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1  Using Arduino / Displays / Re: LCD current draw on: Today at 05:08:15 pm
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And you left the most amazing thing out, continuity check managed to lit the back light.. Sounds funny but it did

What is amazing about being able to light up an LED by connecting what is essentially a battery with a series resistor to the LED.  You have a 50% chance of lighting it up depending upon which way you apply the connections.


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Also, did anyone ask for the serial of this new LCD? No, so why should i post it? Is it so difficult to ask for it ?

I thought I did ask for it in reply #27.  Also, I guess you didn't get the hint in reply #33.

Don
2  Using Arduino / Displays / Re: LCD current draw on: Today at 02:42:33 pm
It took 5 days and 23 posts before you revealed the actual part number of your original LCD.  We wasted a lot of time on that one.

It's been 2 days and 8 posts since you got your new LCD and we still don't know anything about it.  Is there some reason that you are keeping the identification of this new LCD from us?

Your last post has conflicting information about this new display which we cannot resolve for you or anyone else reading this thread.


"This display is wired exactly as the previous one and it works great."
conflicts with
"That tells me that this LCD's back light will turn on normally if i wire the back light pins 15-16."

Don
3  Using Arduino / Displays / Re: LCD black boxes problem! on: Today at 09:59:10 am
Disconnect the wire from pin 5  (RW) of the LCD - which you presently have connected to pin 11 of the Arduino - and connect it to ground instead.

{Technical comment - wrong descriptor for that configuration!}


We are way beyond those problems if he has followed my outline.

Don
4  Using Arduino / Displays / Re: LCD current draw on: Today at 09:53:25 am
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Contrast control works just as well with just a 5k variable resistor from Vo to the negative supply, since the module contains 10k of resistance back to Vcc and you only ever need to vary the contrast voltage a volt or two from the negative supply.

That would depend upon the specific display since they are not all the same.  As he is now using a new, unidentified, display there is no way to determine if his display is wired the same way as the ones you are familiar with.


Don
5  Using Arduino / Displays / Re: LCD black boxes problem! on: July 23, 2014, 10:21:05 pm
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Maybe I need to disconnect the display while uploading the code. I read this elsewhere on the forum, please guide me about that too.
This would be a suggestion only if you are using pins 0 and 1.

I have no clue about your 'solution'.


Don
6  Using Arduino / Displays / Re: HD44780 LCD being sent incorrect data on: July 22, 2014, 09:57:32 pm
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As of now, connecting the LCD like this (Pin1 to 5V, Pin2 to GND, Pin3 to GND) does not display the test display row of black squares that is expected.

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I have not:
☺shorted the LCD
☺swapped the 5V and GND on the LCD

I have seen at least one datasheet for a device with +5V on pin 1 and GND on pin 2 but the vast majority are the other way around.  You haven't identified your device so we can't check this part out.

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Does it matter that I am running the display in 4 bit mode and leaving the other 4 bits' date lines disconnected?
No.

It's time to start over.
Here is my generic step by step approach that should work:

(1) If the module has a backlight then get it working properly.  This involves only pins 15 and 16 on most LCD modules.  Make sure to use a current limiting resistor if there is none on the LCD module.

(2) Get the power and contrast working properly.  This involves only pins 1, 2, and 3 on most LCD modules.  You should be able to just barely see blocks on one row of a two row display and on two rows of a four row display. 

NOTE:  The Arduino has not been used yet, except as a possible source for the power needed for the first two steps.  Do not try to go any further until this is working.  If you don't see the blocks then no amount of program code will help.

(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.


Troubleshooting:

If you have a 16x1 display and there are blocks only on the left half of the row in step 2 then use lcd.begin(8, 2); in your sketch.

If you still don't get a display then make sure that your wiring matches the numbers in the descriptor (or vice versa).


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

If you get a display but it is garbled or has some other problems then try again with a 'static' sketch, one that displays a simple message on the top row of the display and then stops.  All of your code should be in setup() and loop() should be empty between the brackets.

Code:
#include <LiquidCrystal.h>

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

void setup()
  {
  lcd.begin(16, 2);                          // put your LCD parameters here
  lcd.print("hello, world!");
  lcd.setCursor(0,1);
  lcd.print("it works!");
  }

void loop()
  {
  }

If you are still having problems then we need to see a photograph of your setup that clearly and unambiguously shows all of the connections between your Arduino and your LCD module.  We also need a copy/paste version of the code that you are actually using, not a link to the code that you think you are using.

Don


7  Using Arduino / Displays / Re: LCD current draw on: July 22, 2014, 05:18:29 pm
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And you need a 5k potentiometer between pin 3 and pin 15 to control the contrast.
Not exactly, since the potentiometer has three terminals.  I gave the connections in reply #25.

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The contrast of the back light ?
No, the contrast of the LCD.

Don
8  Using Arduino / Displays / Re: LCD not displaying everything [FIXED] on: July 22, 2014, 08:03:10 am
My point is that they are the same as all the other I/O pins.  You don't have to deal with them any differently than you do any of the so called 'digital' pins.  They can even be accessed like the others, with the numbers 14-19.

Don
9  Using Arduino / Displays / Re: LCD current draw on: July 22, 2014, 07:54:53 am
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... its not exacactly the same with the old one ...
Not many are.

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And i will certainly need advice for the back light!!!
Make sure that we have information to get the correct datasheet so we don't waste as much time on this display as we did on the first.

Don
10  Using Arduino / Displays / Re: LCD not displaying eveything on: July 21, 2014, 07:47:28 pm
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I can't see you have used any of the analogue pins, they can be used just as digital pins if you define them as inputs.
Why are you saying they have to be defined as inputs?  As far as I know they are just like all of the other I/O pins on the chip.  The only thing that makes them 'analog' pins is because the Arduino normally makes use of their "alternate port functions" (datasheet section 13.3).

Don
11  Using Arduino / Displays / Re: LCD current draw on: July 21, 2014, 07:24:19 pm
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...as i posted before, the back light works fine through "A" and "K".
It's probably nice and bright also.  It is most likely the limited capacity of the power source that has prevented your backlight from self destructing.

Look at the circuit diagram on page 19 of the datasheet.


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Should the back light turn on, if i connect pins 15-16 to power and ground , but with nothing else connected on the LCD ?
Yes, but without a current limiting resistor you are again relying on having a power supply with limited capacity to prevent your backlight from being destroyed.
No.  Look at page 6 of the datasheet.  Pin 15 is used to provide a negative voltage to ultimately drive pin 3, and pin 16 is not used.

Look at page 7 to see how to connect your contrast potentiometer.  One end goes to +5v, the other end goes to pin 15 (not GND), and the center goes to pin 3.


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Because i  applied 5V on pin 15 and grounded pin 16, i didn't wire anything else at the LCD, and the back light didn't turn on !!! Should it ?
Same question --> same answer.

Don
12  Using Arduino / Displays / Re: LCD current draw on: July 21, 2014, 07:15:33 pm
So now that we know the real part number of the display (RC1602B-YHY-CSVD) we can look at the datasheet and get information about the backlight (in section 14 on page 19).

The 'note' on that page says this:
Note:  The LED of B/L is drive  by current only,  Drive voltage is for reference  only.  Drive voltage can make driving current under safety area (current between minimum and maximum).

This is entirely consistent with what I posted in reply # 19.  Basically, after you get past the fractured English, it is saying that the important consideration is the current rating.  If you try to drive it with a voltage source you may get too little current (and it won't light) or too much current (and it will light brightly, for a relatively short period of time).

Don
 
13  Using Arduino / Displays / Re: LCD black boxes problem! on: July 21, 2014, 02:02:08 pm
That is what the LCD display should look like after step 2 although your backlight looks quite bright.

Now go ahead with steps 3, 4, and 5.


Don
14  Using Arduino / Displays / Re: My lcd only show squares on: July 21, 2014, 01:57:35 pm
Your display has serious problems most likely due to poor connections between the LCD 'glass' and the pc board. 

These connections are made by 'zebra strips' and there have been numerous threads with information about them.

The search capabilities of this forum software is abysmal, even if you find the camouflaged search box.  Try the following Google search: "LCD zebra site:arduino.cc".


Don
15  Using Arduino / Displays / Re: 16x2 goes blank after few hours. on: July 21, 2014, 08:52:19 am
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On several occasions I had the idea that the LCD went blank right after it turns of a relay which is powering an exhaust fan. Not sure if its related,  I just noticed it.

You should pursue this a bit further.  Temporarily replace your relay (and any other inductive devices you are controlling) with an LED and I think you will find that your problem goes away.

Don
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