Arduino Forum

Using Arduino => Displays => Topic started by: mysqo on Dec 01, 2012, 09:44 pm

Title: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 01, 2012, 09:44 pm
Hi!

It seems I got the famous problem with the lcd. The letters wont appear.
Its a 16x2 blue lcd.

Have checked the cables over and over again and I find it correct.
The LCD starts and the backlight shows, but not the letters.
Sometimes the white boxes flashes a millisec or so, then disappears.

Im followed the Hello world guide wich comes with the arduino.
I got the 10K potentiometer. And I have tried with and without it, same result.
I also cant change the contrast with the potentiometer coupled on. Ive
checked the outputvoltage on it,and it works!
Anybody that got an idea? Can link a video if someone want a look.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 01, 2012, 11:46 pm
Quote
Have checked the cables over and over again and I find it correct.

I have heard that before.

Quote
The LCD starts and the backlight shows, but not the letters.
Sometimes the white boxes flashes a millisec or so, then disappears.

Are you using a current limiting resistor with your backlight?

Quote
I got the 10K potentiometer. And I have tried with and without it, same result.
I also cant change the contrast with the potentiometer coupled on.

You must use the potentiometer and you must get the contrast working before you proceed any further.  
If you can't get a row of boxes to appear then you are wasting your time trying to display any text.

Quote
Ive checked the outputvoltage on it,and it works!

Explain what voltage(s) you measured and why you think it works.  When it really works you will be able to see a row of boxes on the screen.

We really can't give more help without more information.

Don




Title: Re: 16x2 lcd with UnoR3 probs
Post by: marcello.romani on Dec 01, 2012, 11:54 pm
Quote
We really can't give more help without more information.


Like code and schematics.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 02, 2012, 02:20 am
Video would be fine as long as its quality is high enough to tell how the connection is made.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 02, 2012, 02:18 pm
When I checked the potentiometer,I used a voltmeter and looked at the output voltage when the arduino was running and only coupled in the voltage from the arduino.I think the potentiometer works because it gives diffrent voltage to the LCD. It also changes the contrast a liiiiiitle liiiitle bit.
Little bit hard to see it in the video tho.
Here is the video: https://vimeo.com/54703995

Here is a clearly pic of how I wired everything, and a pic I got from the manual to compare with.
http://tinypic.com/view.php?pic=2ldubtt&s=6

Here is a video showing how the white boxes flashes when I turned the potentiometer with everything wired:
https://vimeo.com/54704282

Here is the manual for the LCD from the manufactor:
http://www.kjell.com/.mvc/Document/File?id=b6e33422-63ff-48be-b140-a04a0114d7ef

And here is the code I was runnning with everyting coupled in the pic:

#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  lcd.begin(16, 2);
  lcd.print("hello, world!");
}

void loop() {
  lcd.setCursor(0, 1);
  lcd.print(millis()/1000);
}


Title: Re: 16x2 lcd with UnoR3 probs
Post by: marcello.romani on Dec 02, 2012, 02:45 pm
I've tested you sketch on my lcd+keypad shield and it worked perfectly. I just had to change the pin numbers because the lcd on my shield is wired differently than you test setup.

So I think there must be something wrong with your connections...
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 04:04 pm
Quote
I've tested you sketch on my lcd+keypad shield and it worked perfectly.

Why wouldn't it work?  It's the 'Hello World' example sketch that comes with the IDE. 

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 04:08 pm
Quote
Here is the video...

You don't have to even run the first video to see the first (and possibly the only) problem.

You must solder the connections to your LCD module.  A row of header pins (or very short stiff wires) would be the best choice, then you can plug the module directly into the breadboard.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: Tumbleweed on Dec 02, 2012, 04:13 pm
Since I can't see any solder that usually runs through the holes along with the wires that connect to your LCD, I'm going with not soldered wires or at least a cold solder joint.
TomJ
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 04:15 pm
Quote
Here is a clearly pic of how I wired everything...


Look in the lower left box in the 'Description of Terminals' and you will see that the backlight must be supplied with no more than 4.5 Volts.

This means that you must use a series resistor to drop the voltage and at the same time limit the current through tbe LED backlight.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 04:32 pm
Quote
I think the potentiometer works because it gives diffrent voltage to the LCD. It also changes the contrast a liiiiiitle liiiitle bit.

You should be able to vary the voltage at pin 3 from 0 to 5 Volts (with respect to pin 1).  The display should be blank at +5 Volts and you should have a single solid row of blocks at 0 Volts.  The proper setting, which will still show the blocks, will be around 0.4 Volts for your LCD.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 02, 2012, 05:49 pm

Quote
Here is a clearly pic of how I wired everything...


Look in the lower left box in the 'Description of Terminals' and you will see that the backlight must be supplied with no more than 4.5 Volts.

This means that you must use a series resistor to drop the voltage and at the same time limit the current through tbe LED backlight.

Don


I've recently tested to connect the backlight to the 3v pin on the arduino instead. But its the same. (Ive solder the wires on the backside of the LCD)
Could I have destoyed the backlight when I wired it to the +5V?

Will buy the headers tomorrow and solder it.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: bperrybap on Dec 02, 2012, 05:52 pm
Don, Dr,
I think I now understand a potential reason why we are seeing so many newbies not soldering
their connections to the LCD.
It is the Arduino Tutorial:
http://arduino.cc/en/Tutorial/LiquidCrystal (http://arduino.cc/en/Tutorial/LiquidCrystal)

Nowhere in there does it ever mention needing to solder the connections
to the LCD module.
It shows them soldered in the photo, but it never says it in the text/instructions.
In fact it doesn't even list solder in the h/w requirements.
Ignoring the obvious typo of "LED" vs "LCD" this is really the only instructions:
Quote
To wire your LED screen to your Arduino, connect the following pins

And then a fritzing diagram below.

So the issue is that users can follow the tutorial to the letter and have everything
"wired" correctly and end up with a non working or even semi working LCD because the tutorial fails
to mention the requirement of soldering the connections to the LCD.

Unfortunately trying to get the Arduino team to change anything is worse
than pulling teeth. But clearly this needs to get updated.

I opened issues
https://github.com/arduino/Arduino/issues/1149 (https://github.com/arduino/Arduino/issues/1149)
http://code.google.com/p/arduino/issues/detail?id=1116 (http://code.google.com/p/arduino/issues/detail?id=1116)

Note: It appears that github is now being used for issues but I wen't ahead
and put it on the google code page as well.

--- bill
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 06:03 pm
Quote
I've recently tested to connect the backlight to the 3v pin on the arduino instead.

Regardless of how you power an LED you still need some way to limit the current and this almost always involves the use of a resistor.  

Depending upon the LED configuration in the backlight circuit the 3 V supply may not provide enough voltage and/or current to work properly.

You should power the backlight from a 5 Volt supply using a resistor in between the supply and one of the backlight pins.  Unfortunately your data sheet does not supply enough information to determine the required resistance so you will have to experiment.  I would start out with about 150 ohms and see if the voltage across the LED is then within specifications and if the backlight is sufficiently bright.

Quote
Could I have destoyed the backlight when I wired it to the +5V?

You didn't help it or the Arduino power supply at all, but you probably didn't destroy either of them (yet) either.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 02, 2012, 06:05 pm
Quote
Unfortunately trying to get the Arduino team to change anything is worse than pulling teeth. But clearly this needs to get updated.

That is the understatement of the year.

Quote
It appears that github is now being used for issues but I wen't ahead and put it on the google code page as well.

This doesn't help the fact that most beginners rely on the 'official' Arduino pages as gospel truth and mere mortals cannot correct those pages even when they are blatantly incorrect, incomplete, or obsolete.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 02, 2012, 06:07 pm

Quote
I've recently tested to connect the backlight to the 3v pin on the arduino instead.

Regardless of how you power an LED you still need some way to limit the current and this almost always involves the use of a resistor. 

Depending upon the LED configuration in the backlight circuit the 3 V supply may not provide enough voltage and/or current to work properly.

You should power the backlight from a 5 Volt supply using a resistor in between the supply and one of the backlight pins.  Unfortunately your data sheet does not supply enough information to determine the required resistance so you will have to experiment.  I would start out with about 150 ohms and see if the voltage across the LED is then within specifications and if the backlight is sufficiently bright.

Quote
Could I have destoyed the backlight when I wired it to the +5V?

You didn't help it or the Arduino power supply at all, but you probably didn't destroy either of them (yet) either.

Don


Thanks for the help so far!!
Will buy everything tomorrow, and come back with the result.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 02, 2012, 09:27 pm
Bill,

I wishto make a video of how to hook up a character display for while but didn't have time. I bet even with a video, there is no way to make it official.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 04, 2012, 12:26 pm
Ok, I think this is kind of embarrassing..

I havent noticed the pinmarks on the backside of the lcd, because the gudie I followed was for just the same lcd.

But here is a pic of the backside of my lcd : http://oi46.tinypic.com/30tqeio.jpg

Is it true that the first pin to the left is my number 15 and next is 16?
Because I thougt the very first pin to the left was my pin number 1.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 04, 2012, 04:53 pm
Quote
...  because the gudie I followed was for just the same lcd.

I must have missed the place where you told us about this guide.  Surely you don't mean the 'Hello World' example because that display obviously has the pins in a different location.

Quote
Is it true that the first pin to the left is my number 15 and next is 16?

According to your datasheet (page 2) the end pin is the backlight anode (+) and the one next to pin 1 is the backlight cathode (-).

I bet that when you get it working you are also going to find that you have been looking at your LCD upside-down.  The LCD's with the row of pins at the top left seem to universally have the pins as you expected, pin 1 nearest the edge of the board and pin 14 (or 16) nearest the center.  The LCD's with the row of pins at the bottom left usually have a different layout, and they are not all the same. 

Now that I think about it I have not yet run into a display with the pins at the upper right, so yours may be a new (to me) variety.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 04, 2012, 09:50 pm
I found a similiar LCD (if its not the same) , with exactly the same boarddesign, and numbers of the pins : http://www.produktinfo.conrad.com/datenblaetter/175000-199999/181664-da-01-en-LCD_MODUL_STN_POSITIV_LED_WEISS_16X2.pdf

Anyway, when I wired only the VSS and the VDD from the LCD to my arduino (just making sure the LCD worked) it didnt come alive, not a sign, so, I suppose it must be broken.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 04, 2012, 11:42 pm
How does the LCD come alive if you just wire up Vss and Vdd? You should at least hook up pin 3 to potentiometer and see if contrast can be adjusted.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 05, 2012, 12:16 am
Quote
Anyway, when I wired only the VSS and the VDD from the LCD to my arduino (just making sure the LCD worked) it didnt come alive, not a sign, so, I suppose it must be broken.

You have to do something with the contrast pin in order to determine if the LCD is 'working'.  If you leave it disconnected it will 'float' and the resulting voltage at pin 3 will probably be a lot more than the required 0.4 volts (see reply # 10).  Your LCD will then be blank and will appear to be 'dead'.

The best approach is:
(1) Get the backlight working properly.  This involves only pins 15 and 16 on your LCD module.
(2) Get the power and contrast working properly.  This involves pins 1, 2, and 3 on your LCD module.
  The Arduino has not been used yet, except as a possible source for the power needed for the first two steps.
(3) Connect the LCD R/W pin (pin 5) to GND.
(4) Connect the six control and data wires between your LCD module and your Arduino.
(5) Upload your sketch and it should work.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: dhenry on Dec 05, 2012, 02:15 am
Quote
it didnt come alive


Wire the Vo pin to ground. You should see some black bars on the lcd.

Or your lcd is toast.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 07, 2012, 09:38 pm
Ok, I got the contrast working now, I can se the bars.. But to get the volts down to 4,2 on my pin 15, I needed a 560K resistor... And when I got that volt it didnt light up.
So I think my backlight must have been broken.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 07, 2012, 10:11 pm

Ok, I got the contrast working now, I can se the bars.. But to get the volts down to 4,2 on my pin 15, I needed a 560K resistor... And when I got that volt it didnt light up.
So I think my backlight must have been broken.


Contrast working is good news. The lcd may be working after all. The 560K is way too big. You will need no more than 560 ohms.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: knuckles on Dec 10, 2012, 03:02 pm
he has the same problem as me, and i have noted the stern instructions that all the wires should be soldered to the LCD ,but having looked at the videos on youtube regarding  connecting UNO to LCD ,none of them are soldered ,just having wires plugged in to a breadboard and they are all working just fine !
so how do you explain that ?

here is one thats the same as mine except no hello world display


http://www.youtube.com/watch?v=2qfZPYmIo94
Title: Re: 16x2 lcd with UnoR3 probs
Post by: NickPyner on Dec 10, 2012, 03:40 pm
The setup you show is exactly what one would expect There will be a pin row soldered to the LCD module and that is plugged into the solderless breadboard. The plug-in wires are then run to the pot and the Arduino.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: knuckles on Dec 10, 2012, 04:04 pm
same as my setup is what you see here above
Title: Re: 16x2 lcd with UnoR3 probs
Post by: NickPyner on Dec 10, 2012, 04:33 pm

same as my setup


It probably isn't the same. His works, yours doesn't, and you can't see his wiring anyway. As I have said before, the wiring is probably where the problem lies, and that clip is no help. You should be able to use the hello world sketch that comes in the examples. You don't need to download anything, and certainly not the Freetronics sketch.

The standard sketch has all the details for the wiring and thus can be used with any 16x2 LCD. While the sketch is, like tronixstuff, usually seen for use with a shield, that is immaterial. Your breadboard serves the same purpose. The code is only interested in the Arduino pins. You have to connect the correct wires from the LCD  to them. There is a bit more about that here.

http://arduino.cc/forum/index.php/topic,136739.msg1027516.html#msg1027516

I think you are actually at an advantage with the bare LCD like yours. It is more flexible, and gives you more choice, than a shield.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 10, 2012, 04:42 pm
Quote
he has the same problem as me, and i have noted the stern instructions that all the wires should be soldered to the LCD ,but having looked at the videos on youtube regarding  connecting UNO to LCD ,none of them are soldered ,just having wires plugged in to a breadboard and they are all working just fine !

I think you are misinterpreting something, perhaps what has to be soldered.

If you reread reply #4 you will see that it says "You must solder the connections to your LCD module."

In that case the LCD module has wires connecting the module to the breadboard while the video that you have submitted in reply #25 has pins connecting the module to the breadboard.

In reply #4 the connections (wires) are not soldered to the LCD module whereas in reply #25 the connections (pins) are soldered to the LCD module.

As you have correctly stated in both cases the wires (or pins) are simply plugged into the breadboard, not soldered.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 10, 2012, 05:03 pm
To make it a bit more clear for the newbies regarding connection, only these are proper for connecting two metals for electrical conduction:

Solder the metals together.
Eg. The pins in that video are soldered to the metal contacts on the display.

Use spring-loaded mechanism to hold one metal against another.
Eg. The row of pins are pushed into breadboard holes. There are spring clips under the holes to hold metals together. Same goes with the jumper wires inserted in the breadboard.
Eg. There is a "spring" type of contact inside Arduino board's female headers. If you insert a square pin in a female header, the "spring" holds the square pin. Round pins will have worse contact with arduino headers so you may expect some issues.

Certainly you may use welding (fusing two metals) or gluing (conductive glues), or other less obvious spring-load ways (wire-wrapping, wire nuts) but if you just jam the lead of a wire into a hole, it won't be sufficient. My rule of thumb is: if you can easily pull the contacts apart, they are likely not making good electrical contacts. Hope it helps.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: bperrybap on Dec 10, 2012, 05:40 pm
knuckles,
It takes only a few minutes to wire up an LCD to an Arduino
It takes even less time to for an experience person to be able to detect
a wiring error or mismatched LiquidCrystal constructor if
all the non working information supplied.
The needed information is:
- the full sketch being used
- A clear photo that shows all the wiring

If you would supply both of those your problem would be resolved
very quickly.

--- bill
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 10, 2012, 07:30 pm

knuckles,
The needed information is:
- the full sketch being used
- A clear photo that shows all the wiring


floresta said it, Nick Gammon said it, now Bill said it again. I wonder how many forum members will it take to get knuckles to respond to these reasonable requests.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 10, 2012, 08:29 pm
I still think he faithfully followed that "really nice wiring diagram" back in the other thread --> http://arduino.cc/forum/index.php/topic,136463.msg1026929.html#msg1026929 <--  and that his connections are exactly backwards.  A photo would prove or disprove my theory.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: JoeO on Dec 11, 2012, 04:42 am

he has the same problem as me, and i have noted the stern instructions that all the wires should be soldered to the LCD ,but having looked at the videos on youtube regarding  connecting UNO to LCD ,none of them are soldered ,just having wires plugged in to a breadboard and they are all working just fine !
so how do you explain that ?

here is one thats the same as mine except no hello world display

http://www.youtube.com/watch?v=2qfZPYmIo94

Nick Gammon asked you to:

"@OP (knuckles): start a new thread please, describing your problem in detail.

Post a link to the exact LCD you are using.

Post a photo of your connections. A clear photo.

Post the code you are using, inside code tags.

Thanks."

You have hijacked someone else's thread.  This is rude.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 11, 2012, 04:57 am
Quote
You have hijacked someone else's thread.  This is rude.


It's not nearly as rude as the language he used in reply#6 of the original thread --> http://arduino.cc/forum/index.php/topic,136463.msg1025335.html#msg1025335 <-- before it was removed by a different moderator.

Don 
Title: Re: 16x2 lcd with UnoR3 probs
Post by: knuckles on Dec 11, 2012, 10:22 am
look guys its a simple wiring job ,NO, the pins 1-16 are not connected backwards do you think i am stupid ?,i have 1-16 numbered on both sides of the display and theyre all wired u p as the youtube example above ,all very simple stuff .i have worked in electrical engineering all my life .
the codeing is as i have posted .i will try the different numbers in the code when i have time to do it ,i have more important things to do ,like wife and family, job and earning ,and other hobbies ,arduino stuff is low down my priorty of things to do .
Title: Re: 16x2 lcd with UnoR3 probs
Post by: NickPyner on Dec 11, 2012, 12:06 pm

theyre all wired up as the youtube example above ,all very simple stuff


In that event, my curiosity is getting the better of me. Looking at the youtube, there is a long blue wire connected to #6 "E" on the display. Can you tell me what Arduino pin this is connected to?
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 11, 2012, 04:28 pm
Quote
do you think i am stupid


Well, you are the one who brought it up so here is your answer.  

I do not think you are stupid, I think you are ignorant. 

You are also proving that you are intransigent.

Don

Title: Re: 16x2 lcd with UnoR3 probs
Post by: knuckles on Dec 11, 2012, 04:31 pm
i am chucking them back in the shoebox till next year i cant afford to waste any more time on these LCD displays .the display on the Pololu orangatan works ok for now .
i might try a few new ones next year in case theyre faulty .
thanks for your input anyway
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 11, 2012, 06:27 pm

i am chucking them back in the shoebox till next year i cant afford to waste any more time on these LCD displays .the display on the Pololu orangatan works ok for now .
i might try a few new ones next year in case theyre faulty .
thanks for your input anyway



I felt bad that you didn't get a good experience with arduino projects. If you did, it could take up a lot of your free time and provide both fun and functionality. As everyone else here must be, you are the master of your own domain, i.e. your job and family besides being good at wiring. I am sure that everyone in your circle respects you. But you are in a new place now, this forum. All that respect you receive automatically from your job and family is left where they are and new respect is earned not brought here.

You didn't do it the right way from the start. If you showed a picture or two, your code accompanying the pictures, you will be well respected among us as an eager learner and people usually bend backwards to help you. You didn't. After multiple members requesting photos you didn't do it, only quoting you are good with wiring, which we don't know. We don't know your name, your face or what you are good at. What me know is what you posted, which is very little about this project you are doing. Tell me that we should simply trust you with your wiring. How does that sound to you if it were someone new at your work telling you they know everything and you should put full trust on them. As experienced at work as you are, this may have been the first time you are removed from your own comfort zone in your own home or work space and have to be treated as a newbie. You probably experience that a lot if you have to frequently change jobs.

I am not calling you stupid or anything, maybe newbie shock. Stupid is reserved for repeated offenders. You are only upsetting some of us with one thing and we forget and forgive or in my case just forget. I am hoping you will come back with some other projects to share and learn with us soon.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: knuckles on Dec 13, 2012, 03:11 pm
situation now resolved after i bought a cheapie display of ebay ,it was a 5 minute job to get it working ,looks like a faulty display was the problem.
all sketches working fine with the new display .
Title: Re: 16x2 lcd with UnoR3 probs
Post by: liuzengqiang on Dec 13, 2012, 06:01 pm

situation now resolved after i bought a cheapie display of ebay ,it was a 5 minute job to get it working ,looks like a faulty display was the problem.
all sketches working fine with the new display .



Happy for your.
Title: Re: 16x2 lcd with UnoR3 probs
Post by: JamesD3rd on Dec 18, 2012, 07:38 am
Something else to consider.

When you see the row of pins start at #15 & #16, then 1-14, it might be a non-backlit LCD display.

I have several different 16x2 character displays, and of the 3 that are not backlit, 2 have the goofy pin orientation.

With those pin 15 & 16 are not connected.  
Pin 1 & 5 - ground
pin 3 - 10k pot OR resistor to ground (8k-9k)
pin 2 - 5v
pins 4,6,11-14 connected to arduino digital pins

Adafruit has a wonderful tutorial which I still use as a reference.  Never hurts to double check connections before heating the iron.

http://learn.adafruit.com/character-lcds/wiring-a-character-lcd
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 18, 2012, 03:34 pm

Something else to consider.

When you see the row of pins start at #15 & #16, then 1-14, it might be a non-backlit LCD display.

I have several different 16x2 character displays, and of the 3 that are not backlit, 2 have the goofy pin orientation.

With those pin 15 & 16 are not connected.  
Pin 1 & 5 - ground
pin 3 - 10k pot OR resistor to ground (8k-9k)
pin 2 - 5v
pins 4,6,11-14 connected to arduino digital pins

Adafruit has a wonderful tutorial which I still use as a reference.  Never hurts to double check connections before heating the iron.

http://learn.adafruit.com/character-lcds/wiring-a-character-lcd

The LCD interface as designed by Hitachi is and always has been 14 pins.  The original backlights were electroluminescent and required a high voltage (>100 v) to operate.  The connections were at the end of the display.  When LED backlights became common pins 15 and 16 were added but those pins have nothing to do with the LCD.

Some displays have two rows of 7 (or 8 ) pins at the end of the display but most have one row of 14 (or 16) pins along the edge.  From what I have seen the majority of displays have those 14 (or 16) pins at the upper left edge of the display and the pins are in numerical order starting with pin 1 near the edge of the board and with pin 14 (or 16) near the center.

I have also noticed that the displays with the pins at the lower left edge of the display are the ones that are likely to have their pins in a different order and the order of the pins is not always the same.  This appears to be the kind of display that you have.  Other than the pin order, you have described what are perfectly ordinary LCD connections.  You have to pay special attention to the markings on the pc board and/or the datasheet with these.

The Adafruit tutorials are quite helpful but you have to be careful when it comes to wiring the backlight.  The tutorial has evolved over the years and the pictures have pretty much stayed the same while the text seems to vary a bit. The displays that they sell typically have a current limiting resistor for the backlight on the pc board so there is no need for an external resistor and none is shown in the photographs.  Their text currently does mention that some (I believe this should be most) displays require an external resistor but this text seems to come and go or maybe I just missed it.

Also, be aware that the photos in that tutorial up to the 'Bus Wiring' section all show the display upside down.  The last photograph in the 'Contrast Circuit' section shows the single row of blocks that you should expect to see in the upper row but they appear to be in the lower row because the display is upside down.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: JamesD3rd on Dec 19, 2012, 08:01 am
Good info -

I went back and looked at the tutorial again - oh yeah no resistor on the LED connection ;)

Seems to be a good idea to use the limiting resister for the backlight on all displays
unless you need the full brightness of the back light.....
Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 22, 2012, 04:12 pm
Ok. Now I've got a brand new display. Ive solder a header on it, then made the right connections. Anyway the LCD's backlight wont light up.
And yes I have tried from the beginning with resistors. I've started on 680 ohm resistor and then went down to a 560,470,390,330,270,180,150 and now a 100 ohm, still this stupid backlight wont show up.
Here's a pic with little more Christmasfeeling..
(http://oi48.tinypic.com/2nhgjgg.jpg)

Now when I thougt of it.. When I had my old display and the wrong connections the backlight went up at least.
Like here: https://vimeo.com/54704282
Something is very mysterious with this special lcd.
Seems like the LCD from usa on ebay is much more easy than this model.
http://www.ebay.com/itm/1pcs-1602-16x2-HD44780-Character-LCD-Display-Module-LCM-blue-blacklight-New-/281040213404?pt=LH_DefaultDomain_0&hash=item416f4d559c

Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 22, 2012, 04:14 pm
And here is the code :

#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  lcd.begin(16, 2);
  lcd.print("Hello arduino.cc!");
}

void loop() {
  lcd.setCursor(0, 1);
  lcd.print(millis()/1000);
Title: Re: 16x2 lcd with UnoR3 probs
Post by: floresta on Dec 22, 2012, 08:45 pm
The code and pins 1 <--> 14 have absolutely nothing to do with the backlight.  

The backlight is basically an LED or more likely an array of LEDs that you can treat as a single LED.  

You need the positive lead of a 5v DC supply connected through a resistor to the anode (+) side of the backlight and you need the negative lead of the 5v DC supply connected to the cathode (-) side of the backlight.

So, as long as the backlight is still good, and they are relatively hard to destroy, you just have to get the anode and cathode connections identified.  The problem is that your datasheet has conflicting information.  The 'Mechanical Diagram' shows the end pin as (+) but the 'Description of Terminals' on the next page implies that the end pin may be (-).

You have wired your circuit in accordance with the 'Mechanical Diagram' so I would now try it the other way.  Move the blue wire from pin 15 to the (+) line and move the purple wire (attached to the resistor) to the (-) line.  This puts the resistor in the cathode lead instead of the anode but that's ok.

Don
Title: Re: 16x2 lcd with UnoR3 probs
Post by: dhenry on Dec 22, 2012, 09:40 pm
Why don't you just flip the polarity of power to the led and see if it works that way.

It shows you how valuable a datasheet is.

Title: Re: 16x2 lcd with UnoR3 probs
Post by: mysqo on Dec 22, 2012, 11:38 pm
Finally! Thanks for all help! Really appreciate it:D
(http://oi47.tinypic.com/2cne5c1.jpg)