Affect of -40C temperatures on a LCD display

[nobb123]

Hey.

I have a carpc and I am looking to get a new LCD screen because my current one does not operate in -40C temperatures. I was hoping someone more technical than me might be able to answer some questions I have on LCD screens and operating them in low temperatures. I am interested in this screen:

http://linitx.com/viewproduct.php?prodid=10949

Its minimum operating temperature is -20C, but I am wondering if I can operate it at even lower temperatures (and the possible negative effects). Some users have reported that their LCD screens (other models) have worked in even lower temperatures. What sort of negative effects do such low temperatures have on these screens? I have read that the CCFL backlights used in these screens have shorter lifespan if operated at such low temperatures. Can someone confirm? What about the actual LCD screen itself? Is there a possibility that the freezing of these liquid crystals might crack the screen (like frozen water cracking stone)?

How do car manufacturers with OEM LCD screens integrated into the vehicles deal with these temperature extremes?

 

[Danger]

I don't have a direct answer to your question, but an idea for a possible solution if you can't find a suitable screen. You should be able to install heating elements (such as used in windshields) behind the display inside the cover. I doubt that you'd be able to tap into the backlight supply because of the power requirement (still quite low), but you could run a secondary wire spliced into the main power source.

 

[nobb123]

Well...in my current monitor I did use a bunch of resistors (25 watts), but that is untested and I will have to wait until the winter. My current fold up monitor is a single DIN (the size of a standard car radio) but I don't know how efficient 25 watts worth of heaters will be at heating up that volume of space. I suspect it probably takes quite a bit of power to bring the temperature from -40C to 0C.

 

[mgb_phys]

The LCD screens in our equipement slow down considerably below about -10,-20, at -40 they don't work at all but we haven't had any damaged by freezing as the liquid layer is very thin.
These are simple calculator style dot-matrix displays so refresh speed is not very important. In the field we just put a chemical heat pad over them for a few minutes to warm them enough - fortunately these temperatures are rare enough we haven't bothered to make a heated version. But that should be possible.

 

[berkeman]

-40C is about -40F. Who is going to be looking at a screen at -40?

 

[mgb_phys]

Canadians!
We make laser scanners for surveying, the mining/oil sands businesses don't stop for a bit of snow.

 

[Danger]

it probably takes quite a bit of power to bring the temperature from -40C to 0C.

Ah, but you don't have to. You need raise it only to -20.

Who is going to be looking at a screen at -40?

Around here, that would be picnickers.

 

[nobb123]

The screen is used in a car, so I will be looking at it. I tried looking for schematics to maybe try to build a device which would turn on the heater when temperatures are below a certain temperature and turn it off after the set temperature is reached...but couldn't find any. Anyone have suggestions?

 

[Danger]

Do you mean the screen heater or the car heater? I'm thinking that the thermostat from a freezer would work if you change the switch from a Normally Closed to a Normally Open type.

 

[berkeman]

The screen is used in a car, so I will be looking at it.

If it's in a car, then you have ample power for a plasma display, which should have a lower operating temperature minumum. Have you looked at plasma displays instead?

 

[Danger]

Decent idea, Mr. B.

 

[nobb123]

The LCD screen is 7 inches and mounted in the dash. I think you are mistaken and thought this was for a motorhome or something. Besides...I don't think they make 7 inch plasma displays, but good idea though.

 

[Danger]

In that case, I would seriously recommend tossing the resistance heaters in there and running them from the vehicle battery (preferably an auxilliary deep-cycle one if you're going to be on for long time without starting the engine).