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Subject: Re: LCD Question
Date: Sat, 02 Nov 2002 02:37:43 -0800
X-Mailer: Mozilla 4.78 [en] (Win98; U)
References: <firstname.lastname@example.org> <email@example.com> <3DC3A6B5.B6A36B8B@spray.se>
> Have you tried to search for the data sheet on the web? Any pdf can be found
> outthere nowdays...
> If there is a large black circuit near the connection to the display...search
> for that number...
> Or connect a 10 kohm resistor to a +5 Volt (or a segment nearby) on the PCB and
> try to find the connection.
> "Jack B. Pollack" wrote:
> > Thanks Wafer & Gary ,
> > Both of your posts were helpful. From Wafer's post I envisioned the whole
> > process as a data and address type of scenario for each digit, but was
> > baffled when I masked out with tape one of the contacts to find what
> > appeared to be random segments disabled.
> > Gary's post was right on the money 'it is not even on a digit basis'.
> > Now that I understand how this works let me try to ask a little more
> > specific question:
> > We have a really nice Jacob Jensen digital clock that only displays time in
> > 24 hour format, this drives my wife crazy. When I opened the clock I found
> > a hardwired jumper to set the time format.
> > The clock now displays time in 12 hour format, but the display lacks a PM
> > indicator making the alarm function useless.
> > I am sure that the 'blob' is outputting a signal for PM, but how do I find
> > it (In a data/address scenario I would have looked for it on the 'digit'
> > with the other indicators ('Alarm on', time set, etc)? But since segments
> > are 'random' how do I find it?
> > Secondly, I was going to drive a small low current LED for the PM indicator.
> > I dont think this will work based on the explanation of the 2 square waves.
> > I guess I could NAND them and then use the NAND as a driver for the LED (I
> > dont know if the square wave voltage is too low to drive TTL). Any
> > suggestions on indicate PM would be appreciated.
> > Thanks again
> > "Jack B. Pollack" wrote in message
> > news:firstname.lastname@example.org...
> > > I have several questions about a LCD display in a portable clock that I
> > > have:
> > >
> > > 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
> > > addressed?
> > >
> > > 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.
> > >
Electroluminescent. Make sure the DC offset of your drive is ZERO POINT ZERO
volts. Very little offset can dramatically reduce the life of the backlight.
> > > Any insight would be appreciated.
> > >
> > > Thanks
> > >
> > >
> > >
Bunch of stuff For Sale and Wanted at the link below.
Tek 2465, TFT projector, ham radio, 30pS pulser
Tektronix Concept Books...
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