3

Blue LEDs in the cheap, practical form we know them today, arrived in the 90s; before that, the choices were red and green.

I want to say there was a time some years before that when green LEDs became cheap and practical, before which red was the color of choice, but I'm not quite sure why I have that feeling; it's true green has more energy per photon than red, but that fact alone does not say anything about dates. I do remember the Vic-20 having a red power indicator, but that could have been just an aesthetic choice for all I know.

When did green LEDs get to the point where the only advantages of red were aesthetic and ergonomic, not cost or efficiency?

closed as off-topic by Wilson, Chenmunka Sep 17 '18 at 9:50

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about retrocomputing, within the scope defined in the help center." – Wilson, Chenmunka
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    I agree with @Chenmunka; there already are similar questions on Electrical Engineering about blue and white LEDs. – Stephen Kitt Sep 17 '18 at 9:58
  • 1
    I first encountered LEDs in 1950s transistor radios. They were white or yellow. My father told me that he used them in military radios during WWII. I've seen green LEDs in the 1970s and I built kit with infra-red LEDs in the late 1970s. – Chenmunka Sep 17 '18 at 10:17
  • 4
    And BTW, for such questions it doesn't need SE - a prior look into Wiki would have shown that red ones where the first to be mass produced in the 1960s, and it took more than a decade to stabilize a process to produce something yellowish green (I still remember that phase during the late 1970, when they started to realy look green - and gained brightness to make them usable on the same board as red ones). There is a reason that SE asks to try to search first before asking. – Raffzahn Sep 17 '18 at 13:23
  • 2
    @Raffzahn Having established that we disagree on the topicality question, and noting that when data are consistent with both 'OP didn't search' and 'OP searched, but missed the answer' you shouldn't assume the former - where exactly are you finding that? I just checked wiki again and I see lots of discussion about difficulty and timescale of manufacturing blue and white LEDs, but nothing distinguishing green from red. What am I missing? – rwallace Sep 17 '18 at 23:19
  • 4
    Let’s be kind, okay? – Davislor Sep 17 '18 at 23:39

Browse other questions tagged or ask your own question.