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 Post subject: Electroluminescent panel lighting
PostPosted: Jul Mon 15, 2019 8:51 pm 
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I have an electroluminescent panel in a Sylvania RM-300X radio.

It never lit very bright, but I don't know how bright it really should be as I have nothing to compare it to.

I originally disconnected it since It served no real purpose given its dimness.

When I converted the radio to use an external AC transformer I lost the ability to power the panel.

What I need is a small circuit that can run on 22.5Vrms or 29Vdc that will produce 120Vrms at 60Hz.

Ideally a small transformer would work if I can find one very small, but if not that then I'll have to use a circuit.

I am not sure what current the panel draws, but I can test that tomorrow.

The dial face is clear plastic with the numbers raised from the plastic and painted with chrome paint so they would be easily seen in normal room lighting. That makes me think the panel may have been only to light the dial at night and thusfore may not be as bright as one would think it should be.

Now if it is indeed determined that the panel is actually bad maybe this one can be cut to fit.

https://www.adafruit.com/product/414


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Mon 15, 2019 11:05 pm 
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Are you sure the EL panel runs at 115V?

Most of the ELs I've seen in test equipment run at less than 25VAC. You can increase the frequency some (I used an AC standard...) and see the brightness at various voltages and frequencies.

I've got several loose ones from old Telecom stuff - the voltages are all 12-18VAC, but the panels are only a few square inches in area - backlightsfor a menu-based LCD screen.

Edit: I see my ELs are the exception, not the rule....

https://www.allelectronics.com/category ... ips/1.html

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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Mon 15, 2019 11:38 pm 
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I may experiment with the panel tomorrow.

As I have no reference I have no way of knowing how bright the panel actually should be.

The panel at 120Vrms 60Hz draws 840uA.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Tue 16, 2019 5:30 pm 
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Most EL panels need more than 60 VAC. Driving with a higher frequency will get more light out with the same voltage.

The one in the link is also "high" voltage.

Maybe you would like this boost converter: https://www.adafruit.com/product/564

Be aware if used with a radio or audio amp, you might get some RFI or noise.

Rich


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Tue 16, 2019 6:15 pm 
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I built at ~60 Hz inverter out of a 12 V power transformer. It uses a couple of power resistors and capacitors. If you have a 25.2 V CT transformer on hand and want to try this, it could be just the ticket. Let me know and I'll snap a picture out of the book.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Tue 16, 2019 8:43 pm 
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I have an EL night light in the hall that has been plugged in up for years and by now a lightning bug can outshine it. I got a wingtip EL panel from a fighter jet(formation light) and made a night light out of that years ago. Very small amount of use since the 80s, this spring it still shone OK but not terribly bright. They were originally made to run off 400, instead of 60 cycles 115V. It is good enough in the dark to get your bearings if not illuminate much. In equipment that uses them and they fade out, I would consider an alternative device such as a piece of white translucent plastic cut to the same size and illuminated with LEDs of your choice, to avoid the power issues.

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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Tue 16, 2019 10:47 pm 
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I would need the same exact blue/green color though as I'm quite picky about colors.

It could be that mine is about done for.

Won't know unless there is someone experienced with the RM-300X radio and knows how bright the panel should be.

I'd definitely be interested in that circuit.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 12:16 am 
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Tube Radio wrote:
I'd definitely be interested in that circuit.


Here it is. Note that you won't need the two caps and coil in the output filter. Mine was made of a Radio Shack transformer that was not quite resonant at 60 Hz, but it lights up a regular 40 watt incandescent bulb and powered a 120 volt tuner I adapted to my car. The resistors get pretty warm. There are better designs out there, but this should be good enough for proof of concept. A better design would be to employ feedback windings in a transformer, which would run cooler than these power resistors.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 12:22 am 
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Most consumer EL panels used Zinc Sulfide as the phosphor. They weren't hermetically sealed, so over time the ZnS oxidizes or combines with moisture and becomes less active.

Rich


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 12:41 am 
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When I had mine lit I did notice some small dark spots so perhaps that is my issue.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 12:51 am 
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I have seen a few of those sets at around 10-15 years of use and the panel is really dim by then. The brightest one I recall having seen was good enough in a darkened room that you could clearly make out the numbers against the pale green background.

An aunt had a bunch of Sylvania electroluminescent flat night lights which were sold around the same time that radio was, and they kept getting dimmer and dimmer and dimmer. Of course those were intended to be left plugged in 24-7 just like the clock radio was. By the time they were 15 years old, they were useless, barely glowed.

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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 1:59 am 
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Thanks for the insight on the panels.

I'll go ahead and order the one I linked to.

That said is there any other way to get the exact bluish/greenish glow with something that lasts much longer?

Do you remember what color the tuning meter should light?

Mine is a lighter blue almost like a faded blue. The best way I can describe it is how some marantz receivers look which still use the bulbs without replacing the vellum paper.

I did see around the edge of the meter at the top some clear blue plastic.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 5:11 am 
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Tube Radio wrote:
Thanks for the insight on the panels.

I'll go ahead and order the one I linked to.

That said is there any other way to get the exact bluish/greenish glow with something that lasts much longer?


Here's one way: Cover the new EL panel with an acrylic filter that you make yourself. Craft stores have a liquid based colorant sold as stained glass paint. If the new blue EL panel is quite bright, start with some emerald green. Cut to size a piece of 1/8" acrylic you can get free from the trash can of a framing store. Clean the acrylic with alcohol and cover one side completely with tape. Make a tray out of heavy aluminum foil, put in just enough paint to cover the acrylic, dip the acrylic, bring it out so most of the paint runs off. Set it, tape down, on a completely level surface to dry. Remove the tape and check the color with the acrylic against the new EL material. You can add more layers, but if it's too green, you'll need a lighter green. Depending on how blue the EL is, the job may require yellow paint.

Never mind. Don't start there. The blue EL panel may be monochromatic and the green filter may not work. If you can find a white panel, filtering will work for sure. For that matter, you can try alcohol ink. It forms very thin color layers on acrylic. If you use white acrylic, that will help even things out.

Ok, on further testing, I put a blue LED inside a green cup and was able to approximate the blue green of an old EL night light. See photos below. So maybe that blue EL panel can be filtered.


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Last edited by Macrohenry on Jul Wed 17, 2019 6:28 am, edited 3 times in total.
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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 5:35 am 
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Location: pensacola fl
Hi ALL. The el panels were and still are used in audio processing equipment as part of the gain control element of compressor/limiters such as the teletronix/ urei la2 wich was the first to do so. They were used with cds cells in a light tight enclosure as a varaible resistor for gain control without adding distortion.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 6:37 am 
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Also there are some blue-green LEDs that have that EL look. http://ledmuseum.net/ledtur.htm

The trick is getting them to illuminate a panel evenly. Some have had success putting a row around the edge of frosted acrylic. That's a lot of LEDs though. Does anyone know how the LCD/LED monitors that use a white panel do it?

Here's the spectrum you're looking for, followed by the spectrum of that turquoise LED.


Image

From http://ledmuseum.net/ledtur.htm:


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 11:49 am 
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The shade looks close enough to where it may work.

I may look around at other panels to see if I can find an exact shade.

That said maybe I can find an edge lit panel like the type used for some LED backlighting that is the right shade.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 5:27 pm 
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Here you go, it's cuttable. It looks green unpowered, blue-green when powered.

https://www.amazon.com/USB-Inverter-10x ... SAZZ792BMB

What are the dimensions of the existing panel?


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Wed 17, 2019 6:43 pm 
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I like it but it is only good for 8000 hours.


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Thu 18, 2019 1:03 am 
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Acrylite Endlighten is a clear material when unlit, but has tiny particles that catch edge-lit light and reflect it evenly outward. Either use white LEDs and use a colored filter or use blue-green LEDs. They don't need to be spaced close together, as in this demo. He used RGB LEDs that can be tuned to just about any color. Your desire color appears 10 seconds in.

https://www.youtube.com/watch?reload=9&v=evGALmP4F8s


Just for the fun of it, I think I'm going to order a $2.95 sample that's 3" x 3"

Two questions:

What are the dimensions of your existing panel?
Is there room above or below it to make a wider panel so the brighter edges can be masked?


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 Post subject: Re: Electroluminescent panel lighting
PostPosted: Jul Thu 18, 2019 2:47 am 
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I can maybe take measurements tomorrow and post them here.


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