Identify a white LED using only 1.5 volts

Google for "joule thief" - this is how it's done.

Thomas

Thanks. Had assumed the silicon people had made a breakthrough, now I see its just a miniaturized inverter built into the bulb base.

Yeah, there's another method that is even simpler. Put two infra red LED's back to back so one illuminates the other, and connect one to the battery and the other in series. On a good day this should give you around 2.3V with a full 1.5V cell but at fairly low current.

You might have more success with an IR LED as the emitter and a high brightness red LED as the "solar cell"

Regards,

-A

Did you actually try that?

In article , testing snipped-for-privacy@yahoo.com wrote: in part:

I would expect the opposite - use shorter wavelength for the emitter than for the "solar cell". I would use high brightness red for the emitter and an infrared or longer wavelength red with a black-appearing chip as the "solar cell". Although to use with 1.5 volts requires a pair of infrared LEDs - maybe non-identical, with the emitter having the shorter wavelength or similar wavelength - but not longer. There are also LED-photovoltaic combo integrated circuits (main application is opto-isolator) and some of those could be used as boost converters - but with low output current a fraction of a milliamp. I suspect that in those, an LED shines onto a small series string of solar cells. Based on LED voltage drop, I believe the LED is infrared.

But then again, I have seen 1.5V blue LEDs of the usual 5 mm / T1-3/4 size and I believe there are related white ones. It appears to me that they have boost converters that involve switching of capacitors.

- Don Klipstein ( snipped-for-privacy@misty.com)