Arduino LCD not working

Lena Jhon's picture

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Joined: Dec 09, 2019

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Arduino LCD not working
December 9, 2019 - 9:20pm

Hey I am very new to electronics I am trying to get my LCD to work with Arduino but it's not working. I want to learn how to debug my lcd to check where the probelm is. I have tried many forums but nothing helped. 

Please dont ask me to check the connection and circuit diagram. I have done it many times. I have also replaced the display and Arduino nothing changed. My circuit diagram and code is same as given here

https://circuitdigest.com/microcontroller-projects/arduino-lcd-interfacing-tutorial

Please help. My display shows only plain white screen all the time 

Sourav Gupta's picture

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Joined: Feb 12, 2018

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Double check the resistance value.
December 9, 2019 - 10:16pm

I hope you are running exactly same code as given in the tutorial.
Double check the value of resistor associated with the lcd. If it is not proper the lcd will show nothing.

Lena Jhon's picture

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Current limiting resistor 1k
December 10, 2019 - 11:05am

The only resistor used in the circuit is a current limiting resistor for the LCD backlight. I have used a 1k resistor and the backlight is on. Is it okay to use 1k for this?

Thanks for the reply

Debasis Parida's picture

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Joined: Aug 22, 2019

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Check Contrast pin connection
December 9, 2019 - 11:37pm

If your LCD is having a plain screen, then it might be the issue of pin 3 of  LCD which refers to the contrast pin.Check the pin 3 of LCD weather it is properly grounded or not.If your contrast is OK, then it should show a screen like the figure below instead of a plain screen.If it doesn't work, then try connecting a potentiometer at pin 3 of LCD, so that you can control the contrast of LCD.your LCD should show a screen like below without uplading the code.

Lena Jhon's picture

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Great this solved my problem
December 10, 2019 - 12:22pm

Thanks Parida, you saved my day. 

The problem was with the contrast pin I added a pot and controlled the contrast and everything works now. But should I always have a POT? I want my circuit o look small, is there a way to use a simple resistor? if yes what value ?

Debasis Parida's picture

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Using Potentiometer to change the contrast
December 10, 2019 - 5:18pm

Hi Jhon, great to know that, your issue has been resolved.It is reccommended to use a potentiometer for contrast adjustment, as you can vary it as per your need. Yes, if you want to use a resistor instead of it, try connecting a 1K resistor, with one end connecting to pin 3 of LCD and other to ground.Hope it helps!!!

Lena Jhon's picture

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Joined: Dec 09, 2019

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I use two resistors as potential divider
December 13, 2019 - 11:35am

Hey thanks, once I got the right constrast value on my lcd I measured the resistance between the two exterme pins from my center pin of POT. The values were 2.2k and 7.8k approx. 

Then I replaced the pot with two through hole resisters and it worked. My the sad part is when I change the LCD display the conrast value also changes. Looks like the value of these resistors will have to vary for every LCD panel. 

Debasis Parida's picture

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Joined: Aug 22, 2019

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Depends on Electrical characteristics of LCD
December 13, 2019 - 10:50pm

Hey Jhon, it seems that, the LCD you have replaced may have diffrent electrical property which needs recalibration.So it is wise to use a 10K pot with Pin 3 so that you can just calibrate it anytime.

Muhammad Umar's picture

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Vary Contrast with Potentiometer
April 29, 2020 - 8:38pm

The issue you are facing is very common for the beginners, but easily solvable. For that cross-check pin 3 of your LCD if it is 16 x 2 type of LCD. You have to attach a potentiometer of value 10k. After this power up your system and rotate the nob of the potentiometer you just connected. There is a level comes, where you can easily see the characters on the screen. Here I would like to suggest you to get assistance from SSLA technical support team, who assist the beginners for the completion of their projects.