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Author Topic: 16x2 LCD Mystery [update]  (Read 3769 times)
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... is now causing to show about the last 4 or 5 collums black when i turn the potentiometer ...
You very well may have a defective LCD.

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could it be that this lcd is not Hitachi HD44780 Compatible?
It is not likely.

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how does non-Hitachi HD44780 LCD's react to this libary?
They typically work properly

Once again I will recommend that you disconnect all of your wires and start again and carefully follow the tutorial at http://www.ladyada.net/learn/lcd/charlcd.html.

Before you get to the point where you connect the six wires between the LCD and the Arduino you should see a single row of boxes on the top line of your display (the LCD in the tutorial is upside down).  If you don't get that display then there is no sense going any further.


Don
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Once again I will recommend that you disconnect all of your wires and start again and carefully follow the tutorial at http://www.ladyada.net/learn/lcd/charlcd.html.
okey i read that, disconnected everything and when i connect pin15 to 5v (through 220 ohm) and 16 to ground it basicly does nothing, there is no light in there.
the tutorial u send me wich shows an lcd under same connections wich does light up..

does this mean i will have to contact my seller because of a defect? or did i burned it myself?

nick
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does this mean i will have to contact my seller because of a defect? or did i burned it myself?
The backlight seems to have been working in the pictures you posted in reply #4 - so what do you think?

Don
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when i reconect everything i have my backlight back and can see the first row of black collums just like in picture.
when i reconnect everything like post 1 and disconnect the data lines between lcd-arduino, the lcd just shuts down completly
but the strange thing is: when data line 4 (D4 lcd) is connected to the apropiate pin on the arduino (digital 5) -> the lcd is back /online / the circuit somehow is complete agian and i see backlight with collums just like the picture posted before.

and when i disconnect vdd (5+) pin or pin 15 (pin A), only the backlight goes down, i can still see the collums bieng black (1.st row) (note: everything else is conected)
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but the strange thing is: when data line 4 (D4 lcd) is connected to the apropiate pin on the arduino (digital 5) -> the lcd is back /online / the circuit somehow is complete agian and i see backlight with collums just like the picture posted before.

This strongly suggests a wiring error.  This puts us back almost a week to the post that said:  "We need a photograph that allows us to unambiguously follow the six wires that connect between your LCD module and your Arduino."

Don
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It doesn't sound like the LCD is being powered up on it's Vcc Pin (2)... and the device is getting it's power through input protection diodes (Diodes from input pins to BOTH Vcc and Ground)... Pulling D4 should NOT make the LCD Quit working. The LCD is almost CERTAINLY, NOT wired correctly as the LCD will show a black bar where the characters are displayed with pins 1 (Gnd), 2 (Vcc) and 3 (Contrast) connected ONLY. R/S, E, R/W  and data lines would NOT change that. It sounds like the contrast pot is wired correctly (Pot Wiper pin to 3, Pot CCW pin to 2 (Vcc) and Pot CW pin  to 1 (Gnd). However even if those connections are good on the LCD the LCD Vcc pin Must be connected to +5V (Arduino) and the LCD Gnd Pin Must be connected to the Arduino Ground (All at the Arduino  board) FIRST. IMO

Doc
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It doesn't sound like the LCD is being powered up on it's Vcc Pin (2)...
That is my opinion as well.  I've been trying to check his connections for almost a week now.  

Don
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i desoldered all pins except pin 15 (a) and pin 16 (k). acording to the tutorial the backlight should power when connecting pin 15 to 5v through a resistor (220 ohms in my case since i cant find the datasheet) and when pin 16 is connected to ground.

results: just like i said before - > no backlight..

here are some pictures in case you was going to say im not wiring my pins correctly..

thanks for all the efford already,
nick


* DSCF5878.JPG (234.98 KB, 800x600 - viewed 17 times.)

* DSCF5881.JPG (290.59 KB, 800x600 - viewed 15 times.)

* DSCF5886.JPG (285.17 KB, 800x600 - viewed 15 times.)

* DSCF5891.JPG (242.4 KB, 800x600 - viewed 15 times.)
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We need a single (one) photograph that will let us unambiguously see both ends of all of the connections.  It has to be bright enough to reveal detail and it also has to be in focus.

Also - 220 ohms is probably way too high for an LCD backlight.  Is that the size you were using when it worked before?

From the tutorial:
If you can't find the data sheet, then it should be safe to use a 220 ohm resistor, although a value this high may make the backlight rather dim.


Don
« Last Edit: May 25, 2012, 05:12:09 pm by floresta » Logged

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these photo's should do it smiley-wink
i'm sorry for prev photo's.. its just that my camera can't blink the light when its configured as 'close-range-mode'

edit; yes same resistor as all times before

nick


* DSCF5903.JPG (471.13 KB, 1280x960 - viewed 25 times.)

* DSCF5917.JPG (472 KB, 1280x960 - viewed 22 times.)
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i'm sorry for prev photo's.. its just that my camera can't blink the light when its configured as 'close-range-mode'
It's supposed to be sunny all weekend so take it outside for the picture.

Do you have a multimeter that you can use to verify that the backlight LED is drawing current?

Have you tried a smaller resistor?


Don

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It's supposed to be sunny all weekend so take it outside for the picture.
aren't those last two pictures detailed enough?

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Do you have a multimeter that you can use to verify that the backlight LED is drawing current?
no, i am afriad i had killed the fuse of my multimeter some while ago
& no i have no smaller resistors.

where are you looking for? isn't it clear that the connections are correct?

nick
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aren't those last two pictures detailed enough?
No.  I need at least one picture that shows both ends of each of the wires.  It has to be in focus and it has to be correctly exposed.  DSCF5878.JPG might have been suitable except it is is too dark and it is out of focus.

A close-up of your solder connections (both sides) would be helpful as well.  DSCF5891.JPG is close but it is also out of focus and so dark that the black wire is almost invisible.


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no, i am afriad i had killed the fuse of my multimeter some while ago
The voltmeter function frequently works even if the fuse is bad.  Measure the voltage across the resistor and calculate the current.

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& no i have no smaller resistors.
Do you have another resistor that you can put in parallel with the 220 ohm resistor?

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isn't it clear that the connections are correct?
No it is not clear, and Doc agrees with me.

Don
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oh yes, ill look into the resistor to put them parralel with another resistor,
anyway, how come you didn't mention DSCF5903.JPG and DSCF5917.JPG since i thought these were my best pictures sended
edit; i used the voltage meter to messure the voltage on a led, but it just keeps showing 0.00 volt so its broken somehow (i did try to messure both current and voltage on the lcd but it show 0.00)
« Last Edit: May 26, 2012, 10:35:42 am by nickn4 » Logged

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anyway, how come you didn't mention DSCF5903.JPG and DSCF5917.JPG since i thought these were my best pictures sended
DSCF5903.JPG - The resolution is too low.  I cannot tell where the black wire goes at the Arduino end or at the LCD end.  I cannot read the resistor value.

DSCF5917.JPG - The black wire is not visible against the black table.  The resistor value is obscured by the black wire.  The Arduino terminals are not identifiable.

The devices were moved between the times that these two pictures were taken.  Who knows what else changed?



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edit; i used the voltage meter to messure the voltage on a led, but it just keeps showing 0.00 volt so its broken somehow (i did try to messure both current and voltage on the lcd but it show 0.00)
That means that there is no current flowing (assuming that the voltmeter is OK).

Did you try measuring the voltage coming out of the Arduino?  If you measure 5 volts there then you know that the meter is good and something else is causing the problem.  You could have blown out the LED backlight or you could have a poor connection to that backlight.


Don




« Last Edit: May 26, 2012, 11:29:45 am by floresta » Logged

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