I'm using a standard 1602 LCD in my project and it is on 24x7. I was just wondering how long these things last. I know on printers these things lasts pretty much forever, but I think they turn off the backlight. I don't turn off the backlight on mine. I imagine the backlight is probably the first thing to go. If you have used one continuously for a while, how long has it been running?
thanks
Most of these LCDs use LED backlights, which means they can last very long periods of time even at 24x7 operation.
Some LCDs have built-in current limiting resistors for the backlight designed to make the backlight work reliably for long periods of time. If your LCD doesn't have current limiting resistors for the backlight you should add those to make it work properly.
The LCD itself, as long as it is ran within specs should last "forever" (way longer than it's useful lifespan).
I agree with TheCoolest.
Many LEDs are specified to run at 20mA, but I'm not sure what LED is used in these displays -- it could be rated for only 10mA. I run mine at 10mA using a current-limiting resistor and it seems plenty bright so I'd say 5-10mA is reasonable.
If the display manufacturer used a good quality LED, they are usually specified for a lifetime of 50,000 hours so 5 years or so lit 24x7 at full power. Reducing the power below max makes them last even longer.
On the other hand, if the manufacturer grabbed bottom-of-the-barrel junk, the LED might dim early, after only a year or so.
In the "bad old days", the illuminant for the display was an Electroluminescent ("EL") panel with a limited lifetime and progressive loss of brightness, so they used "screen saver" techniques, as much for the illuminant as for the display proper.
Now with LEDs, they are substantially more efficient, far simpler (the EL required a high frequency AC driver of considerable voltage) and - more durable. I do wonder how long the current LEDs, particularly white ones which use similar phosphors to a fluorescent lamp, will last but it seems they are doing pretty well so far.
In the early days, LCDs only lasted a few years - presumably they are now more durable.
forever it is then!!
I use an I2C module with it, so the backlight driver is in that I2C module (it has a transistor+resistor). It can't be too much current, as I power it from +5v pin of mega board. The I2C module chip is rated for 100khz, but I run it at 400khz using a custom i2c library I got from my quadcopter project and its been running for at least a couple weeks i2c error free. At 400khz, I timed the lcd update takes approximately 1/3 the time using the Wire library.