LCD Rear Solder Required?

Hi All,

I am trying to use this screen (http://www.newhavendisplay.com/specs/NHD-0216SZ-FSW-FBW.pdf) in 4-bit.

Backlight is lit, and I have a good 5V on Pin 2. Pin 3 is changing voltage when I adjust the 10k pot, but absolutely nothing changes on the screen itself. (For troubleshooting, all of the other pins are disconnected)

I've read some things about pins on the rear of certain LCDs requiring connection; since I cannot get a row of blocks on this screen, I'm assuming something with either logic or contrast is messed up.

Any advice on how to approach here? I hate thinking that this is a hardware issue, but nothing I do here shows any contrast on the screen at all and I therefore have no clue if logic is working.

Thanks!

Do you need to enable the display (pin 6)?

It's my understanding from all of the tutorials that the LCDs should show one row of squares to indicate that there is a logic communication.

How would I go about enabling the LCD outside of the example LCD scripts?

The LCD is blank, so hard to know anything from that.

Thanks!

Enable should just be a matter of putting that pin to ground.

Backlight is lit, and I have a good 5V on Pin 2. Pin 3 is changing voltage when I adjust the 10k pot, but absolutely nothing changes on the screen itself. (For troubleshooting, all of the other pins are disconnected)

You are on the right track. You should be able to see black/while squares with only pins 1,2,3 and 15,16 connected. Do you have ground on pin 1? Can you post a picture of your wiring and the solder joints on the lcd? What do you see if you ground pin 3 instead of using the pot?

Why do you mention "Rear Solder"?

Obviously the LCD will not work unless whatever header pins you are using, are properly soldered to it.

Here are some pictures; everything is soldered to screw terminals and proto boards.

Pin 1: 0V
Pin 2: 5V
Pin 3: Variable 0-5V and responsive when I turn the pot
Pin 15: 5V
Pin 16: 0V

I’m assuming the solders are all good.

I just grounded pin 3; same result as before. Strange since it actually was shifting the voltage on the LCD pin.

Thanks for any advice!

Any thoughts on this guys?

Thanks again for the help!

9035127cc6336789b32c3c722aa704f6f3a3ee7f.jpg e9f87d9238b9115aaf0780dfbe6c32bff4ae818d.jpg

So what are they supposed to tell us?

That everything is attached and soldered correctly? They were asked for, I provided.

This is the whole point; the LCD is seeing the correct voltages but does not appear to have logic communication. I'm trying to find out if there's any additional troubleshooting that I can do here, or if the screen is not functional.

Thanks

I think your connections look highly suspect, but I mean, I can't tell anything from the pictures they are at odd angles....

I don't see your arduino or your connections from the Arduino to the screen. you need at least six connections from the arduino to the screen, show your sketch and the connections.

Per this tutorial (Overview | Character LCDs | Adafruit Learning System), the screen should show a row of squares before anything is attached to the arduino.

I mentioned all of the pin voltages in a previous post; how can these all be correct if my connections are bad…?

Who cares? is having those voltages read as you expect helping you in solving this problem...

Per this tutorial (https://learn.adafruit.com/character-lcds), the screen should show a row of squares before anything is attached to the arduino.

Correct.

I mentioned all of the pin voltages in a previous post; how can these all be correct if my connections are bad..?

If the solder joints are indeed good and the voltage you see is getting from the wires in the terminal block to the actual gold pad of the lcd then you should see blocks. I believe that either you have a bad connection or a bad display. Your photos do not show the quality of the solder joints between the pins of the terminal block and the lcd pads. You might try resolder those connections.

The terminal block is not a frequent connection to the lcd displays. Most frequently there is an i2c backpack, or male pins soldered to the display for insertion into a breadboard, or wires soldered directly to the display. The solder quality of those joints is critical.

What did you mean about "rear solder"?

Hi
What sketch are you running on the arduino?

Can you please post a copy of your sketch, using code tags?
They are made with the </> icon in the reply Menu.
See section 7 http://forum.arduino.cc/index.php/topic,148850.0.html

Have you used a DMM to make sure your connections from the solder tags on the LCD are correctly made to the pins of the arduino controller?

Tom… :slight_smile:

Big goof on my end, thought this really is unclear in the manual.

All the solders were indeed good, the problem was that the pin numbers from left to right are 16,15,1,2,3,4,5,6,7,8,9,10,11,12,13,14. I figured it was 16-1!

The rear solder I was originally referring to is related to some threads I read here about adding solder to the J2 section on the actual read of the LCD PCB, behind the screen. It's my understanding that these may be used by the manufacturer to select input voltage, ect.

jgatvl: Big goof on my end, thought this really is unclear in the manual.

Guess we knew that. :grinning:

jgatvl: The rear solder I was originally referring to is related to some threads I read here about adding solder to the J2 section on the actual read of the LCD PCB, behind the screen. It's my understanding that these may be used by the manufacturer to select input voltage, ect.

They may indeed be - by the manufacturer. Nothing to do with anything you would want to fiddle with.

The 3.3 V versions of the display include a "charge pump" IC like the good ol' ICL7660, not because the logic IC requires 5 V, but because the LCD panel itself requires a contrast voltage of about 4.4 V. If in the 5 V version, that IC is not present (nor are the capacitors C1 and C2), then the power connections are jumpered over by a link, notably J1. But nothing here for you to meddle with.

jgatvl:
Hi All,

I am trying to use this screen (http://www.newhavendisplay.com/specs/NHD-0216SZ-FSW-FBW.pdf) in 4-bit.

Backlight is lit, and I have a good 5V on Pin 2. Pin 3 is changing voltage when I adjust the 10k pot, but absolutely nothing changes on the screen itself. (For troubleshooting, all of the other pins are disconnected)

I’ve read some things about pins on the rear of certain LCDs requiring connection; since I cannot get a row of blocks on this screen, I’m assuming something with either logic or contrast is messed up.

Any advice on how to approach here? I hate thinking that this is a hardware issue, but nothing I do here shows any contrast on the screen at all and I therefore have no clue if logic is working.

Thanks!

I’ve found that SOME LCD displays (Optrex, so far) require a NEGATIVE voltage on the Vee pin (about -3.3 volts). Simply tying Vee to ground will not give you a display (if yours is like the Optrex that needs a negative Vee).

To test if this is the problem, get two AA cells or a lithium coin cell (the 3.6 volt kind). Connect your AA cells in series to make a 3 volt battery (or use the coin cell) and connect the POSITIVE side to the LCD ground and connect the NEGATIVE side, through a 100 ohm resistor (just to be safe) to Vee.

You don’t even need to have the LCD connected to the Arduino… just give it power, ground and -3 volts Vee.

If it works, you will get one line of dark blocks on the display.

Then you can go on and connect it to the Arduino and see if it will display characters.

If it works… now what? Where do you get -3 volts?

Answer: From your Arduino!

(click pic for full size)
vee_generator.jpg

Use this circuit to generate about -3.5 volts DC which you can then run to the contrast pot of the LCD.