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From: email@example.com (Bob Wilson)
Subject: Re: LCD Question
Date: Sat, 02 Nov 2002 04:41:14 -0000
Organization: Your Organization
X-Newsreader: WinVN 0.99.9 (Released Version) (x86 32bit)
In article <firstname.lastname@example.org>, N@NE.nothing says...
>I have several questions about a LCD display in a portable clock that I
>There are 13 'pad' connections on the PC board that connect the LCD display
>to the PCB and 'blob chip'. If I look at these connections with a scope
>there is a square wave on each of them.
>The display has no electronics in it, how is the data transferred to the
>display and decoded? How are the individual segments on the display
>The second question is about the LCD backlight:
>There is a thin film (looks like a piece of paper) with 2 contacts on it.
>When 50V AC is applied the film glows blue and backlights the LCD. I would
>like to find out more about this type of backlight technology and how to
>build a similar driver circuit for the backlight.
>Any insight would be appreciated.
It is as old as the hills. It is called an electroluminescent panel, or EL
for short. I recall when I was a kid, we had a trendy little telephone in
the early '60s that had an EL backlighted dial.
The EL panel you are referring to is available custom-designed from a large
number of vendors (mostly in the far east). I just finished designing a
custom one for a pager we are making, and earlier this week got die-cut
samples in a variety of colours (blue, green, white and orange) from our
The small panels you see are made using a screenprinting process, where the
various layers of phosphors and so on are deposited by screenprinting on a
thin plastic substrate.
The main problem with EL panels is their limited lifetime in constant use.
The technology is anything but new, so you will have no problem searching
under the keywords EL Panel, or Electroluminescent Panel.
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