 new LED standard shape lightbulbs, these were '20 year' bulbs, one lasted one month and the other 2 months.  Installed an old  LED flat design lightbulb and one incandescent bulb into that fixture, haven't had trouble in a year or so.  The old expensive ones still are going strong, we have 2  very heavy ones in our living room I bought about 18 years ago for $35 each, no issues and don't seem to have dulled down over time either. They apparently can be made to last but as you said John, they want you out there every other month to buy the latest crappy design.  And just try to find the same one you just bought 2 months on, they always seem to be 'new and improved'.  Right.

 

[Eagle]

Mike the LED bulbs in my Mag lights are over 10 yrs old and are still as bright as ever...NONE of my household lights have ever held their brilliance over more than 6 months. As they fail,,I replace them with the old Florescent Bulbs and light fixtures. John,,have had that happen..A blown LED will give you a jolt. I was referring to running two strips with the Led's run in BIAS to take advantage to the AC current  at i.5 V AC. Never tried it..Was a fleeting thought.I don't quite believe these House lights are as energy efficient as the say they are. Those transformer rectifiers get pretty warm. My wife saw your video,,and instantly ask if we could carve Dried Gourds with one..I replied ,,of course not..

[robothut]

As far as house hold LED lights go there are 2 main types of power supplies. The isolated ones with mini transformers and control chips and the capacitive dropper type. The cap dropper type us a capacitor and a resistor to drop the AC line voltage, the do not isolate the LED circuit from the AC mains and have a poor Power factor number so are not used much. The big problem with house  LED lighting these days is all the LEDs are  in series, so if 1 LED fails they all go out, some times they make to circuits of it so if one LED goes out only 1/2 of them go out. Just like old time xmass lights in design. The more LED units you put in series the more voltage it will take to make them work so the less you have to drop the AC mains voltage.

Also the LEDs in the home lighting if you take them apart , you will find little flat square LEDs with a yellow looking center. Those are groups of LED's inside each square unit. A single LED inside that group can fail as they are all in series as well. You can normally see when one of the LEDs in the square flat pac has failed by a small black dot. That black dot is what is left of the LED that failed. But non of this has anything to do with laser LEDs. They are a different design.