I would start by checking for solder bridges between the pins on your LCD.  It looks like you have used a lot more solder than you need.

Don

Hey..i am new n arduino world..so i want some help.
i connect my LCD display(JHD 162a) as per given in http://learn.adafruit.com/character-lcds/wiring-a-character-lcd and uploaded hello world program..but all i get is like in the attached image.I used 20k pot instead of 10k..Will that be a problem?
Thanks in advance!

The 20 K pot is not the problem, something else is wrong.  We will need to see a photograph of your connections and a copy of your code.

Also, change the title of this thread from 'Need help!' to something that reflects what you need help with.

Don

Things have come "so far" that 7-segment LEDs qualify as "retro" - "Oh, that's so 70s!"

I haven't found any mention of 7-segment LED displays in this thread (prior to your post).   Nixie tubes date back a few more decades, to the vacuum-tube era.

Don

I'm trying to use a 16x2 LCD screen with the with the YWrobot shield on the Arduino UNO but the compiler does not seem to recognise the command LiquidCrystal_I2C.h. How can I solve this problem?

I don't think this is one of the built-in libraries, so did you install the library where the Arduino IDE expects to find it?  (http://arduino.cc/en/Guide/Libraries)

If you did, then did you restart the Arduino IDE after you installed the library?

Don

Hi,
Ardunio Uno with hobbytronics  lcd with serial backpack
Have got this working with the demo serial rx code.

Have amended  to show 2 variables on lines 1 and 2 but only shows the value of 1 variable twice.

Has anybody go some code other than the demo stuff they could share?

Cheers
Peter

By virtue of the phrasing of your post you are essentially limiting yourself to getting responses from someone who already has such a display.

IF you were to include some combination of the links to the website where you purchased the device, the datasheet for the device, the demo code that you mention, your modified code, etc. then you might have a better chance of getting input from others who have used similar devices.  

Don

How about something like the Adafruit 'Ice Tube Clock'.  http://www.adafruit.com/products/194

Don

... and I have no idea what I'm doing wrong, could anyone here please help?

Judging from the colors of your wires it looks like you are aware of the fact that your LCD has a non-standard pinout (as do most that have the row of pins below and to the left of the display).

We have to see both ends of each wire as well as the code you used (or at least the LiquidCrystal lcd (...) contents), in order to do any troubleshooting.

Don

Is there any way I can improve the shielding of the LCD?

The problem is most likely not with the LCD itself but with the wires going to it..

Don

Can the rotor AC signal have an influence on the LCD?

Yes. Welcome to the real world.

Are the wires going from your Arduino to your LCD physically separate from those going to the relays?  Do you have 'snubber' diodes across your relay coils?

Don

So I have received a WD-C2401P Display from my engineering teacher, and I am wondering if it is possible, or even compatible to use it with the Arduino Duemilanove w/ ATMega328.

Yes, but not with the LiquidCrystal library since it uses a different controller although the instruction set is similar.

Check out this thread --> http://forum.arduino.cc/index.php?topic=78002.0, especially Reply #5. 

Don

My question is:  Is the code equal with or without shield version?

That depends on how you connect your LCD to your Arduino.  You must make sure that the numbers in the LiquidCrystal lcd (x, x, x, x, x, x) statement match the connections between your LCD and your Arduino.

It would have been a lot clearer if the perpetrators of the tutorial had included at least a few more comments:

Code:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

In the example above the LCD RS pin goes to the Arduino D7 pin, The LCD E pin goes to the Arduino D8 pin, etc.

Code:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);      // put your pin numbers here

On your shield the LCD RS pin goes to the Arduino D8 pin, the LCD E pin goes to the Arduino D9 pin, etc.

Code:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);      // put your pin numbers here

In the tutorial the LCD RS pin goes to he Arduino D12 pin, the LCD E pin goes to the Arduino D11 pin, etc.

It really doesn't matter which Arduino pins you use as long as the connections and the LiquidCrystal led() contents match.  This means that you can use the same code with and without the shield if your LCD to Arduino connections match those on the shield.  

It is much easier, however, to connect the wires so they are easy to follow or so they do not conflict with other devices you have connected to the Arduino, and adjust the code to match.  This is essentially what they did when they designed the pc board for the shield.

So i looked into the potentiometer i have and it says:  W-50K 8009ER...  instrutions say it must be a 10K, could this be the problem ??

That is a 50K potentiometer and it should work correctly as long as you have connected it correctly.  With just the backlight, the power, and the potentiometer connected (LCD pins 1, 2, 3, 15, and 16) you should be able to see blocks on the LCD with the potentiometer at one end and a blank screen with it set at the other end.  The correct setting is when you can just barely see a line of blocks on the top row.

[I edited the post.]

Yes that is what I am talking about... I edited the post.

Which makes my response look idiotic.  Thanks a lot.

So I guess my next question would be is can I leave the pins open and get the display to function while I look for a inverter? Or am I dead in the water until I find one?

The backlight circuitry is entirely separate from that of the LCD controller so there should not be any problems running the display without the backlight.  Whether or not you can see anything depends on the display.  Mine all work fine.

Don

I think you are talking about an 'electroluminescent' backlight in which case you will need an inverter.  The EL backlit displays that I have use a standard 14-pin Hitachi interface for the LCD and the inverter is sized for, and connects to, two pads at the right end of the display.  I have several of these inverters around here somewhere but I haven't seen them in years.

Don

It would help if we knew ALL of the restrictions and requirements of your assignment project. 

If you must use the 8-bit mode for some reason then you should you should consider using port D for the eight data lines as it will make the programming easier.  If you plan to use the bootloader to load your code you may have to disconnect your LCD while doing so and reconnect it afterwards.

Don

... where is PB6 and BP7 in picture2

All of the I/O ports on the ATmega328 chip have dual functions.  The other function for PB6 and PB7 is for the 16MHz crystal.  The circuit in your first drawing must be using the 8 MHz internal oscillator in the chip, thus freeing up those two I/O port pins.

Don