Identify the 16x2 lcd

Discussion in 'General Electronics Chat' started by aamirali, Sep 3, 2014.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    I have got one equipment & I have to replace its lcd with new one.

    Lcd which was earlier in equipment, I have taken its pics & attached.
    I had tried to replace it with standard 16x2 lcd but it didn't work.


    1. I had noticed that in this lcd pin 1 i.e vss & pin 16 were shorted internally via tracks & pin 2 i.e vcc was shorted to pin 15 i.e anode. There was no jumper wire, it was shorted via tracks.

    2. I replaced it with standard lcd with connections as in attached picture "3". But it is not working.
    Connection pins have solder on them.

    3. Also as in pin 1, there is different in background led white strip.

    4. When I replaced the lcd, nothing shown on it while this lcd works fine.

    Anyone knows what is this lcd.
     
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  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,073
    3,856
    Pins 1 and 2 power the hitachi-compatible LCD driver chip, pins 15 and 16 power the LED backlight (internal current limit so no resistor needed).
     
  3. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,504
    380
    hi,
    Your description is difficult to follow.?
    Are the character pixel blocks visible on the LCD.?
    Is there a Contrast pot on the main PCB.?

    The A/K connections are the LED back light .

    Look at this attached pdf for the C1622A [your old lcd]

    E
     
  4. MagicMatt

    Member

    Sep 30, 2013
    117
    14
    "I had tried to replace it with standard 16x2 lcd but it didn't work."

    As I discovered myself, there's no such thing as a "standard" LCD. There are several standards, and not all of them the same! The most common seems to be Hitachi-compatible.

    Going from the soldered pins, yout LCD was being run in 4-bit mode.

    The standard interface is 14 pin... you have 16 pins! Why? Because some LCD modules double up the A and K connections on the pins, to make it easier to interface for a backlight. The track will probably be going through a resistor to the LED. If there's no backlight, these most likely wont be connected anywhere, though the tracks will be there since if you buy a version with a backlight all they do is just put an LED onto the board.

    You've got nothing connected to pin3... that controls the contrast. This makes me wonder if the display is working fine, but the contrast is simply so pale it's not visible. I think some LCDs have a default they use if that pin is open circuit - but not all of them do. I usually put a 10k pot between Vcc and Vss with the taper out to that pin, so I can adjust contrast anyway.

    What model LCD did you use to replace it with? Have you checked the spec. sheet for it to see if you need to control contrast manually?
     
  5. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    The three pics I have attached are of customer lcd.
    I have replace it with 16x2 lcd ,but didn't work


    Edit: I had also put a 10K pot, but still lcd does not work, however customer lcd works fine
     
    Last edited: Sep 4, 2014
  6. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,504
    380
    hi,
    I asked in post #3, Are the character pixel blocks visible on the LCD.?
    If not, does varying the 10K contrast post make them visible.?
    E

    Do you have an oscilloscope.?
     
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