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Author Topic: 16x2 lcd with UnoR3 probs  (Read 5376 times)
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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.


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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.
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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.
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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.
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...  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.

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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
« Last Edit: December 04, 2012, 11:10:06 am by floresta » Logged

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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.
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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.
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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
 
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it didnt come alive

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

Or your lcd is toast.
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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.
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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.
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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


« Last Edit: December 10, 2012, 09:16:29 am by knuckles » Logged

Dee Why NSW
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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.
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LONDON UK
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same as my setup is what you see here above
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Dee Why NSW
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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.
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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
« Last Edit: December 10, 2012, 10:45:14 am by floresta » Logged

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