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[SOLVED] 16x2 lcd display problem

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Newbie level 4
Mar 31, 2011
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my 16x2 lcd is working in a PIC development board with sample program of MikroC.
but same connection, doesnt work in my circuit. i dont kno whats wrong.

normally if power is supplied to LCD, dark square boxes will appear on screen. but in my case, i cant get that from my circuit. so, i took it as some kind of power problem. i get the power from a function generator. im using Variable resister for reference voltage pin.

do you have any idea to solve the problem?

Even I faced the same problem when interfacing LCD with some other microcontroller, Check the applied Vdd voltage to the LCD , check for proper grounding of LCD and have u placed a POT for the backlight adjustment if all these are proper then I think the problem might be with your code ie your code is being struck somewhere.

firstly only connect
pin 1-->GND
pin 2-->VCC
pin 3-->pot(10k) varying between vcc and gnd

The backlight should glow and after adjusting the will get black rectangles on one line...lower line

Yes you should probably tell us what lcd you have...atleast the name on the that we can refer to the datasheet

my LCD is LMB162ABC

i think i have problem with reference voltage supply..
i set that as 1V-2V by using resistor and variable resistor..
and need to know the range of the reference voltage...

yes you need to connect a potentiometer(10k would do) at pin 3,
the input to that pin must vary from 0-Vcc...its the contrast adjustment
what is the max voltage has to be given to pin-3 by potentiometer..?
one of my mate says, the range for contrast adjustment is 0V - 0.7V... it means- 0V for high contrast, and 0.7V for minimum contrast. from the potentio meter we need to set that voltage to pin-3. is it correct? i ddint check it that.
Can we Ground the 3rd pin?

Niru just make a small connection...
do not connect your microcontroller right now.
just connect the power...
pin 1-->gnd
pin 2-->Vcc
pin 3-->potentiometer(10k) middle pin(potentiometers other pins connected to vcc and gnd)
pin15(anode)-->330 ohm resistance-->Vcc

turn the potentiometer to see the effect
Check the datasheet of your device you will find these settings i have given above...

Hi friend

I have experiance that
if data line is not connected properly then also this type of problem arise.
Check your data line connection between micro and LCD


thanks all for the valuable advice..

i have solved the problem..

normally potentiometer is used to supply reference voltage to pin-3... so we can adjust the voltage value of pin-3 by potentiometer. the voltage range of pin-3 has become 0V-5V..
before i thought we need to give high reference supply for high contrast..(for LMB162ABC). but for the high contrast, low voltage has to be given to pin-3. it should be 0V-0.7V.. ( 0V for max contrast, 0.7V for min Contrast).
i have grounded the 3rd pin with out using any potentiometer, and got the wright ans..

thank u all..

i have the same code runs smoothly but when i tested it on real lcd, no display is shown. can you help tell me the what's the problem?
16*2 lcd

pin 1 -->> ground

pin 2-->> vcc

pin 3 -->> 1k resistor between ground lcd3.jpg

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