Hello World LCD issues.

Other Hardware Displays
1

Hi there,

I am quite new to Arduino and have made an attempt at the Hello World tutorial, and have used the sketch and followed all the steps as found here.

I have plugged in and the LCD will illuminate, no problem. I then uploaded my sketch to the board, only to find it has no effect on the LCD whatsoever. The LCD continues to show a blank screen with no text, and when adjusting the 10k pot I am getting no change in the LCD, despite taking a multimeter reading over pins 3 (V0-contrast) and 1 (VSS-Ground) and getting good, variable readings between ~4.95V and ~0V depending on the position of the pot, so I have ruled that out as an issue.

I have rechecked my wiring numerous times and have changed all wires out once.

I am starting to feel as though I have a faulty LCD screen, but as I am new to this I may also quite possibly be missing something that I am hoping someone here can pull me up on.

All these parts (board included) are part of this kit I recently purchased (if you were wondering about the hardware).

I have also included pictures of my set up below.

Image 1

Image 2

Image 3

Image 4

Thanks in advance,
Tim

2

OK, two things to start:

  • Those Chinese jumper leads may be faulty. Test all of them by using each (in pairs) to make the connection to the LED on the display.
  • The effect of the contrast control cannot be nothing (unless the display is initialising but going no further). With no connections other than pins 1, 2, 3, 15 and 16, the contrast control when moved towards ground (and it only operates in the lower tenth of its travel) should display of "blocks" on the first line only. If it does not do that, then you cannot proceed.
3

Thanks for the quick response, Paul.

Paul__B:
OK, two things to start:

  • Those Chinese jumper leads may be faulty. Test all of them by using each (in pairs) to make the connection to the LED on the display.

Fair point. I took them all out and tested as you said. They seem to all be functioning well. I wish the solution was that easy!

Paul__B:

  • The effect of the contrast control cannot be nothing (unless the display is initialising but going no further). With no connections other than pins 1, 2, 3, 15 and 16, the contrast control when moved towards ground (and it only operates in the lower tenth of its travel) should display of "blocks" on the first line only. If it does not do that, then you cannot proceed.

It is beginning to seem quite likely that it cannot pass (or even reach) initialisation, as I have removed all jumpers and connected up 1, 2, 3, 15, and 16, to the LCD, and power to the pot, and cycling through the full extent of the pot's range, and the contrast control's effect is still absolutely nothing. See here for an image of the re-test setup.

I have not seen any life from a single pixel on this display since I started attempting to use it. So far the only life I have seen from this display has been the backlight.

Would you say then that I can't proceed with this display and should look into a replacement?

4

Well, you certainly need to achieve the row of "blocks" before you can proceed any further.

The red PCB fascinates me. Can you explain where you obtained the module? Some unusual modules require a negative contrast voltage (which since the contrast voltage is actually between "Vo" - pin 3 and Vcc, means they require more than 5 V) so you might just try connecting the positive of a 9V battery to the +5 V and the negative (thus, -4 V) to the terminal of your potentiometer previously connected to ground.

I have to chuckle when you say "cycling through the full extent of the pot's range". The "standard" manner of connecting the pot is actually rather odd as the useful range is never more than the lower sixth. It would in fact be more correct to connect a 1k pot as a variable resistor between Vo and ground with no connection to Vcc.

5

From the last picture - you have backlight and have tested contrast.

If you apply full power to contrast as you already did and full power to LCD you should get a full display across the first line - just full 5x8 characters. It has been awhile since I installed mine - the ground for back-light and for LCD MAY not be common, check that to make sure.

You do not need any data pins hooked-up to test this.

The LCD controller runs "power-up" test and outputs the line if all is OK.
If not - reinvest in new LCD, they are known ( mine did) to go bad.

6

If you apply full power to contrast ...

Surely you mean minimum power (as in close to zero volts).
Your contrast pin should be near zero volts with respect to GND or near maximum voltage with respect to Vcc (which is how it is specified). Power has nothing to do with it.

the ground for back-light and for LCD MAY not be common, check that to make sure.

Why? The two, LCD and backlight, are totally separate devices and there is no need for their grounds to be connected.

The LCD controller runs "power-up" test and outputs the line if all is OK.

I have never seen any documentation that mentions any kind of power-up test nor any documentation that explicitly says that this single line of blocks will appear when the device is working properly.

The reason that a single line of blocks appears under these conditions is most likely tied to the fact that the 'Internal Reset Circuit' initializes the controller in the 1-line display mode.

If not - reinvest in new LCD, they are known ( mine did) to go bad.

I wouldn't do this yet. I would check out the possible need for a negative voltage on pin 3 as Paul mentioned above.

Don

7

The red PCB fascinates me. Can you explain where you obtained the module?

From the OP's first post he references the Sparkfun inventors kit. I have the same kit and the red circuit board lcd. It's actually a very pleasing lcd in that it has white characters on a black background instead of the white on blue.

Mine runs with a standard pot set up and not negative voltage. I would doubt that SparkFun has changed the lcd in a beginners kit to one requiring negative voltage.

It may be the photo, but I don't like the look of the jumper coming from the pot to pin 3. For trouble shooting, I'd eliminate the pot and the wiring. Just run the 330 ohm resistor in the kit from pin 3 to ground, and you should see some blocks. Grounding the pin should light them all up white.

8

cattledog:
From the OP's first post he references the Sparkfun inventors kit.

OK. Clearly not concentrating! :roll_eyes:

9

Are you sure you do not have it wired backwards?
Pin 16 is usually at the edge and pin 1 is in center.
Backlight ON is no indicator you got it wired right, the ground pins are 1 and 16 , so the way you got it wired it would turn the back light on , but from wrong pins.
Move blue wire from pin 14 to pin 3 - check mate !

10

Pin 16 is usually at the edge and pin 1 is in center.

Not on any 16x2 that I have.

11

Pin 16 is usually at the edge and pin 1 is in center.

Where do you come up with this stuff?

Don

12

Paul__B:
so you might just try connecting the positive of a 9V battery to the +5 V and the negative (thus, -4 V) to the terminal of your potentiometer previously connected to ground.

Ok, I will give this a try later today when I'm back home and let you know how it goes.

cattledog:
From the OP's first post he references the Sparkfun inventors kit. I have the same kit and the red circuit board lcd.
Mine runs with a standard pot set up and not negative voltage. I would doubt that SparkFun has changed the lcd in a beginners kit to one requiring negative voltage./

Ok, interesting. Guess this this is another point in the 'faulty screen' column. I think I will still try the negative voltage option just to exhaust all possibilities though, thanks.

floresta:
Your contrast pin should be near zero volts with respect to GND or near maximum voltage with respect to Vcc (which is how it is specified). Power has nothing to do with it.

I have tried grounding the contrast pin, putting 5V to the contrast pin, and everything in between (through use of the pot, and observing the voltage changes using a multimeter). And as stated there has been absolutely zero change to the display, not a single pixel has so much as flickered.

cattledog:
It may be the photo, but I don't like the look of the jumper coming from the pot to pin 3. For trouble shooting, I'd eliminate the pot and the wiring. Just run the 330 ohm resistor in the kit from pin 3 to ground, and you should see some blocks. Grounding the pin should light them all up white.

Thanks for the idea. I tried that option (see image of this test here), and saw no change to previous outcomes, blank screen with only backlights, no pixel activity.

Vaclav:
Are you sure you do not have it wired backwards?
Pin 16 is usually at the edge and pin 1 is in center.
Backlight ON is no indicator you got it wired right, the ground pins are 1 and 16 , so the way you got it wired it would turn the back light on , but from wrong pins.
Move blue wire from pin 14 to pin 3 - check mate !

I also tried this, with no change to previous outcomes.

Thanks to all for your ideas, please keep suggesting! Even if they are to give up and request a replacement.

13

I also tried this, with no change to previous outcomes.

Didn't you read replies #9 and #10?

Don

14

Thanks to all for your ideas, please keep suggesting!

Disconnect everything.

Reconnect the power, contrast, and backlight components (those going to pins 1, 2, 3, 15, and 16).

Adjust the contrast potentiometer from one end to the other and you should see a row of 'boxes' when the potentiometer is near the end that puts a low voltage (with respect to GND) on pin 3.

If that doesn't work then use a voltmeter to make sure the potentiometer is actually varying the voltage at pin 3.

If you don't have a voltmeter then disconnect the potentiometer and connect pin 3 to GND.

Don

15

floresta:
Disconnect everything.

Reconnect the power, contrast, and backlight components (those going to pins 1, 2, 3, 15, and 16).

Adjust the contrast potentiometer from one end to the other and you should see a row of 'boxes' when the potentiometer is near the end that puts a low voltage (with respect to GND) on pin 3.

If that doesn't work then use a voltmeter to make sure the potentiometer is actually varying the voltage at pin 3.

If you don't have a voltmeter then disconnect the potentiometer and connect pin 3 to GND.

Don

Thanks for the suggestion.

I have done as you said and unplugged everything and reconnected power, contrast and backlight to 1, 2, 3, 15, & 16. And the potentiometer has been adjusted slowly from its minimum to maximum.

As before, there has been NO change to what has happened, not a single pixel has so much as flickered, let alone a line of boxes appearing.
Also as stated in the OP, I have taken voltmeter readings of the pot with respect to ground and and am getting good variable readings between 0V-4.95V.

For the sake of it I also connected pin 3 to ground, with no change.

16

You have said that you have changed your wires as part of your toubleshooting. In my experience, the breadboards, as well as the wires, can be defective. Try plugging the lcd into row b on the breadboard and moving the wire connections from e to d or c. You could also try swapping things around to the fghij side.

17

cattledog:
You have said that you have changed your wires as part of your toubleshooting. In my experience, the breadboards, as well as the wires, can be defective. Try plugging the lcd into row b on the breadboard and moving the wire connections from e to d or c. You could also try swapping things around to the fghij side.

Thanks for the idea, it did cross my mind earlier today. I'll give it a shot soon when I'm home.

Cheers

18

timmeh22:
Thanks for the idea, it did cross my mind earlier today. I'll give it a shot soon when I'm home.

I was hopeful and gave it a shot, but unfortunately, still no change.

UPDATE:

I started mucking around and swapped Pin 1 and Pin 2 (so swapped 5V into pin 1, GND to pin 2) and the screen looked darker. I then twisted the pot knob to find that the last tenth of its range resulted in a very slight drop in screen brightness. Then twisting back the other way, when reaching the other extreme of the pot's available rotation, a few of the pixels on both rows, probably about 3 "blocks" in from the RHS end flickered for approx 1 sec and then faded away. The whole thing seemed really strange, and is hard to describe.

It is also hard to replicate, maybe it is worth me recording it on video happening to explain in better detail.

Does this make sense to anyone here, or has anyone heard/seen a similar thing happen?

19

timmeh22:
I started mucking around and swapped Pin 1 and Pin 2 (so swapped 5V into pin 1, GND to pin 2) and the screen looked darker.

:astonished: :astonished: Unbelievably bad idea! :astonished: :astonished:

Fortunately, Vaclav's advice was by comparison, fairly harmless.

Assuming you have not now managed to destroy your display, have you actually tried my suggestion of the (adjustable) negative voltage on Vo?

20

Paul__B:
:astonished: :astonished: Unbelievably bad idea! :astonished: :astonished:

Fortunately, Vaclav's advice was by comparison, fairly harmless.

Assuming you have not now managed to destroy your display, have you actually tried my suggestion of the (adjustable) negative voltage on Vo?

I tried your suggestion and probably two-thirds of the pixels illuminated and the pot seemed to function as I expected, allowing contrast adjustment in the last small part of its rotation.
When at max contrast, the pixels seemed to fade toward the LHS of the screen (assuming pin-side as top) to nothing. See image below.

Image

From this information, what does this determine with respect to completing this tutorial and getting the LCD working?

The screen came with the kit, and the tutorial is designed around using it. Why is my situation any different to the tutorial, any ideas?