trend in low-power coloured LEDs?

Dave_H

Flashlight Enthusiast
Joined
Nov 3, 2009
Messages
1,346
Location
Ottawa Ont. Canada
I like to fool around with low-cost LED devices...flashlights, night-lights, small lanterns and battery-powered strings, etc. some of it being dollar-store grade, but what the heck.

Over time I noticed more strings using multi-colour LEDs changing from pure colour LEDs, to all white LEDs using coloured lenses over them. This makes the colours washed out, red especially anemic. It's easier to manage the current limiting; only a single resistor for a bunch of LEDs in parallel which have similar forward voltage, compared to wide variation with different colours (separate resistors).

Now, looks like they are using white LEDs with internal tinting, possibly coloured filter over the die, inside the package, as body plastic is clear. Green and orange are brightest, blue is dim and red very weak. Looks horrible.

I checked forward voltage on what should be orange LED and measured ~3.2v, which smells like a white LED to me, plus is has whitish tint. Typical orange LED is 2.0-2.5v .

Anyone else notice this, and what's the story on it?

Dave
 

Dave_H

Flashlight Enthusiast
Joined
Nov 3, 2009
Messages
1,346
Location
Ottawa Ont. Canada
Microscope examination of orange LED with high V(f) confirms orangish material covering the die, tinted plastic or
possibly contains orange phosphor?

I checked spec sheet on typical orange SMT LED. confirmed 2.0-2.5v V(f) at 20mA.

Cheap yellow string from the dollar store showed V(f) 2.0v at modest current, at least this one is a "real" coloured LED.

That said, Christmas lights have appeared in some stores. In Ottawa it's going to +31C today, "humidex" up to +40C;
summer in (nearly) October.

Dave
 
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