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Old 18th Nov 2018, 8:18 pm   #1
avocollector
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Default Electroluminesence

Back in the early 60's a few years before led's appeared I recall reading an article in PE about electroluminesence - essentially you sandwiched a layer of something (granulated zinc sulphide??) between two electrically conductive pieces of glass (made so by depositing stannous fluoride as a vapour on them) applied an ac voltage (think it was 1 kv) and bingo you got light!! Has anyone seen any further developments over the years?? I recall wanting to experiment but as a child was dissuaded by the reactiveness of stannous fluoride, the need for high vacumn pump etc. The article mentioned this as a possible future lighting panel method.

I suspect once led's appeared, development on this was shelved which I think is a pity.
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Old 18th Nov 2018, 8:28 pm   #2
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Default Re: Electroluminesence

Electroluminescent panels (I'm not sure about the technology but they needed an inverter) were used as backlights in some of the first large LCD flat-panels; I remember seeing these in some 1980ish aviation instrumentation applications. They had a very distinctive green glow!
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Old 18th Nov 2018, 8:55 pm   #3
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Default Re: Electroluminesence

Didn’t HH amplifiers use electroluminescent panels to backlight the control legends?
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Old 18th Nov 2018, 9:00 pm   #4
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Default Re: Electroluminesence

Around the same time PE did an article on something like a tuner/amp with an electroluminescent-lit tuning scale on the case top. I think the panel came from an unlikely source... Saunders-Roe developments?

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Old 18th Nov 2018, 9:12 pm   #5
Paul JD
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Default Re: Electroluminesence

Quote:
Originally Posted by mole42uk View Post
Didn’t HH amplifiers use electroluminescent panels to backlight the control legends?
Yes, the HH IC100 had this (there may have been other models with it as well?). If I remember correctly they were pretty awful sounding guitar amps but looked cool!
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Old 18th Nov 2018, 9:16 pm   #6
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Default Re: Electroluminesence

Philips used EL glass panels in the early sixties for tuning scale illumination. They were connected across the mains or possibly to a similar voltage secundary winding. They arced and tracked after a relatively short time and were replaced with a service kit of conventional parts.

More recently (1990's I think) EL foils were sometimes used for backlight in LCD displays on CD players and the like. Also, some computer case modders liked to use them. Some suppliers may still have them, possibly Conrad.
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Old 19th Nov 2018, 2:45 am   #7
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Default Re: Electroluminesence

In the 70s I had electroluminesent spacers fitted behind a couple of bedroom light switches so you could locate them in the dark.
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Old 19th Nov 2018, 4:24 am   #8
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Default Re: Electroluminesence

The model railway hobby has (or had) miniature electroluminesent signs in recent years.

Seemed mainly confined to US advertisers, don't recall seeing anything in the UK press.
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Old 19th Nov 2018, 8:13 am   #9
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Default Re: Electroluminesence

I have a retail point of display item that is wrapped in a flexible electroluminescent material - see separate thread elsewhere. I guess the flexible product was subsequent to the glass one.
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Old 19th Nov 2018, 9:17 am   #10
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Default Re: Electroluminesence

In the US electroluminescent devices were common in the 1960s. It was developed by Sylvania and often called by its trade name, Panelescent. Probably its most common use was in small plug in night lights or light switch covers. Many Sylvania radios and TVs used panelescent panels, as did several Chrysler cars for their dashboard instrument lights.

Here is a magazine article from 1957 about the development of it: https://books.google.com/books?id=ii...201957&f=false
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Old 19th Nov 2018, 9:53 am   #11
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Default Re: Electroluminesence

Lexus use EL instruments too, with the rather dramatic effect of the panel 'appearing' from a black background when switched on.
EL materials are still widely advertised on eBay, and no doubt elsewhere.
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Old 19th Nov 2018, 9:59 am   #12
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Default Re: Electroluminesence

EL devices are actually pretty robust and, until recently at least, had the advantage that they could be very bright compared with competing display technologies. I believe that the combination of brightness and proven track record made them the technology of choice for displays in NASA's space shuttle. In a previous life I worked for a while with a UK research group among whose applications was development of a helmet-mounted head-up display for formula 1 drivers (the display had to be light in weight, so small, but bright enough to be very clearly visible in full sunshine).

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Old 19th Nov 2018, 11:34 am   #13
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Default Re: Electroluminesence

They are also used to backlight digital watch displays, and some alarm clocks too. One interesting item I have is a ‘One 4 All’ remote control in which the entire keypad is made up of a flat EL panel, where different functions appear on the keypad as lit up symbols. Certainly the most interesting use of EL I’ve ever seen!

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Old 19th Nov 2018, 12:00 pm   #14
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Default Re: Electroluminesence

My Casio watches (<£16, Argos) have EL backlighting- from 3 volts! I'm not sure if this version is still sold. Much better than the thinner and cheaper version, where the filament lamp can't shed an even light across the panel. I've not really contemplated the science behind it until now. If they made better (or replaceable) straps these watches would last and last.

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Old 19th Nov 2018, 12:23 pm   #15
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Default Re: Electroluminesence

The Casio watches make a high-frequency whine when the light is operated, presumably from a DC-DC converter.
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Old 19th Nov 2018, 12:24 pm   #16
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Default Re: Electroluminesence

..And the fact i can't hear that whine any more is down to me, not the watch!
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Old 19th Nov 2018, 1:06 pm   #17
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Default Re: Electroluminesence

The control panels in the Tornado aircraft cockpits used EL panels, powered by the aircraft 115v 400Hz supply, so used in the 70s. I think the panels glowed internally over their whole area, but only showed where the captions were engraved through the outer grey surface.
Despite having worked on the Eurofighter/Typhoon aircraft for 13 years I can't remember what technology that uses for control panel lighting!

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Old 19th Nov 2018, 1:40 pm   #18
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Default Re: Electroluminesence

Numerous vendors on ebay and elsewhere offer electroluminescent wire, a few mm in diameter. It consists of a wire core coated with the light emitting material, overlaid with a thin wire spiral and enclosed in transparent plastic.

It has many decorative uses, usually powered from dry cells via a miniature inverter.
"serious" uses are limited but include;
Attached to horse harness or blanket for night time visibility.
Dog collars ditto.
Fit around stairs and doorways for safe night time use.
In red to provide a good spread of very low level lighting that wont impair night vision. For example in military dormitories in case of sudden night action. Complete darkness carries risks of falling over or failing to locate vital kit, normal lighting ruins night vision.
In lifeboat houses for night launches.

Often called "neon wire" though it has no connection with neon.
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Old 19th Nov 2018, 3:02 pm   #19
avocollector
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Default Re: Electroluminesence

many thanks to everybody for these interesting leads on the subject.
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Old 19th Nov 2018, 3:11 pm   #20
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I used one to light the dial on my DAC90A, it's on this forum somewhere. Powered in parallel with the heater chain.
 
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