LCD not working

Other Hardware General Electronics
1

I'm having problems getting a 16x2 LCD display to work. (The part no is 1602gd1622y)

Following to the Adafruit LCD tutorial, I've hooked up +5v and Gnd from the Arduino, and a 10k pot for the contrast.
(The display does not have a backlight.)

I'm confident of my soldering for the header pins and I have checked the voltages on the header pins relative to the Arduino and the pot, and they all make sense.

Looking at the back of the Display there are what I assume are the SMD equivalent of jumpers - small exposed contacts that could be shorted with a dot of solder.

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From what I can see J3 is connected to the -ve pin on the header, and J5 is connected to +ve pin.
I can find no mention on the datasheet of these jumpers(?) but do they need to be soldered to get the display to work?

2

Use your ohm meter to see if these are actual breaks in the traces.
If they are, you will have to complete the circuit pathways.

It is best to buy this kind of stuff from reputable dealers like Adafruit/Sparkfun etc.

3

I don't see how we can draw any conclusions about your situation without seeing the code you are running.
In addition, you have not posted any documentation or pinout for the the black header connector or how you wired it or how you configured it in the software. We have no idea what (if any ) experience you have with LCDs. We also don't know if you know what an LCD Constructor is or how that relates to how you wire it up. Please post all this information.
consult ypour documentation before doing anything.

The very fact that you are posting here instead of the Adafruit Tech Support Forum is cause for concern. Once you open a ticket , they will answer them in the order received. Don't solder anything until you consult the manual on their website.

4

Sometimes you have to guess :confused: because of the abundance of information, NOT.

5

Did you click on the Datasheet link ?

It would not make sense to sell an LCD that requires soldering those jumpers. They must be for non standard configurations.

6

I do like the look of those pads.

7

raschemmel:
I don't see how we can draw any conclusions about your situation without seeing the code you are running.

As I understand it, I should be able to see active pixles on the LCD with just the connections mentioned in my original post, if the contrast is adjusted. This is not a code dependent problem (which is why I posted it in the Gerenal Electronics forum, though to be fair, with hindsight, I should probably have posted in the LCD forum. My bad.)

raschemmel:
you have not posted any documentation or pinout for the the black header connector

As I understand it, the header pin configuration is standard for 16x2 LCD displays that are compatible with the Arduino.

raschemmel:
or how you wired it

Black : Gnd
Red : +ve
(Both as per the legend in the photograph.)
Brown from the wiper on the pot. Sorry, I assumed that was obvious and wouldn't need explanation.

raschemmel:
or how you configured it in the software.

This is not software dependent.

raschemmel:
We have no idea what (if any ) experience you have with LCDs.

More than enough to a) know that it's not working, b) it's not a code dependent problem, c) it could well be a power issure related to the jumpers. Which is why I asked the question about the jumpers.

raschemmel:
We also don't know if you know what an LCD Constructor is or how that relates to how you wire it up.

Yes I do, and this is not software dependent.
As you'll see from the original post and the photo in it, there are only power and contrast control going to the board and how those are wired up are not related in any way whatsoever to constructors, as this is not software dependent.

raschemmel:
consult ypour documentation before doing anything.

Having mentioned the datasheet in my original post I thought it would be obvious that I had alredy done that.

raschemmel:
The very fact that you are posting here instead of the Adafruit Tech Support Forum is cause for concern.

That's a fair point. I just thought someone round here might have some pertinent input. But please don't be concerned.

raschemmel:
Don't solder anything until you consult the manual on their website.

a) Seeing as the display was sold without any headers, I figured soldering some on was pretty imporant.
b) I had RTFM first.
c) Header pins are just header pins. It's kind of difficult to get the connections wrong!

raschemmel:
Did you click on the Datasheet link ?

Having mentioned the datasheet in my original post I thought it would be obvious that I had alredy done that.

raschemmel:
It would not make sense to sell an LCD that requires soldering those jumpers. They must be for non standard configurations.

You might find it interesting to read the Adafruit tutorial I linked to. They seem to think it is perfectly standard.

raschemmel:
Please post all this information.

Did I miss anything?

8

LarryD:
Use your ohm meter to see if these are actual breaks in the traces.
If they are, you will have to complete the circuit pathways.

Surely that doesn't account for the possiblity that they could act as by-pass jumpers?

LarryD:
It is best to buy this kind of stuff from reputable dealers like Adafruit/Sparkfun etc.

(I'm not concerned about Rapid as a supplier. They're UK based and have been around a lot longer than the Arduino.)

9

LarryD:
I do like the look of those pads.

So do I.
I was hoping someone had some experience of them before I tained them wth tin & lead.

10

Let's say the black wire pin goes to the center of the nearest (nice looking) pad.
Is the inside trace to outside trace zero ohms?
If it is open, does that pin go anywhere else?

11

Assuming that you have already run the pot to max and min and still see no pixels (implied), I say short the jumpers and give it a shot. Short connect to power with the pot at mid-way isn't likely to doo much, if any, damage. Besides, what's the worst that can happen? You make smoke? it ain't like you're blowing up the house.....

12

You shouldn't smoke.

13

Silly question but are you sure you are on pins 1, 2 & 3 and not 14, 15, & 16 ?
It is not uncommon to see polarity markings on the backlight Led pins (15 & 16). It is , however, uncommon to see them on the LCD power pins (1 & 2). If your pot is connected to pin-14;it as not going to work.

14

I do like the look of those pads.

To me, they look like they'd be difficult to clean up if you needed to unsolder them.

15

Solder wick with flux to the rescue.

16

Take a close look at this photo and look at the pin numbers at the end of the connector at the bottom left and then look at the photo you posted in your original post and reread Reply#12.

If you were on pins 1, 2, & 3, you would be all the way at the end of the display and not near the middle.

That's what it looks like to me.

17

raschemmel:
Silly question but are you sure you are on pins 1, 2 & 3 and not 14, 15, & 16 ?

Not such a silly question!
Without numbers on the board and a +ve & -ve in the right place I just assumed.
Well that's embarassing!!!!

Thanks for the help.

18

So your good now?

BTW, you might want to undo anything you did to those jumpers.

19

I didn't do anything to them. Thankfully.

20

Incidently, the give-away clue was the polarity markings on the PCB. Like I said, it is common to see that for the backlight power and rare to see it for the LCD power. (why I don't know). The rest was just
finding a photo to confirm it.