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'[EE]:Optrex LCD backlight and driving'
2000\08\29@023256 by Quentin

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I've got a batch of Optrex LCD's DMC16230 NYJ-LY-D. The variant code is
different from the LCD I've been using for development. That code is
NY-LY-B. Nowhere on the 3 Optrex web pages can I find a list explaining
the variants. And my emails remain unanswered.
I know that this tells me something about the backlight and the display
characteristics. Anybody got a list that explains it? Here is my
problems:
On the new batch, I had to drive Vee to about -2.5V to get the display
to show something. My development LCD worked OK at 0V. I only got a
positive 9V available for this project. How do I generate this -2.5V
(variable)?
(Don't ask me how much I was swearing when I did the first prototype,
hehe)

Do I need an inverter for the backlight?. Or do somebody have a simple
circuit to drive the backlight?

Thanks
Quentin

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2000\08\29@080505 by Bob Ammerman

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If you have a pin or two free you can create a charge pump using the PIC
(you do have one in there don't you? :-) ) to pulse them.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\08\29@094622 by Nicholas Irias

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The NY(nil)J-(nil)LY-D means:

N: LCD type is STN
Y: Back color is yellow
nil: means 6:00 viewing angle
   ( 'U' means 12:00, 'L' means 9:00, 'R' means 3:00)

'J': per a footnote in the Optrex databook, this means
   'Improved response time on Low Temperature operation with Dual power
supply'

nil: means display mode is reflective, transmissive with Backlight
L: means backlight is LED
  ('EL' means electoluminescent, and nil means no backlight)
Y: means backlight color is yellow

B vs D: this code is not in my Optrex data book.  My guess is that this
letter code is a hardware rev code.

The bad news about the 'J':
The special cold weather version of the LCD has changed the practical Vee
voltage range.  The databook power supply example for the extended temp
model shows Vee going to a pot that is a divider ranging from 0v to -7v.  On
the standard temp model, that divider ranges from 0v to +5v.

If you can return the LCDs and get the standard temp model, that is the
thing to do.  Unless you got these surplus, you probably paid extra for the
'J' option that is creating your dual power supply requirement.

Regarding the LED hookup:
The LED for this model has a 4v forward voltage, at a max of 300mA.  The way
I read the book, there is no internal dropping resistor so you are
responsible for limiting the current with a dropping resistor of you own.


{Original Message removed}

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