No text on LCD 16 x 2

Using Arduino Displays
1

Hi. I'm a massive newbie to this. I've bought myself a 16x2 lcd screen and hooked it up following this tutorial: https://www.arduino.cc/en/Tutorial/HelloWorld?from=Tutorial.LiquidCrystal

I soldered the points yesterday. The board connection itself seems to be working. The potentiometer works, as I can use it to change the brightness/contrast of the display (the darker background blocks appear on the screen when I turn it), but the "Hello world" text doesn't display. I'm not getting any errors with the code.

Any ideas on what I'm missing. The picture probably won't help, but this is how I've hooked it up.

LCDBoard.jpg
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2

Welcome to the group!

To start with, turn the contrast down to the point where the black matrix rectangles just disappear.

3

You have an interesting LCD1602 which appears to have alternative rows for the pin headers. Can you post a link to the supplier's product page ?

LCDBoard.jpg
LCDBoard.jpg3264×2448 938 KB

Since you appear to have the Backligh LED, contrast and power pins correct I guess that it is a wiring error but check very carefully, if there is labeling on the LCD pins, that the labels match those in the tutorial.

Edit:
I found the display Basic 16x2 Character LCD - RGB Backlight 5V - LCD-10862 - SparkFun Electronics
You did notice the two additional pins on it which do not appear in your tutorial ? It does looks like you have counted from the right and got at least at least the connections DB4 to DB7 wrong.

4

It does looks like you have counted from the right and got at least at least the connections DB4 to DB7 wrong.

Actually it looks as if he counted in from both ends which is just as bad and does make the data connections incorrect as you mentioned.

His photo doesn't clearly show the wiring but it does show more than 4 unoccupied pins between the group at the left and the group at the right.

He should wire it in accordance with the Arduino example going from left to right. The final wire, shown in black at the right end, should go into pin 16, 17 or 18 depending on the desired backlight color.

Don

5

Thank you everyone for all your help! I thought I should post the finished product in case someone in the future has the same problem. You were all right, I'd counted in from the right on my board, not realising there were 18 connectors instead of 16 like on non-RGB boards, so my wiring was all kaput.

A bit frustrating because the information, for a newbie at least, isn't that clear and the tutorial the product page sends you to just works from a model that only has 16 pins instead of 18. It DOES mention it briefly on the product page, but I missed that the first time around.

Eventually figured it out though (well, my wife did actually, hence the insisted upon message on the finished version).

I've uploaded an image of the finished version.

I used this tutorial for the wiring and coding: https://learn.adafruit.com/pages/243/elements/2973928/download

This one says that you don't need resistors because they are built into the board, but on the board's product page it says to use resistors or you can burn out the RBG colours.

Additionally, on the schematic for wiring above, it has a red jumper cable going from pin 15 to a positive rail on the side. It was only when I removed this that the board lit up and showed the message, albeit, quite dimly.

When I realised on this datasheet: https://cdn.sparkfun.com/datasheets/LCD/Monochrome/ADM1602K-FS-RGB-FBW.pdf

that pin 15, labelled K, is ground, I put a black jumper cable into a negative pin on the negative rail on the side and it lit up like Christmas.

Don't know if I'm doing this right, or I'm going to blow stuff up, but for the moment, it's working. :slight_smile:

Thanks again for all of your help!

WorkingRGBLCDBoard.jpg
WorkingRGBLCDBoard.jpg3264×2448 754 KB

6

You are an expert now.

Your contrast is still too high.

WorkingRGBLCDBoard.jpg
WorkingRGBLCDBoard.jpg3264×2448 754 KB

My wife is making supper

7

This is on the product page and, as pointed out, your backlight appears to be very bright:

Note: It is recommended to use a current limiting resistor with the backlight colors. You can burn out your LEDs if you do not use a current limiting resistor. Try using a 1k Ohm resistor. The backlight is controlled by pins 18, 17, and 16.

8

Go on. I do not own a RGB backlight display. Regular backlights are just simple LEDs with current limiting resistor.

Typical backlight currents on a 16x2 would be 20mA. This means the resistor would be about 100R for a white LED. 1k0 would be very dim.

Most 16x2 pcb have a footprint for the backlight LED resistor. You should be able to find it by following the copper traces. Some modules have 0R resistors mounted. These need an external resistor to limit the current.

RGB backlights would have separate resistors for R, G, B LED.

David.