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'[EE]: Electroluminescent wire...'
2001\03\15@121917 by Bill Westfield

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[I knew I forgot something.  Repeating with proper [ee] tag...]


Speaking of switching regulators...

Have you seen this EL wire stuff?  It's pretty neat!
       http://www.playafish.com/coolneon

It's got some problems though, in terms of driving it.  It wants about
110V RMS (~300V P-P) at 2kHz or so for reasonable brightness.  All the
itty-bitty tiny EL driver circuits produce about 80V P-P @ 400Hz, which
just isn't enough.  So I'm thinking of building my own driver circuit.

This is where the PIC (or whatever) comes in.  If you read the datasheets
for EL drivers carefully, they're pretty trivial, and look like the sort of
thing that a microprocessor could control pretty easilly.  They have a pulse
circuit driving a coil that produces a "moderate" voltage (40VDC) and then a
switching circuit that drives this to alternating ends of the EL panel
(standard LCD-style voltage doubler) at the "desired" frequency.  I can do
that in a PIC, maybe, and I'll have a lot more control over the variables...

Except that I don't understand E&M very well, being a digital and SW sort
of guy...  What sort of voltage limit is there to the single-inductor boost
circuit, and what causes those limits, for instance...  I don't understand
how the inductor value comes into play (EL circuits accept a wide range of
inductor values.)  When do I give up and just wind a transformer, and can
I get variable voltages out of a transformer as well, or is it confined to
the turns ratios?  What about those royer converter things used for CCFL
drivers - are they applicable to lower output voltages?

Hints greatly appreciated...

BillW

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2001\03\15@125244 by Scott Dattalo

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On Thu, 15 Mar 2001, William Chops Westfield wrote:

> Speaking of switching regulators...
>
> Have you seen this EL wire stuff?  It's pretty neat!
>         http://www.playafish.com/coolneon

I didn't see any pictures...

> It's got some problems though, in terms of driving it.  It wants about
> 110V RMS (~300V P-P) at 2kHz or so for reasonable brightness.  All the
> itty-bitty tiny EL driver circuits produce about 80V P-P @ 400Hz, which
> just isn't enough.  So I'm thinking of building my own driver circuit.

Have you looked at Supertex, Durel, or Sipex? I haven't run across a 300Vpp,
2kHz driver, but there are many that will produce 200Vpp and 400Hz.

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2001\03\15@130946 by Bob Blick

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> > Have you seen this EL wire stuff?  It's pretty neat!
> >         http://www.playafish.com/coolneon
> > It's got some problems though, in terms of driving it.  It wants about
> > 110V RMS (~300V P-P) at 2kHz or so for reasonable brightness.  All the

Most EL I have used is quite happy with 60Hz, so you can plug it in the
wall(with a series resistor to limit the current, chosen by
experimentation).

Cheers,

Bob

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2001\03\15@173333 by Bill Westfield

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>> [no pictures at playfish.com]

Click on the "gallery" button at the top of the page.


>> EL I have used is quite happy with 60Hz, you can plug it in the wall

Oh, it's HAPPY with 60Hz, it's just not very bright.  Fine perhaps for
backlighting a watch in the dark, but not so good for halloween costumes at
dusk, model rockets at a distance, "accessories" in room lighting, fancy
front panels or architectural highlighting.  The inverters offered by the
manufacturer START at 400-600Hz and run as high as 10kHz.


>> [durel, sipex, supertex]

I know about them.  I got some very nice help from Toko in the form of a
modified evauation board with multiple inductors, and dissappointing results
have made me hesitant to persue other vendors with (superficially?) similar
products.  Maybe I should be more agressive...

BillW

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2001\03\15@180049 by Chris Carr

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> >> EL I have used is quite happy with 60Hz, you can plug it in the wall
>
> Oh, it's HAPPY with 60Hz, it's just not very bright.  Fine perhaps for
> backlighting a watch in the dark, but not so good for halloween costumes
at
> dusk, model rockets at a distance, "accessories" in room lighting, fancy
> front panels or architectural highlighting.  The inverters offered by the
> manufacturer START at 400-600Hz and run as high as 10kHz.
>
Pacel whose products are in the Farnell Catalogue seem to use around 1-2kHz
for their electroluminescent panels. Although they do indicate that for
aircraft applications, powering of 400Hz is acceptable. Their web site does
not have any information on their wire but it appears that a drive of 22mA/m
@ 12 volts into the inverter gives 100mCd/m2 light output. Somewhere we have
a 1m length with the matching inverter, will have a look and see if I can
find it and measure the inverter output.

http://www.pacel.co.uk

Regards
Chris

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2001\03\15@191528 by Ashley Roll

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Hi,

A friend of mine has a kit containing a bunch of the different colour wires
and some different drivers. I can't remember where he got it, but I can find
out if anyone wants to know.

I "reverse engineered" one of the drivers.. Cheap, dirty (don't run it near
a radio) but simple. Looking through my notes, I think it produced about
120v (I seem to remember getting that number from the data sheet that came
with the stuff.) And it was audible so 5KHz-10KHz maybe.. It did have a
clever flash circuit that only added 3 resistors and a cap..

The Inverter was just a simple single transistor driving a small
transformer. It ran from a pair of AA cells. If anyone is interested, I'll
draw it up and put it on a web site.

Cheers,
Ash.

> {Original Message removed}

2001\03\15@191734 by Bob Blick

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> Oh, it's HAPPY with 60Hz, it's just not very bright.  Fine perhaps for
> backlighting a watch in the dark, but not so good for halloween costumes at
> dusk, model rockets at a distance, "accessories" in room lighting, fancy
> front panels or architectural highlighting.  The inverters offered by the
> manufacturer START at 400-600Hz and run as high as 10kHz.

The how about taking the transformer out of an old PC power supply, take
its two transistors, put them on the 5 volt windings instead, crossconnect
base-collector with a couple of resistors, apply DC, and take output from
the winding that was formerly the primary? 6 parts total if you add an
input filter cap. Should probably oscillate at 50KHZ and make 100 to 300
volts with 12 volts applied.

Cheers,

Bob

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2001\03\15@193230 by Bill Westfield

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Perhaps I should have mentioned that I'd like to get this to be as small
and light as possible (thus the interest in the Watch-style EL drivers.)
There's plenty of inverter circuits that will WORK (as someone mentioned,
those provided by the manufacturer are pretty cheap and dirty) using
everything from power to audio to customer transformers.  I just want
something that occupies less than a square inch of PCB space, weighs 10g or
so, and does sequencing of multiple outputs (that's one of the reasons to
want to use the PIC to drive the voltage converter - there'll probably be
a micro in there to do the sequencing anyway...)

BillW

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2001\03\16@065503 by mike

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On Thu, 15 Mar 2001 16:33:10 PST, you wrote:

>Perhaps I should have mentioned that I'd like to get this to be as small
>and light as possible (thus the interest in the Watch-style EL drivers.)
>There's plenty of inverter circuits that will WORK (as someone mentioned,
>those provided by the manufacturer are pretty cheap and dirty) using
>everything from power to audio to customer transformers.  I just want
>something that occupies less than a square inch of PCB space, weighs 10g or
>so, and does sequencing of multiple outputs (that's one of the reasons to
>want to use the PIC to drive the voltage converter - there'll probably be
>a micro in there to do the sequencing anyway...)
The way I'd do this would be to use a dc-dc chip (e.g. MAX771) to
generate a HVDC supply using a simple inductor, then chop this at teh
EL drive frequency with a transistor full-bridge (several for
sequenced apps). This should be do-able in 1 sq.in.  The capacitance
of the EL should avoid the need for much capacitance on the output of
the DC/DC.

For sequencing several ELs, another approach might be to use a single
inverter and triacs to switch the output -I think you can get SOT-23
triacs (Philips or SGS-Thomson maybe?), you can certainly get them in
SOT-223 and TO-92. I used a large EL inverter with opto-triacs for the big clock I made
from pager EL backlight panels:
http://www.netcomuk.co.uk/~wwl/mikesclocks.html

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