A Christmas, String Lights, Story

I bought some LED string lights before Christmas and we had them in the office, for some random cheer. The lights were mixed colours, red green and blue. They were powered by two AA batteries, and we left them on continuously for more than a week. After a while I thought some of the lights were broken but later someone else pointed out to me that only one colour remained lit.

Only green LEDs for Christmas?

Only green LEDs for Christmas?

With only the green LEDs apparently lit, the voltage measurement on the battery was 1.153 V (1.156 V with no current flowing). A fresh battery capable of lighting all the colours of LED provides a voltage of 1.311 V with the current flowing (1.325 V with no current flowing).

LEDS lit R-G-B with full voltage.

LEDS lit R-G-B with full voltage.

Strangely green LED’s are the least efficient colour, so it’s strange they would be the last ones lit…

For change in voltage, red LEDs take the least to work, and as the colour moves up the colour spectrum toward blue, the voltage requirement increases (green is between red and blue).

Approximation of spectral colours on a display results in somewhat distorted chromaticity — Wikipedia

So does this mean these LED’s aren’t really naturally green ones, and rely on phosphor filtering? Or some other technology?

Is this a problem of perception of brightness of different colours?

Logical magnets

Jeri Ellsworth has made a great video in which she explains magnetic hysteresis, and how magnetic properties can be used for magnetic storage and logic.

She fairly describes magnetic logic as a forgotten technology, but I wonder if people are looking at this again since for high end electronics since we now have not only magnetic recording media, but also magnetoresistive random-access memory.