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Topic: Problem with allignment of LCD (Read 1 time) previous topic - next topic

Khalid

Your LCD is good, dont scrap.
Just measured the output voltages of the Arduino input to the LCD. and tell what voltage at what pin you are getting wrt gnd. I think one of your arduino pin out has low voltage (any led, resistor you added)

guyspronck

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But lets go back a step.  What happens when you connect just the backlight, the power, and the contrast (pins 15, 16, 1, 2, and 3)?

Did this, when I put the contrast all the way up only the top row changes contrast. The bottom one doesn't.


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Back one more step - are you using a resistor in series with either backlight lead?


I am not using a resister in series with either of the backlight lead, is this needed?

dhenry

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Any good places to get one?


Tough to know in your backyard but I got mine (48 of them, in one box) years ago from digikey.

floresta


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But lets go back a step.  What happens when you connect just the backlight, the power, and the contrast (pins 15, 16, 1, 2, and 3)?

Did this, when I put the contrast all the way up only the top row changes contrast. The bottom one doesn't.

That is exactly what is supposed to happen.  Most likely your LCD is not defective but personally I wouldn't absolutely declare it good or bad based on what I know so far.

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Back one more step - are you using a resistor in series with either backlight lead?


I am not using a resister in series with either of the backlight lead, is this needed?

These backlight LEDs always require some sort of current limiting.  Sometimes there is a resistor on the pc board, but most of the time you need an external one.  I would start with 150 ohms and see what happens. 

Without this resistor you could damage the LEDs but it is more likely that your power supply is not capable of supplying enough current to do so.  In this case it's output voltage could be dropping and this could possibly be causing the LCD to malfunction.


Don


guyspronck

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Without this resistor you could damage the LEDs but it is more likely that your power supply is not capable of supplying enough current to do so.  In this case it's output voltage could be dropping and this could possibly be causing the LCD to malfunction.[/color]


I put a 1k resister on the backlight and this fixed only the first character. Don't know what it could be really.

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