Illumination!

Hi there-

I have a bit of a beginner subject and I’m not exactly sure where to look for more information. I’m using purple LEDs, with the hope of lighting up a rectangular space - about 7 inches long and 5 inches wide. The LEDs do not seem to illuminate anything beyond themselves - they don’t seem to cast much light. These LEDs were spec’d for 7,000 mcd on eBay.
Is this just how LEDs are? Would a different color behave differently? What about things like reflector plates and LED strips? How can I better understand this subject?

julieCabazon:
These LEDs were spec'd for 7,000 mcd on eBay.

So where's the link?

What I think, they are not purple, they are UV. So they might produce 7000mcd but without something UV-reactive you don't see it. And most of those UV leds have a tiny bit of UV reactive component in the plastic shell. Hence why you see them glow.

http://www.ebay.com/itm/390924546738?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I think you are right!

The listing tells you, UV leds. So if you want purple you have to buy purple :smiley: Or make the object UV reactive. UV light on a bright white paper gives a purple-ish light.

Careful! You could actually get skin burns with an array of those things or damage your eyes with just one!

Do they make purple LEDs? It seems like most of what turns up is UV. Maybe my search terms are wrong.

There are pink ones. Is that close enough?

You can also get red-blue bi-colour leds. These could be wired up to give colours in the purple-magenta range, by adjusting the series resistors. If drven by an Arduino, you can use pwm to adjust the colours.

Another option would be to use ws2812b leds, also known as "neopixels". These can be programmed to show almost any colour. They are also bright and have a wide viewing angle. But, they need to be connected to an Arduino to tell them what colour to display.

They do make purple and pink. I have both here. Yeah, the are both a bit harder to find. (Can't find where I bought them now :confused: )