I'm trying to hunt down a cheap graphic display that can operate on a vehicle dashboard. Given the temperatures involved, it specificailly needs to operate in temp ranges from 0°C to 50°C. I know a couple models that allege to work in this range but I've had problems with dash-mounted equipment turning blue or black in the Texas sun. I'm looking for something with extended temperature range. With more emphasis on extreme heat.

I'm looking for sizes in the 96x64 to 320x240 range or very close. Backlit. Monochrome preferred. Basically anything simpler than a laptop-style display. Any sources?

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LCD's vary according to temperature - if you want to use one over an extended temperature range then you need to add a circuit that varies the contrast with temperature - but too much heat will still render the display useless.

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LCD's really aren't designed for that kind of heat, and most definitly not for direct exposure to sunlight at those temperatures. Most LCD's you'll find in a car are as best situated away from direct exposure to light as possible.

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Yeah, I've been noticing navigation displays tend to be mounted out the sun's reach while satellite radio devices use some different kind of display alltogether. I'm willing to have the LCD self-adjust or shut off when the temperature reaches any kind of +/- extreme but that won't cover me if this kind of heat can destroy them. If I can get one of those displays the satellite radio console use that would definately help but I don't know what technology that is or how much it costs per unit.

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The only other LCD like display tech I know of is OLED's. Organic light emitting diodes, they may be more temperature stable. Do a search on Digikey for OLED displays and look at the different manufactors, one of them may produce displays that can put up with the abuse.

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The satellite receiver might have a dot-matrix vacuum fluorescent or monochrome plasma-type display ... my car has 7-segment VFD's for both the clock and the stereo unit.
JB

*edit - did a search of that big on-line auction place for "dot-matrix" "plasma" "display" and found one which goes into a pinball machine. Probably bright orange ... about $150US. There's also a place in California which makes plasma and VFD matrix displays: http://www.babcockinc.com/

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Hi,

As people have suggested a VFD display would do the trick. Theres a couple of 200x64's on ebay (not 240x64) and some 122x32 going cheap. A 128x64 would be ideal though.

Again, an OLED would be nice as well, great contrast (2000:1?) and I know someone on ebay (US) that has a few going very cheap, I picked up a couple myself and they're easy to interface with a micro. Plus, they look the nuts

As for 'sources', Digikey and mouser carry OLED's and VFD's...altohugh the OSRAM OLED displays are pretty small (2.1" max). With all that said, PLED's/OLED's don't like direct sunlight much either, but they perform alot better than LCD's in that situation. There are extended temperature LCD's, which will work up to 70C, but thats ambient. The build up of heat in the display itself in sunlight would probably shorten its life a great deal. Have you considered making your own LED display? For segments, bargraphs, and shaped lightguides? Obviously not as purely configurable as a dot-matrix, but great readability and long life.

If you really want to go down the 'LCD' route, I'd suggest a few filters for the colour of your LCD, and some polarizers. They'll absorb a great deal of the light that isn't necessary for reading the display, before it gets to the LCD...and then theres always fans and coolers.

one simple idea, if you've got space, set up a couple of mirrors, so the display itself is embedded in the dash. Mirrors should scatter some of the light reflected back down the system, minimising the ammount shone on the LCD.

The last few idea's are a bit random, and probably not practical, but if you've got time, possibly worth a try. Very few forms of display can cope well in those conditions, with the exception of military grade displays.

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OLED displays can use the same transflective backing as LCD displays can. VFD's and LED's are COMPLETLY unreadable in daylight conditions.

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Hi,

I'm not sure if 'completely unreadable' is right. After all, the military wouldn't even touch LED displays if that was the case. Almost all car stereo's (not the flash TFT ones) use VFD displays. Granted, its not easily readable in daylight, but you can make out whats going on. Of course, you're right about the transflective bit. In fact, that might be better than reflective....because it will allow some of the light through the display, not all the way through, then reflect it all the way back.

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Call me uninformed but explain to me why an OLED display would have a transflective backing. LCDs need it because they polarize light that passes through them. The light can be sourced from the rear with a backlight or reflected from the front with a transflective backing.

OLEDs generate their own light and should not require a backing.

And saying that LED's and VFD's are not visible in daylight conditions is completely false. There are plenty of high intensity modules that are readable in direct sunlight even with sunglasses on.

 

Well don't I feel sheepish =)

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