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Old 7th November 2007, 11:59 AM   #1
Unkle77 is offline Unkle77  England
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Default Replacing an old LCD display

I am replacing an old back lit 16x2 LCD with a new one but there is a problem, the old one has 14 connectors and the new one has 16.

Unfortunately i can not find a spec sheet for the old one, so the question is:

Of the 16 connectors on the new one is there any which are not strictly needed?

Here is a link to the spec sheet of the new LCD:
http://www.maplin.co.uk/Media/PDFs/N27AZ.pdf

The 14 connectors on the old LCD come from a chip on the main board, these then connect to the controller but i can not work out what 1-12 do but i know 13 and 14 are for the back light.
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Old 7th November 2007, 10:55 PM   #2
BWRX is offline BWRX  United States
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You need to know the pin out of the old LCD in order to know for sure if the new one will work in its place.
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Old 8th November 2007, 05:07 AM   #3
Nordic is offline Nordic  South Africa
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the 2 extra pins are for the LED backlight... you don't HAVE to connect them on many models...
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Old 8th November 2007, 08:45 AM   #4
Unkle77 is offline Unkle77  England
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Quote:
Originally posted by BWRX
You need to know the pin out of the old LCD in order to know for sure if the new one will work in its place.
if i connect them in any order will i kill the LCD? or will it just not work until i find the right combination?

Quote:
Originally posted by Nordic
the 2 extra pins are for the LED backlight... you don't HAVE to connect them on many models...
The 14 connectors on the old one includes the 2 led back light connectors so essentially, it only has 12 connectors to transfer data.
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Old 8th November 2007, 11:27 AM   #5
Nordic is offline Nordic  South Africa
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Pin 1 on the LCD is normaly marked... if you can find the marks on the two LCDs swap them out, so that pin 1 matches...
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Old 8th November 2007, 12:54 PM   #6
Unkle77 is offline Unkle77  England
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Quote:
Originally posted by Nordic
Pin 1 on the LCD is normaly marked... if you can find the marks on the two LCDs swap them out, so that pin 1 matches...
So are you saying the the pin layout on a LCD is universal?
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Old 8th November 2007, 11:28 PM   #7
dangus is offline dangus  Canada
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The 14 pins are pretty standard, although they can be arranged in single inline or dual inline. Things like backlighting and contrast vary from one model to another. Certain displays need a negative polarity on the contrast (usually only extended temperature range versions), and with backlighting, some displays need a series resistor to limit current, while others run directly off 5V. And some use EL (electroluminescent) backlighting which requires an AC drive voltage.
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Old 20th November 2007, 09:13 AM   #8
Unkle77 is offline Unkle77  England
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hmmmm, it didnt work, i spent a lot of tiem working on this and actually worked out quite a lot on how lcds work.

the new lcd with 14 lines plus 2 for the led work with 4-bit or 8-bit data, hence the ability to use just 10 of them or all 14 lines.

with my old one i have decided it uses 6-bit data though i can not find anything on the internet which would support this......

so basically nothing worked, not even the leds, i could not get it to work with any logical combination and i am not sure if i have done any irreversible damage to the control chip on the main board and i can not check as i managed to fry the conductive strip on the old lcd with my soldering iron..........

so im now playing the waiting game to either find a cheap broken box on ebay or get bored and fork out lots of money and get a new one from the origional manufacture and hope it all still works.
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Old 20th November 2007, 10:03 AM   #9
Nordic is offline Nordic  South Africa
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send me a message useing the email button, so I can send you some LCD tutorials... very nice one that teaches you how to start up an lcd with just switches even... then you can test the LCD seperately...
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Old 20th November 2007, 04:35 PM   #10
Nordic is offline Nordic  South Africa
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PDFs sent.
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