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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 25th Jan 2019, 12:10 am   #1
Herald1360
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Default Early LEDs

I've just found 3 NOS Fairchild FLV100 LEDs. No idea where they came from, they were just in a plastic box with a few 2N3704s and a normal looking 5mm red LED. Possibly in a job lot of odds and ends from a late friend who was an electronics tech at the met office from college to retirement. They are DIM!
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Old 25th Jan 2019, 12:40 am   #2
Lucien Nunes
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Default Re: Early LEDs

Fun! It has taken us nearly half a century to progress from that device to a technology that has won out against the most established light sources of the 20th century. To be fair to the device, the FLV100 wasn't intended for use as an indicator but as a fibre source. It's diffuse-packaged offspring, the FLV101 and 102, achieved 1mcd as opposed to the 100's 0.5mcd.

I recall the arrival of the commercial blue LED while I was at university. I bought one for £20 and we all sat looking at this clear 5mm package in a darkened room as we ramped up the current. It absorbed us for most of the evening.
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Old 25th Jan 2019, 8:27 am   #3
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Default Re: Early LEDs

I remember the RS rep introducing LEDs to us way back, not sure of date possible in the 60s?
Cheers
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Old 25th Jan 2019, 10:01 am   #4
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Default Re: Early LEDs

I had a big bag of yellow leds scrounged from somewhere. They were pretty dim no matter how much current I stuck through them. Just about bright enough as a panel indicator in a darkened room. I've just remembered - they came from Bi-Pak in the early 70's. I think.
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Old 25th Jan 2019, 10:15 am   #5
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Default Re: Early LEDs

Quote:
Originally Posted by Lucien Nunes View Post

I recall the arrival of the commercial blue LED while I was at university. I bought one for £20 and we all sat looking at this clear 5mm package in a darkened room as we ramped up the current. It absorbed us for most of the evening.

Indeed. A company I worked for had a top end audio panel that used them but the manufacturing spread was massive from turquoise to royal blue. They had to be selected by eye to get sets that were the same colour and the ones at the fringes were discarded. I ended up with a very early set of blue Christmas tree lights. If the LEDs had been bought it would have cost several hundred pounds. One thing I discovered though was a high failure rate when they were pulsed. In the end I stuck to a constant voltage and they are still going strong
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Old 25th Jan 2019, 8:13 pm   #6
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Default Re: Early LEDs

First LED I had to play with was a red TIL209 Texas Instruments one, bought from the DORAM catalog in the mid-1970s.

I was really expensive so I was nervous about powering it up the first time in case I got it wrong and killed it.

A couple of years I was designing process-control gear using the Monsanto MAN-3A 7-seg LEDs driven by 7400-series TTL.
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Old 26th Jan 2019, 12:33 am   #7
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Default Re: Early LEDs

I noticed that the displays appeared to be 7 segment green LEDs on the control panel in the lunar module while watching the film "Apollo 13" recently. That surprised me somewhat, but I assume that NASA had the funds available to pay for all the latest technology at that time. Or maybe the displays were already around in the USA. I don't recall the year but I assume it would be the early seventies. I don't remember seeing them in use till around 1980 when I was still at school and on limited funds. I couldn't afford one at the time. I think they used a 7447 to drive them.
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Old 26th Jan 2019, 1:11 am   #8
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Default Re: Early LEDs

I'm glad it's not just me who notices that sort of thing! I'd also wondered about the seemingly electro-luminescent style illumination of the module instruments, and suspected that they were both set-designer's license, so to speak. Of course, both might have been available at the time for the "moon-or-bust" sort of budget, but I'm sceptical.

Colin
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Old 26th Jan 2019, 1:39 am   #9
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Default Re: Early LEDs

My recollection is that the first LEDs we had at Plessey in the very early 1970's cost around £2 each, red only. By late 1974 the price had dropped significantly, and yellow and green ones were also available, but not blue. Extract from the RS catalogue for Dec 1974-March 1975 attached. Much the same range was available in 1976, but by 1980 a range of numerical displays, both gas discharge and LED, including green, was available.They would have been available in the US at an earlier date. No blue LEDs were listed
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File Type: pdf RS opto 1980.pdf (863.0 KB, 101 views)

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Old 26th Jan 2019, 9:28 am   #10
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Default Re: Early LEDs

I had some sample LEDs in 1974, red, yellow and green. I can't remember who supplied them. I found that if the green LED was operated at very low current its output it was more like a yellow LED. I first saw a blue LED in 1997 but it didn't appear to be very bright.

At university we had red LED which didn't appear to work very well it needed a large current to get any output but failed shortly afterwards.

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Old 26th Jan 2019, 10:43 am   #11
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Default Re: Early LEDs

I recall being shown a blue 5mm LED quite early on, and being told they were £20? £30? each, the higher figure wouldn't surprise me as the intermediary involved at that time had we procured one was not whiter than white.

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Old 26th Jan 2019, 10:46 am   #12
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Default Re: Early LEDs

A friend of mine had a VW Golf many years ago (possibly a MkI) which seemed to have LEDs for the dashboard warning lights, including a blue LED for the main beam warning. At the time, blue LEDs were several pounds each ( the cheap chemistry for them hadn’t been invented) so we were sceptical, but all the lights seemed to be LEDs.

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Old 26th Jan 2019, 11:05 am   #13
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Default Re: Early LEDs

Definitely- i saw a VW of that era and drew the same conclusion.
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Old 26th Jan 2019, 7:10 pm   #14
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Default Re: Early LEDs

Quote:
Originally Posted by Biggles View Post
I noticed that the displays appeared to be 7 segment green LEDs on the control panel in the lunar module while watching the film "Apollo 13" recently.
The Apollo guidance computer (AGC) Display and Keyboard Unit (DSKY) used seven segment and +/- electroluminescent lights operating at 250 V 800 Hz. The DSKY had 120 latching relays and 12 nonlatching relays, most of which drove the electroluminescent lights.

High voltage electroluminescent display of this type was a short lived technology that was soon superseded.

More information here:
https://www.ibiblio.org/apollo/hrst/archive/1029.pdf

David
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Old 26th Jan 2019, 7:25 pm   #15
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Default Re: Early LEDs

Quote:
A friend of mine had a VW Golf many years ago (possibly a MkI) which seemed to have LEDs for the dashboard warning lights, including a blue LED for the main beam warning. At the time, blue LEDs were several pounds each ( the cheap chemistry for them hadn’t been invented) so we were sceptical, but all the lights seemed to be LEDs.
I had a 1985 VW Jetta the dashboard indicators were LEDs except the main beam warning, this was an incandescent bulb with a blue covering, I currently have a 1996 VW T4 and the high beam warning light on this also appears to be a conventional bulb.

Dave

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Old 26th Jan 2019, 8:22 pm   #16
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Default Re: Early LEDs

Quote:
Originally Posted by turretslug View Post
I'm glad it's not just me who notices that sort of thing! I'd also wondered about the seemingly electro-luminescent style illumination of the module instruments, and suspected that they were both set-designer's license, so to speak. Of course, both might have been available at the time for the "moon-or-bust" sort of budget, but I'm sceptical.
I think the instrumentation (and possibly the seven segment displays) used electro-luminiscent panels. Fran Blanche has some youtube material on that.
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Old 26th Jan 2019, 8:39 pm   #17
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Quote:
Originally Posted by G6Tanuki View Post
First LED I had to play with was a red TIL209 Texas Instruments one
Mine too, I reckon 1977. Not very bright but did the job - for a 'Soil Moisture Indicator' project featured in Everyday Electronics.

By 1978 I was using red LED's as panel indicators. Price was coming down at around 12p each.

The first blue one I saw for sale was from Electrovalue, £27 each and they had "(Really!!)" after the price. I'd have put this late 1980's but I don't have a life event to date it against.
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Old 26th Jan 2019, 9:37 pm   #18
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Default Re: Early LEDs

The Grundig CUC220/720 etc series colour TVs from 1980 had green 7 segment displays , so I guess mainstream by them.
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Old 26th Jan 2019, 9:41 pm   #19
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Default Re: Early LEDs

Thanks very much, David, for posting the link to the most interesting Apollo document (#14): I had never heard of "rope memory" before. I couldn't see any mention of the colour of the electro-luminescent display. The 7 segment gas discharge display of the 1980 RS catalogue (#9), was driven by much the same voltage, and produced orange light. [No personal experience.]

Also interesting to note that, in the foreword (page iii), the expression "Quantum Leap" is used in the sense of a great advance, the opposite to its meaning in Physics of the smallest possible change. I had thought its arguably inappropriate usage had its origin in that TV series where the guy becomes various men (and occasionally women) in the past and puts right things that had gone wrong, but here it is used in this way in 1972.
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Old 26th Jan 2019, 9:54 pm   #20
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Default Re: Early LEDs

I acquired a few ex-equipment Monsanto MV10B's from a project assignment whilst on a college-based placement to M*r*n* Research Labs back in '74; they're still in my 'useful optoelectronics' drawer here
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