Joule Thief

[MarkE]

That is correct.  You can screw those bulbs into a light fixture and run them on 120, or place into my circuit and run them at around 400.  The lights of America have no electronics inside, so no need to modify.  Most of them are 27 chip leds and I have some that are 24.  Now, when I use the Cree 40 watt equiv. bulbs in the same circuit, I have already removed all of the electronics and am just using the leds.  I have hundreds and hundreds of hours on those LOA bulbs and all of them still work great.  Much brighter than lighting a gutted cfl.

Even running 2 bulbs of the LOA style led bulbs with 27 chips each (Like the one next to my bed) I am only drawing 150 mA's.

Bill

OK so you've got a series string of LEDs without any current limit resistors, or with one or more current limiting resistors?  These are nominally 3V white LEDs?  And the 150mA draw is from a single D cell?  Do you have any oscilloscope captures of the LED drive waveform?

[Pirate88179]

OK so you've got a series string of LEDs without any current limit resistors, or with one or more current limiting resistors?  These are nominally 3V white LEDs?  And the 150mA draw is from a single D cell?  Do you have any oscilloscope captures of the LED drive waveform?

No resistors or anything else in these bulbs.  The amp draw was tested from an AA battery, but I use a D cell in my reading light so it lasts longer.  So far, I have not had to change it.  I don't know how the chips in the LOA bulbs are wired...probably series but I can not confirm that.  No scope shots of the circuit as I was told several years ago that the high voltage could damage my Tektronix 2213.  I am not good with my scope so I played it safe.

TK has one of these circuits that I sent him, we could ask him if this can be safely scoped.  All I know is that I bought about 8 of these lamps 4-5 years ago and all of them are still working great.  I also made lights for my daughter, and some of my friends and all is still well with them too.

Bill

PS  I see that this is an old photo I had on file.  All of my bulbs have a standard Edison base, but this gives you an idea of what they look like.

[Pirate88179]

Mark:

Also, the driver is nothing more than a modified flash camera circuit.  I bought about 90 of them surplus for like $.40 ea.

Bill

PS This photo matches most of my bulbs.

[synchro1]

@Pirate88179,

That's beautiful. I broke one of those bulbs and examined the circuit at the base. There're several standard componants, capaciitors inductors etc. I'm sure it rectifies to DC. My tests confirmed that additional bulbs generate light more efficiently. Adding two additional bulbs would probably deliver the same amount of light for 100 ma instead of 150 based on a savings factor of 17% per additional bulb.

[MarkE]

@Pirate88179,

That's beautiful. I broke one of those bulbs and examined the circuit at the base. There're several standard componants, capaciitors inductors etc. I'm sure it rectifies to DC. My tests confirmed that additional bulbs generate light more efficiently. Adding two additional bulbs would probably deliver the same amount of light for 100 ma instead of 150 based on a savings factor of 17% per additional bulb.

It doesn't work that way.  The I²R losses per bulb go down dramatically when adding bulbs, but then the number of bulbs wasting energy in their individual I²R goes up.  Unless one starts at a point where they are kicking the snot out of LED to begin with, the efficiency gains had by paralleling more LEDs quickly hit diminishing returns.