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?
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.
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."
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?
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.
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.
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.
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.
I cannot control the contrast with the blue potentiometer provided on the i2c to parallel bus converter which I soldered onto the back of LCD
Tried temporarily shorting pin3 (Vee) of the JHD204A LCD with
a)pin1 (Vss)-ve - nothing happens & the display contrast remains the same
b)pin2 (Vcc)+ve - the whole unit with the Arduino switches off due to short-circuit
It seems the JHD LCD manufacturer has disabled contrast control through Vee pin.
Checked the datasheet of JHD 204A. The manufacturer http://www.china-lcd.com/product_list.asp has disabled contrast control by giving a fixed internal resistance 'RLCD' at the Vee pin.
JHD204A Datasheet - connection:
I believe the exposed Vee pin is a parallel connection to Vss (-ve) pin which explains the 'short circuit'-ing if Vee is connected to Vcc(+ve).
penjoseph:
It seems the JHD LCD manufacturer has disabled contrast control through Vee pin.
penjoseph:
Checked the datasheet of JHD 204A. The manufacturer http://www.china-lcd.com/product_list.asp has disabled contrast control by giving a fixed internal resistance 'RLCD' at the Vee pin.
Excellent idea! That would prevent any problems regarding the contrast. Your photograph demonstrates it is already set perfectly, so there is no need whatsoever to adjust it. However the thing is, the schematic you posted is in fact, not that of the LCD, but of a suggested manner of connecting it to a microprocessor, so we are none the wiser.
I do hope you are not confusing the matter of contrast, with backlight brightness?
nicolino:
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
Many newer LCD displays require a few volts NEGATIVE on the VEE (contrast) pin to work. The typical contrast pot across 5v and ground no longer works.
To test if this is the case, take two ordinary alkaline cells ("batteries") in series to make a 3 volt supply. Then connect the positive end to Arduino ground and the negative end to the LCD VEE pin through a 100 ohm protective resistor.
If the display begins to work, you've found the problem. The contrast may be too low or too high, but the -3 volt test will at least prove to you if you have this problem.
So, now what? You need a negative voltage supply. No problem. See the attached circuit. Note that you can adjust the negative voltage output of this circuit by changing the analogWrite() value sent. Only 0 through 127 works, however, because 128 through 255 are the same waveform (as far as the negative generator circuit is concerned).
