I love LEDs a lot, and even more if it was in a Tricorder. And this was what got me through as an Engineer (barely). In those days, the only LEDs I could ever get was the normal dim 5mm reds, greens and yellows. Then came the ones in 3mm and later on, instead of the diffused milky white lens, came the clear lens. By the turn of the Century, the whites and blues arrived, paving the way for other phosphorus coated LEDs such as pink, purple and so on. Then we have a much stable flashing LEDs, the ‘candle’ version, followed by the slow and fast ‘rainbows’ (OK, RGBs), and so on.
In less than half a Century, LED technology has evolved greatly to the point that it is now more common and an essential part in a lot of products. But I am not going to talk about that. I want to talk about my bi-colour LEDs.
They have been around for a long time and they come either with a two leaded version or with third separate anode or cathode lead. At that time, I tend to overlook them because of their limited choice of colours such red/green, yellow/green combinations. These pre-RGB LEDs were used as panel status indicators or when I was an Engineer, as part of polarity tests. They are great solutions for when you need more than one colour in the same spot. You can imagine how much space they save on a control panel.
POST MILLENIUM LED SMORGASBORD
After the Millenium, I discovered I could order things from China, and direct from the Manufacturers. But that was a real needle in a haystack as many Manufacturers insists on 5 figure MOQs. Still, I am not sure if it was my doing, but a few months later after my order arrived, new bi-colour LEDs came out on the market with the exact colours but in different formats.
Anyway, this is my latest bi-colour LED, which is a green and blue in a 2mm x 5mm x 7mm rectangular shape. Some call them as 257’s so you have to be very precise with the search keywords. There quite a fair bit of these LEDs out there, both i different colour combinations and forms. But alas, the ones that I need does not always exist. And I needed them with clear lens and not diffused. Still, today’s choice was as close as I can get.
BI-COLOUR VS RGB
There are two ways to get colours out of an LED. The best way is to get the bi-colour LEDs. But you cannot choose the colour combinations though. Which is not an issue if you can get in touch with a LED manufacturer and agree to their conditions.
The other way would be to use a microcotroller and RGB leds. Using PWM programming, you can mix the three separate LEDs (Red, Green & Blue) to create any colour you need. But there is a disadvantage’ apart from learning programming and all the microcontroller tools, you have to make sure the colours combine. Different RGB LEDs have different issues because of the three separate LEDs inside it.
And, with some PWM programming, you can get more colours between the blue and green range.
And running at 10mA, they are very, very bright.
