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Author Topic: LCD contrast not working  (Read 3766 times)
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Italy
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Hi all,
i've bought an HD44780 blue 16x2 LCD (JD162A) and i'm trying to make it working but i find a problem.
The contrast of the screen doesn't change. When it's on i can only see the screen lighted.
i followed the instruction of examples on the IDE without any good feeds...probably i don't know exactly where to put the resistor but i think i tried in all the possible way.
the last configuration i've followed is this:
* LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * 10K resistor:  where this one?
 * LCD  pin 15 and LCD pin 16 to +5V and ground
 * LCD VEE to the potentiometer 10k

i think i'm doing something wrong but i don't know what and, in case this is right, i don't know how to understand if the LCD doesn't work as it should.
can somebody help me please?

thanks in advance
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India
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JHD16A it is working with arduino duemilanove.
Please check:
 1 (VSS)    GND Arduino pin*
 2 (VDD)    + 5v Arduino pin
 3 (contrast)    Resistor(2K) to GND Arduino pin*  pin13|---/\/\/\/-------ArduinoGND
 4 RS                    Arduino pin 12
 5 R/W            Arduino pin 11
 6 Enable            Arduino pin 10
 7 No connection   
 8 No connection   
 9 No connection   
 10 No connection   
 11 Data 4            Arduino pin 5
 12 Data 5            Arduino pin 4
 13 Data 6            Arduino pin 3
 14 Data 7            Arduino pin 2
 15 Backlight      + 5v Arduino pin
 16 Backlight GND GND Arduino pin*
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Western New York, USA
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I suggest that you disconnect everything and start over with this tutorial http://www.ladyada.net/learn/lcd/charlcd.html .

Don
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* LCD VEE to the potentiometer 10k

HD44780 lcds don't have a VEE signal.

--- bill
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HD44780 lcds don't have a VEE signal.
That would depend on the editor of the datasheet.  I have a JHD162A data sheet that does indeed have pin 3 labeled as VEE.

don
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As an outsider of electrical engineering, I didn't know these symbols until relatively recently, like a year or two ago. Vdd is drain's biasing voltage for an n-channel mosfet by default so represents positive supply. Vss is the bias voltage of the source and that is often grounded so stands for ground.
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Dr,
I believe Don's comment was sarcasm.
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I believe Don's comment was sarcasm.
Actually I removed most of the sarcasm before I posted.  The first sentence was something like this:
"That would depend on the editor of the datasheet, who was probably not an engineer."


Don
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My limited understanding of transistors stretch as far as VEE stands for emitter bias voltage of an NPN bipolar junction transistor and that is often tied to ground so VEE=ground. Then VCC is the bias voltage of the collector of that NPN BJT again and is tied to power (such as 5V). So is VEE,VCC vs. VSS,VDD between engineer and non-engineer or between older and newer names? I only know the meanings of these symbols but don't know what they imply like regional preference in the use of terms coke vs. soda vs. pop vs. soda pop?
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That pretty much agrees with what I remember.  When the two subscripts are the same (as in VCC) you are talking about a bias or supply voltage and when they are different (as in VCE) you are talking about a voltage between two terminals of the device, collector and emitter in this case.

The manufacturers of the various LCD modules appear to pick their subscripts somewhat at random, especially for the designation for pin 3.


Don
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Italy
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contrast still doesn't work connecting in both ways, i can wind the potentiometer how many times i want but nothing changes.
is it possible that Arduino UNO doesn't support JHD162A? On youtube and other tutorials on-line i only see Arduino Duemilanove working with that.
« Last Edit: February 27, 2012, 04:05:49 am by nicolino » Logged

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Provide a picture how you connect everything.
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is it possible that Arduino UNO doesn't support JHD162A?
No.

Do you have a voltmeter?  With the potentiometer properly connected you should be able to vary the voltage measured between Pin 3 and GND from 0 to 5 Volts.  The proper setting will typically be around 0.5 Volts. 

With many LCD modules you will get a usable display with Pin 3 connected to GND.  You could try that.


Don
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Have a look here (in french, as Jean Dujardin said, nobody is perfect) !

https://sites.google.com/site/arduinoiut/home/lcd20x4

Dr. L. Aldon
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Have a look here (in french, as Jean Dujardin said, nobody is perfect) !

Did I miss something.  That looks like most every other LCD tutorial that is out there.  Why point him there unless you suspect that the OP is French speaking (he didn't bother to fill in the 'location' information in his profile).

Be advised that many, if not most, LCDs require an external series dropping resistor for the backlight.  None is shown on the diagram included with that tutorial so I guess that your quote is applicable here.


Don
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