Seeking help with 1602 LED display

Hi All,

I'm new learning to use the 1602 LED display using the basic "Hello World" example. All the connections are in line with those in the example and the code was just "copied and pasted" to my board. However, all the screen showing was as per the picture. Checked all the connections and couldn't find anything wrong with them. Also tried different holes on the breadboard but the problem remains.
Any suggestions to rectify the problem will be very much appreciated.

Check the connections. Check the display contrast setting. Replace this ridiculous 9 volt battery with a good power supply.

Thanks flashko. All the connections been checked a couple times. The display contrast in the picture was set to the highest. The 9V battery or proper power both have the same result.

It seems that you have connected something incorrectly, so please post your code.

Thanks fony. please see the code below.

// include the library code:
#include <LiquidCrystal.h>

// Creates an LCD object. Parameters: (rs, enable, d4, d5, d6, d7)
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup()
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);

// Clears the LCD screen


void loop()
// Print a message to the LCD.
lcd.print(" Hello world!");

// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 1);
// Print a message to the LCD.
lcd.print(" LCD Tutorial");

The picture shows that the contrast is set more-or-less correctly, the genuine "UNO" is being powered via the "Barrel jack" which is probably not a good idea but should still work and the unnecessary 220 Ohm resistor is not connected properly to the "A" pin on the display which is why the backlight is not working.

The LCD is not responding to the code, possibly due to faulty wiring and perhaps more likely due to the terrible soldering of the pin header to the LCD module. I cannot see a specific mistake, but it it pretty bad and just as likely something is not connecting.

We have no idea why there is a "smoke alarm" battery sitting alongside and we cannot see any connections to it. Put it away in case you need to replace it in the smoke alarm or your multimeter. :grin:

Not responsible for the problem, but get rid of the connection between the potentiometer and the 5 V line - that is a mistake in most of the frequently copied "tutorials". If it is the 10k potentiometer also always incorrectly specified, connect both ends to ground and it will work better!

Now I see that you have soldered it yourself? Solder all the pins properly again, it seems that you have no contact.

Alone? :face_with_raised_eyebrow:

Please check the solderings.

You need to hold the soldering iron on the joint longer, are you using rosin core solder?

Tom... :smiley: :+1: :coffee: :australia:

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Thank you all for your time. I have to admit they're really terrible soldering. Re-do the soldering again and continuity checked. It's working well now. Appreciate it.

Thank you Tom. Problem solved. Cheers

Hold the soldering iron on the pad and wire until the solder flows like water. When it does you can see it wet the pad and wire. Remove your iron and if impatient like most of us blow on it. I think that will fix your solder joints.

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If you are going to continue in electronics, soldering is an absolutely essential skill.

So it is worthwhile to actually buy some boards and cheap components specifically for practice.

Also get some dud PCB assemblies (should be no shortage of these) and practice removing components (get a solder sucker) and replacing them. Note you generally have to add fresh fluxed solder to properly melt a previously soldered joint.

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