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1  Using Arduino / Displays / Re: Backlight and I2C on LCD Display on: Today at 02:57:57 pm
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On the LCD board is a five resistor array, 2k2 resistors totalling 11k, from Vo to Vcc defining the six multiplex voltages for the LCD.  The contrast voltage required is generally about 4.5 to 4.8V.  If you put a resistor between 330 ohms and 1k in series with this internal resistor chain, from Vo to Gnd, this will generally provide a suitable contrast voltage.  And the display will generally work (at 4.5 to 5V supply) with Vo connected directly to ground.  Whilst a 10k potentiometer is one way of defining the voltage, 90% of its travel it totally wasted (which is even funnier when it is a ten turn pot!).  A 1k variable resistor (a pot with the wiper connected to one end) makes just as much or more sense.

If using a resistor between pin 3 and GND 'makes just as much or more sense' then I wonder why the vast majority of data sheets that provide any information on how to feed this pin specify using a potentiometer. 

Don
2  Using Arduino / Displays / Re: 1602 LCD Internal contrast and brightness control J1 J2 J3 R1-R9 16x2 on: Today at 09:22:52 am
There are hundreds (probably thousands) of different LCD display modules out there that use the HD44780U compatible controller.  They do not however all use the same circuitry on their pc boards.

I don't think the  brightness of the LCD is adjustable and the contrast of the LCD is almost universally controlled by an external potentiometer.

Pins 15 and 16 have nothing to do with the LCD, they typically provide power to the backlight.  Those resistors may be current limiting resistors for the backlight so you may be able to vary its brightness via the jumpers, but not the brightness of the display itself.

You may be able to power the backlight via connections near one end of the display but you will then need to provide external current limiting resistors.

We will be better able to determine what those resistors do if you provide good photographs of both sides of your module along with a link to it's datasheet.


Don



3  Using Arduino / Displays / Re: 16x2 LCD Scrolling Improperly for array with more then 5 strings on: Today at 09:05:15 am
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Such a helpful article.
Thanks.

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How did you manage to find it ? (Google ? Really ?)
He may remembered it from other posts on this forum over the years.

Finding things in Google relies a lot on using an appropriate search term, one that appears in the material you are searching for.  Determining what search term to use is the hard part.

In this case searching for 'LCD Addressing' will bring it right up (at least here in the USA), but of course you did not know that it was an addressing issue.


Don
4  Using Arduino / Displays / Re: Looking for readable LCD display without backlight on: August 19, 2014, 08:31:13 pm
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Does anyone know such a display ? I see them in devices, but I can't buy a module with such an display.

I guess the real tip-off would be to look for a display with only 14 pins.

Don
5  Using Arduino / Displays / Re: Odd Display Issues with 1602 HD44780 on: August 19, 2014, 08:27:30 pm
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- the only thing connecting them to the Arduino was the wire going to the digital input reading the status of the switch.

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So I removed the separate power supply and made it so that everything was grounded and powered by the Arduino - when I did this all weird behavior stopped...

Now go back and read the first half of reply #1.

Don
6  Using Arduino / Displays / Re: Odd Display Issues with 1602 HD44780 on: August 17, 2014, 09:57:32 pm
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then I soldered it up and it didn't work

Did you remember the connection between the negative terminals of both power supplies?


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I would have attached images but every time I try it crashes - they are compressed and are well within the size limits

Try again.  I think there may be some limitations for your first post.

Don
7  Using Arduino / Displays / Re: [Temporary Solve] new LCD display not properly showing text on: August 17, 2014, 12:17:30 pm
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That actually just indicates an uninitialised display, meaning the HD44780 (clone) has not responded to the initialisation command, and is not generating the strobes for the second line.

I was corrected about this by someone who is pickier than me ( I ??) over on the AVR freaks board.

Actually a single row of blocks (or two out of four rows) indicates an improperly initialized display controller.  Typically the controller has not been initialized by your code so it retains the default initialization that should occur at power-up.  This is for a single line display (a display using a single line of memory, not necessarily a display using a single row of characters).  These single line displays use a a different multiplexing scheme with a different duty cycle, hence the dark row of blocks.  Also the addressing scheme is different when you get beyond the first 40 characters.

As far as we are concerned there is no difference between an uninitialized and an improperly initialized display but the term improperly initialized is the correct one.


Don
8  Using Arduino / Displays / Re: [Temporary Solve] new LCD display not properly showing text on: August 17, 2014, 08:43:43 am
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(code-fragment free for your protection)
Code:
void setup()
{
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("Hello, World!");
  delay(3000);
}

void loop()
{
  lcd.clear();
  lcd.print("Test");
  lcd.setCursor(0,1);
  lcd.print("Second Line");
  delay(3000);
  lcd.clear();
  lcd.print("I'm Alive!");
  lcd.setCursor(0,1);
  lcd.print("Second Line");
  delay(3000);
}

Are you sure?

Don
9  Using Arduino / Displays / Re: [Temporary Solve] new LCD display not properly showing text on: August 17, 2014, 08:38:40 am
The simplest way to test the display does not involve cursor positioning at all.  Just send 80 printable ASCII characters to the display and all of the character positions should be filled.

Code:
#include <LiquidCrystal.h>

//LiquidCrystal lcd(rs,en,d4,d5,d6,d7);
  LiquidCrystal lcd(12, 11, 5, 4, 3, 2);       // put your pin numbers here

void setup()
  {
    lcd.begin(20, 4);                          // put your LCD parameters here
    for (char i=47; i<127; i++)                // send 80 consecutive displayable characters to the LCD
      {
        lcd.print(i);
        delay(100);                            // this delay allows you to observe the addressing sequence
      }
  }


void loop()
  { 
  }

Don
10  Using Arduino / Displays / Re: new LCD display not properly showing text on: August 16, 2014, 08:22:35 pm
Also - this is only a code fragment not a complete sketch which may not be apparent to a beginner. [/color]

Don



gosh really?... its a code fragment?  thanks, I'll try to remember



I guess you didn't comprehend the second half of the sentence.

Don
11  Using Arduino / Displays / Re: QC1602A (v2.0) Contrast not working? on: August 16, 2014, 03:05:00 pm
Some breadboards have a break at the center of the horizontal bus bars that you are using for +5V and GND.  Typically those breadboards also have a break in the blue and red lines painted next to those buses but you never can tell. 

If you don't have a voltmeter to check things out then just connect the potentiometer feeds left of the center of those buses and see what happens.


Don
12  Using Arduino / Displays / Re: new LCD display not properly showing text on: August 16, 2014, 02:52:58 pm
@Bulldog

Positioning the cursor at (0,0) is not required since that is where it is positioned by the lcd.begin() function.

Also - this is only a code fragment not a complete sketch which may not be apparent to a beginner.


Don

13  Using Arduino / Displays / Re: new LCD display not properly showing text on: August 16, 2014, 02:50:11 pm
@turtle

Posting a monstrously huge picture is not necessary and posting any picture without specifying the code that produced it is usually a waste of time and bandwidth.

Is that the result of using the quoted code from Paul?


Don



14  Using Arduino / Displays / Re: LCD always gives black boxes.. on: August 16, 2014, 02:36:28 pm
@hamitrs

You have your resistors connected in series between pin 3 and GND which seems to be working for you but will be no better than connecting pin 3 to GND for many displays.

I would suggest that you start by redoing your soldering.  You are using too much solder and may have bridged (connected) some of the pins.


Don

15  Using Arduino / Displays / Re: LCD always gives black boxes.. on: August 16, 2014, 10:08:41 am
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You must not use the port pins denoted "0-RX" or "1-TX" on the Arduino ...

As I mentioned in the very first reply it is not a good idea to use those pins but "must not use" is overkill.  If you are out of available pins you can frequently use pins 0 and 1, depending on what you are trying to use them for.  

In this case I am pretty sure the LCD will work (if all the other problems are resolved) if you disconnect it while downloading the code and then reconnect it afterwards.


Don
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