HP Forum Archive 19

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Curious question (OT): Green LEDs? Message #1 Posted by Maximilian Hohmann on 23 Feb 2010, 6:01 a.m. Hello! Just a curious question: Many sellers advertise calculators with fluorescent displays as "green LED". I have seen several desktop calculators that really have green LED displays, but never a pocket calculator. So: was there ever an LED pocket calculator with a display colour other than red (like green or yellow)? Some Sinclairs have violet/purple filters over their red LEDs, but that dosen't count... Regards, max

calculators: no Message #2 Posted by Frank Boehm (Germany) on 23 Feb 2010, 6:56 a.m., in response to message #1 by Maximilian Hohmann At least not to my knowledge. I think there were some hefty downsides (prohibitive expensive?), probably no driver ICs existed, requiring a transistor based driver (too large and too expensive). There were one or two LED watches using green LEDs - extremely rare and sought after, because they were expensive back then :)

Re: calculators: no Message #3 Posted by Thomas Radtke on 23 Feb 2010, 8:52 a.m., in response to message #2 by Frank Boehm (Germany) Green LEDs were invented in the 1970th, so they were not available for the first pocket calculators. I might be wrong, but due to the smaller wavelength they probably consume more power. This, and the fact that at that time vfds were spreading, would have made it not really attractive for any company to switch from red to green displays.

Link of green LED watch Message #4 Posted by Frank Boehm (Germany) on 23 Feb 2010, 9:06 a.m., in response to message #2 by Frank Boehm (Germany) Green LED watch

Re: Curious question (OT): Green LEDs? Message #5 Posted by Ron Ross on 23 Feb 2010, 8:14 a.m., in response to message #1 by Maximilian Hohmann Yes, there were some green LED calculators. My first calculator was a Radio Shack 4 banger (Casio derivitive) and it came with green LEDs. It was a quality Casio calculator and used 2 AA batteries.

Re: Curious question (OT): Green LEDs? Message #6 Posted by Thomas Radtke on 23 Feb 2010, 8:53 a.m., in response to message #5 by Ron Ross Do you remember the exact identifier?

uh, *no* Message #7 Posted by Frank Boehm (Germany) on 23 Feb 2010, 8:59 a.m., in response to message #5 by Ron Ross Casio used LEDs for less than a handful calculators (I own 3 different, and I doubt there are more...) and moved as early as possible to VFDs (already in 1972 with the MINI!). So your Radio shack used (green) VFD...

I stand corrected. Message #8 Posted by Ron Ross on 23 Feb 2010, 10:06 a.m., in response to message #7 by Frank Boehm (Germany) I stand corrected. You are correct.

Re: Curious question (OT): Green LEDs? Message #9 Posted by Philippe Lasnier on 23 Feb 2010, 8:23 a.m., in response to message #1 by Maximilian Hohmann I suppose that there were genuine green LED displays used in calculators, but most of the time the descriptions you refer to are given by ignorant people, or people who don't actually care that their description should be technically accurate..."LED means 'display' , right? and it's green-ish..." On the same subject, how many time would you have seen plastic pouches and cases advertised as "leather"? It seems a lot of people don't know the meaning of the word... Phew, it felt good to let that off my chest ;-) Philippe

Re: Curious question (OT): Green LEDs? Message #10 Posted by Eddie W. Shore on 23 Feb 2010, 9:02 a.m., in response to message #1 by Maximilian Hohmann I had one with a green LED. I think it was a bluish TI adding machine. I think I was two years old ('78/'79) when I was playing with it however. Edited: 23 Feb 2010, 9:03 a.m.

Re: Curious question (OT): Green LEDs? Message #11 Posted by Bart (UK) on 23 Feb 2010, 9:37 a.m., in response to message #1 by Maximilian Hohmann Hi Max! I remember my dad bringing home a Sharp scientific calculator, the first one i'd seen (he had a 4-banger) - I was in primary school then. I was amazed that it had an exponent function. I always remember it having a green display and thought it was LED. Having searched the internet and from my memory, it was probably an EL-502 - which has a VFD display. So, I certainly can't recall any. I'll trust the great collectors on this forum on this topic - as if i'd doubt them in any case :-). Bart

Re: Curious question (OT): Green LEDs? Message #12 Posted by marais on 23 Feb 2010, 9:51 a.m., in response to message #11 by Bart (UK) I am almost certain that what you recall as being green LEDs were all vacuum fluorescent displays. They were quite common in the late 70s, and still a sight to see, if you want my opinion. Andreas

Re: Curious question (OT): Green LEDs? Message #13 Posted by Thomas Klemm on 23 Feb 2010, 11:34 a.m., in response to message #1 by Maximilian Hohmann There's an old thread: Green LED's?

Re: Curious question (OT): Green LEDs? Message #14 Posted by Garth Wilson on 23 Feb 2010, 3:11 p.m., in response to message #1 by Maximilian Hohmann I doubt it. For many years green was the least-efficient of the LED colors. Even when blue was super expensive, it still gave more brightness for the amount of current than green did. I had a calculator (Cannon, I think) with a truly green (not bluish-green) vacuum-fluorescent display in high school. The display was quite attractive, but the calculator finished off a pair of AA alkaline batteries in about three hours-- maybe less.

Re: Curious question (OT): Green LEDs? Message #15 Posted by Kiyoshi Akima on 26 Feb 2010, 1:02 p.m., in response to message #14 by Garth Wilson Something's been tickling the back of my mind, and it finally came to the forefront this morning. No, I couldn't think of any calculators with green LEDs, but I've used cameras with green indicators in the viewfinder, and their manuals claim they're LEDs. No, I haven't taken one apart to see whether they actually are LEDs, or whether they're some other color with a green filter.

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