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'EL backlight drivers?'
2009\04\15@055806 by Roger Weichert

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Hi all  ...  I am repairing some gear which uses LM24014 LCD (240 x 64) panels.

The equipment has never had a backlight, and the customer has requested that I source and fit an EL panel to illuminate the display.

I have obtained some LFOB08 EL panels, which suit the display, but am now looking for a suitable driver or invertor for them.

They could either be driven by 240v or a 5v or 12v supply off the existing board . depending on the current draw.

Something ready made .. off the shelf, here in Australia, would be great.

Thanks, Roger

2009\04\15@072456 by Russell McMahon

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> Hi all  ...  I am repairing some gear which uses LM24014 LCD (240 x 64)
> panels.
> The equipment has never had a backlight, and the customer has requested
> that I source and fit an EL panel to illuminate the display.
>
> I have obtained some LFOB08 EL panels, which suit the display, but am now
> looking for a suitable driver or invertor for them.
> They could either be driven by 240v or a 5v or 12v supply off the existing
> board . depending on the current draw.
> Something ready made .. off the shelf, here in Australia, would be great.

I'd recommend avoiding EL backlights if at all possible.
YMMV but I have had horrendous experiences with them. They have quite finite
lifetimes, are somewhat dependant for lifetime on waveforms and voltages
from the driver and they seem to do nasty things load wise as they age. The
ones we used were not overly cheap compared to eg LED units. At one stage I
supported a significant number of units which used them for a large LCD
display, and the experiences with them were most offputting.

Modern LED backlights are able to offer superb results at modest power
levels. In some cases added LED front lights may do what you want.



Russell



2009\04\15@110143 by William \Chops\ Westfield

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On Apr 15, 2009, at 2:58 AM, Roger Weichert wrote:

> I have obtained some LFOB08 EL panels, which suit the display, but  
> am now looking for a suitable driver or invertor for them.
>
> They could either be driven by 240v or a 5v or 12v supply off the  
> existing board.

EL panels can typically (sometimes?) be driving straight of the AC  
line (50-60Hz, 100-250Vac), sometimes with a current limiting resistor  
at the higher voltage.  They're fundamentally capacitor-like in  
nature, so current consumption is low and self-limiting for a  
particular frequency.  (now, DC-based inverters will run 400+ Hz that  
gives higher brightness at lower voltages, but if you HAVE AC, that  
may be all you need.)  Your panel vendor should have relevant advice  
(my experience is with the EL-wire, which does have specific  
recommendations for direct 110V and 240V AC drive...)

BillW

2009\04\16@135914 by Clint Sharp

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In message <B55EC7B1EEC14BA3836E224A6F1DCC70@gaddiel>, Russell McMahon
<spam_OUTapptechTakeThisOuTspamparadise.net.nz> writes
>At one stage I
>supported a significant number of units which used them for a large LCD
>display, and the experiences with them were most offputting.
I used to support some too, definitely less reliable than LED but I can
only remember one particular type of EL causing *lots* of problems but
for sure, they all dim and change characteristics with age. If the
connect points aren't sealed properly or are overheated then they can
fail fairly quickly due to moisture ingress.

The inverters can also be fun but not because they fail ;-)

 I'd expect a good few years operation from an EL panel, I still have
some that are over ten years old that work fine although I wouldn't care
to say how much they have dimmed/changed colour purely because the
change is so gradual.
>
>Modern LED backlights are able to offer superb results at modest power
>levels. In some cases added LED front lights may do what you want.
LED backlights may not always work for retrofitting though, unless the
display and backlight were intended for each other and designed as such
it can be difficult to get even illumination, it's not always possible
to get a LED backlight to fit, I've not seen many LCDs that you couldn't
slide an EL panel underneath.
>
>
>
> Russell
>
>
>

--
Clint Sharp

2009\04\16@144433 by Vitaliy

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Russell McMahon wrote:
{Quote hidden}

I don't know... my experience is that LED backlights are many times as
power-hungry as comparable EL lights.

Vitaliy

2009\04\17@004133 by William \Chops\ Westfield

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On Apr 16, 2009, at 11:43 AM, Vitaliy wrote:

>> Modern LED backlights are able to offer superb results at modest  
>> power levels. In some cases added LED front lights may do what you  
>> want.
>
> I don't know... my experience is that LED backlights are many times  
> as power-hungry as comparable EL lights.


Power, or just current?  EL backlights may only consume a few mA  
compare to LED's 100-odd, but that's at 100+Vac, so the watts can add  
up (plus you have converter losses.)

BillW

2009\04\18@034732 by Russell McMahon

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>>> Modern LED backlights are able to offer superb results at modest
>>> power levels. In some cases added LED front lights may do what you
>>> want.

>> I don't know... my experience is that LED backlights are many times
>> as power-hungry as comparable EL lights.

> Power, or just current?  EL backlights may only consume a few mA
> compare to LED's 100-odd, but that's at 100+Vac, so the watts can add
> up (plus you have converter losses.)

This reference suggests that El efficincy is about 3 to 5 l/W
http://www.edn.com/article/CA56670.html
(Their comment about LED effo\icncy is wrong, so ...)

Getting 90+ l/W from an LED is easy enough nowadays. Above CFL efficiency
and approaching that of a straight fluorescent tube.
There are commercially available LEDs at 130+ l/W.(So bright !!!!!!!!!)

If El had high efficincy it would probably be being used in more mainstream
lighting applications..

A typical modern monitor output is 300 l/M^2.
Area of a 20" monitor is about 0.15 m^2 (E&OE) so lumens = 300*.15 = 45
lumens or about 500 mW of LED lighting equivalent.
>From dimming memory. even a bright EL display is very much downn that
brightness level. Power consumption would be some Watts, but that is
partially due to the inverter efficincy.


 Russell





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