My LCD display has become dimmer.

I have purchased this LCD
http://www.dx.com/p/lcd-keypad-shield-for-arduino-duemilanove-lcd-1602-118059#.UzPpFie5FEI
I have had it connected and powered on a Arduino Uno for some months 24h/day. And I can see a clear dimming of the display occuring during the time. For now the display is barely readable. And yes I did use the pot to set max brightness.
Is this normal? Anyone else having experience with this particular display?

it seems that the LED of the LCD is nearly dead.
Most reasons for that: the resistor for the LED is to small or not present at all.

Depending on the colour of your led it needs a specific volt value - most works with V, but died later in case of "burn-out" :sleeping:

A.R.Ty:
it seems that the LED of the LCD is nearly dead.
Most reasons for that: the resistor for the LED is to small or not present at all.

Depending on the colour of your led it needs a specific volt value - most works with V, but died later in case of "burn-out" :sleeping:

The shield is supposed to be connected directly to the Arduino. So I would expect any needed resistor to be part of the design. Otherwise the product is not correctly designed.

The shield is supposed to be connected directly to the Arduino. So I would expect any needed resistor to be part of the design. Otherwise the product is not correctly designed.

Normally of course yes - but Shit happens 8)
You're not the 1st (and also not the last one) who gets an damaged board/display.

Or do you think its part of the "design" that the LED gets darker ? ]:slight_smile:

Now hang on a moment.

As so often happens, there seems to be some confusion here.

The LCD is illuminated by a white LED. Its brightness is readily visible at the right hand side of the display. This has absolutely nothing to do with the contrast setting, which is the potentiometer. So which is it? Is the amount of the light emitted by the white LED decreasing? Or is it just the same as ever, but the brightness of the text is reduced, which is a function of the contrast setting?

You need to measure the actual voltage on Vcc to ground on the Arduino. If this is substantially less than 5V, the LCD will not work properly. This can be due to failure of the USB protection circuitry in the computer if you are powering it from USB.

If the LED itself is waning, you need to check the voltage on pins 15 (+) and 16 (-) of the LCD module. Should be 4.7V or at least 4.5. The most likely failure here is the transistor circuit on the shield that switches the LED on. Very few LCD boards, and none of these shields, do not have the current limiting resistor (R8, "101" or 100 ohms and R9, zero ohms) for the LED on the LCD board itself.

Paul__B:
Now hang on a moment.

As so often happens, there seems to be some confusion here.

The LCD is illuminated by a white LED. Its brightness is readily visible at the right hand side of the display. This has absolutely nothing to do with the contrast setting, which is the potentiometer. So which is it? Is the amount of the light emitted by the white LED decreasing? Or is it just the same as ever, but the brightness of the text is reduced, which is a function of the contrast setting?

You need to measure the actual voltage on Vcc to ground on the Arduino. If this is substantially less than 5V, the LCD will not work properly. This can be due to failure of the USB protection circuitry in the computer if you are powering it from USB.

If the LED itself is waning, you need to check the voltage on pins 15 (+) and 16 (-) of the LCD module. Should be 4.7V or at least 4.5. The most likely failure here is the transistor circuit on the shield that switches the LED on. Very few LCD boards, and none of these shields, do not have the current limiting resistor (R8, "101" or 100 ohms and R9, zero ohms) for the LED on the LCD board itself.

I think that both the LED and TEXT has reduced light. Voltage on pin 15 is 5 V just like Vcc. I'm not powering from USB but from a DC adapter 9 V that can deliver 1.5 A.

I think we need a photograph. Perfectly focused, resolution 1024 by 768 maximum. Insert using the "Insert Image" icon just to the left of the blue "world."

Paul__B:
I think we need a photograph. Perfectly focused, resolution 1024 by 768 maximum. Insert using the “Insert Image” icon just to the left of the blue “world.”

After clicking Insert Image how do I place the actual image there? At any rate I have attached a photo in the post.

You can't place an image here, other that what you did (attaching it).
If you want to put the image in a post, instead of attaching it under the post, you need to have a place to upload the image to, like imageshack or photobucket.
Then, after uploading the image, you can point to that in your post, where it will appear.
But please use another picture that is sharp and actually shows what you can see on your screen.

I have the same shield, and i'm also one of the 76 reviewers of it.
This shield has this issue (click !) for sure.
You might have done some damage to your Arduino pin 10 that tries to control the brightness of the backlight.
You may want to check the status of pin 10, to ensure that is set to send 5 volts and not some PWM value (you would also need to set it as an output).
If you do send a PWM value to it, make it a value of 255 (full strength), after reading the link i posted a moment ago.
The picture does seem to show a dim LED, mine is quite bright.

MAS3:
But please use another picture that is sharp and actually shows what you can see on your screen.
You might have done some damage to your Arduino pin 10 that tries to control the brightness of the backlight.
You may want to check the status of pin 10, to ensure that is set to send 5 volts and not some PWM value (you would also need to set it as an output).
If you do send a PWM value to it, make it a value of 255 (full strength), after reading the link i posted a moment ago.
The picture does seem to show a dim LED, mine is quite bright.

I have problem getting the photos sharp. I attach a new photo showing the display. But I don’t think it makes justice to the issue. It’s really dimmer than what you get an impression from the photo. The characters are barely visible.
I don’t have a PWM pulse on pin 10 bot a steady 4.8 V. Checked with my oscilloscope.

have problem getting the photos sharp.

MAximum brightness of (best) light with all spectral colors (liek daylight) and, if you use macro or zoom, a stative of fixed stand is always the best