Re: need a new lcd display

"PolyVinalDistillate" <PolyVinalDistillate@xxxxxxxxxxx> wrote in message
news:1165542608.562811.65260@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I've had another look over your datasheet, and it's a little cryptic in
places and lacking good information to answer little riddles easily :)

your not bloody kidding lol !!!!
I think its disgracefull to not put enough information at least somewhere on
their site,
I gues an email to them is in order.

I've never encountered the 'M Modulation' block in any panels I've
looked at... There are two lines going into it though, and it makes me
wonder if the M line needs a different waveform to what I'm used to. I
assume it would be CL1 and M that supplied the modulation circuit, in
which case it's possible the display arranges to 'paint' each line in
an alternating voltage... You could try odd duty cycles on the M input
and see what happens. But it may be arranged to take the normal,
equal-duty M signal and generate alternating line scans from it. If the
image appears and then fades out, then the liquid crystals are getting
a DC drive, and are likely to be damaged (but hopefully still useable).
I'd also suggest something more interesting than a chequorboard - I've
had displays work fine with that, but turn out to be drawing stuff on
the screen in a really bizzare way :)

If I understand it and from experience of the last panel the ac signal is
just to stop damage from long term DC votage and should still see something,
unless its also used to actualy draw the line or something.
if it cant even display the chequorboard I doubt it wil display much else
either.
(nor will it be an great deal of use lol)

When the scan stops the line stays there and gradualy fades out.
im not sure ive got the correct dc power up sequence,
some data sheets are rather picky about how vee,vdd,von etc are brought up,
although vee is generated from vdd so it cant come up for a short while.

ive just found a few other data sheets wich give the timings, and have the
same name for the signals :-
http://homepages.nildram.co.uk/~displaze/PDF/LCD/Arima/MC57T01E.pdf
http://www.electronic-engineering.ch/microchip/datasheets/lcd/lcdprinciples.pdf
FLM stands for first line marker wich is nice to know.
not sure what M could stand for.

PS ive just found the data sheet on one of the chips inside the panel so
that shoud shed some light,
lc4901,lc4930
http://www.datasheets.org.uk/datasheet.php?article=1986855
although it doesnt seem to tell me anything new.
at least I can probe a few of the pins.

Also, I'm not sure from the datasheet of the contrast voltage range
(I'm tired and might not be thinking right). It looks to me like the
Vop column in the voltage specifications must refer to to the Vo
voltages for nice contrast at various temp. ranges, in which case
contrast would be negative. It's been a while since I hooked up one of
my panels, and I have a suspicion at least one was a negative Vo too,
but driving it negative always makes me nervous! I'm sure I've blown a
panel by giving it -ve Vo before... Have you been testing it from 5v to
0v, or 5v to -25v ?

Ive tried 0-5v as that seems to be common on other data sheets ive seen,
im a bit nervous that negative voltage might blow it up too !
maybe I might try makeing it negative -5v through a 1Mr or something.
however it is more visible at 0v than 5v.

Final plan, another risky one... raise the Vee (or rather lower) to -30
to -35 (not over the spec. 'MAX'). I say risky, as it's the highest
contrast voltage I've heard of yet, but the datasheet appears to
suggest it's possible. Also, my panels are really old, and all pulled
from ancient XT "laptops", so perhaps yours requires a higher drive
voltage than did mine. Bear in mind I'm guessing at possible solutions,
one of which *could* damage the liquid crystals, and two of which
*could* damage the control ICs. I'd be tempted to try in your shoes
with two panels to play with- but dissapointed to be reduced to only
one!

Ive gone to about -27, wich if I understand it coresponds to a vop of 32
actually disconecting the -vee mad no diference at all,
its as if its not even using it I might trace the signal on the panel,
its not taking hardly any current at all either.

worse thing is if I destroy both of them, I dont want to plug the other one
in and find its the same,
then I wont know if ive got 2 panels wich I dont know how to use or 2 dead
ones.
although its new theres a chance it may be dead for one reason or another.


Good luck - hope it doesn't end in smoke!
Nick.

thanks and thanks for the help so far,
Colin =^.^=



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