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Serial LCD for low temps?! — Parallax Forums

Serial LCD for low temps?!

steve_bsteve_b Posts: 1,563
edited 2008-01-22 01:22 in General Discussion
Hi folks,

I've got one of the standard parallel LCD displays with a Seetron Seral/Parallel "Backpack"....great...works!!

I was playing in the car today with a GPS set up and noticed the LCD screen dim right out on me. It was COOLLLDDD (it is Canada!).
Anyhow, it came back after it warmed up (hoped I hadn't broken any of the 'cells' by freezing them).

So, I now can't use this for my handheld gps project.....

Any recommendations for a display for "cooler" temps?

Cheers

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<FONT>Steve



What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
Lee Travino after the second time being hit by lightning!

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-01-21 01:17
    LCD displays in general don't work well when they're cold. They rely on cholesterol-like crystals that are in a liquid-like state and move under the influence of an electrical field. When they're cold, their movement slows down or stops (if it's cold enough).

    For low temperatures, LEDs or vacuum fluorescent displays are better. When LCDs have to be used (like for large panels), heaters and insulation can be built-in.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-01-21 05:35
    Steve,

    There are plenty of extended temperature range LCD Modules available…Most require negative voltage on the contrast input in order to achieve that. I doubt I still have them, but B.G. Micro had some which is where I got mine last time. Otherwise, I would say LED of VFD if power wasn’t a concern. It sounds like your project is supposed to be portable? If so, LED and VFD displays can eat batteries up. Take care.

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    Chris Savage
    Parallax Tech Support
  • steve_bsteve_b Posts: 1,563
    edited 2008-01-21 13:24
    Thanks guys....I did purchase a VFD but haven't implemented it yet.

    I have some code streamlining to make it more power efficient (only writing to the SDlogger when ram is nearfull instead of every message).

    It is a portable unit for geocaching....so maybe part for car but then a hike at some point. Ah well, guess if the display goes wonky I'll have to go buy that nice Garmin I've had my eye on! [noparse];)[/noparse]

    So my excuse to the fiance will be (anyone ever notice how fiance is awefully close to finance....hmmm): " Due to a seasonal atmospheric loss of Kelvins, the cholesterene molecules embedded in the matrix of the display have fallen in to a crystalene form thereby rendering the display useless....can I please go buy a new gps....!!"

    hehe

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    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-01-21 15:01
    Steve,

    You may find the VFD consumes at least twice if not more current than the LCD Display. I would definitely check current consumption since this is a battery powered device. Providing a negative voltage for an extended temp LCD isn’t too difficult. If you decide to stick with it I could offer some tips. Take care.

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    Chris Savage
    Parallax Tech Support
  • steve_bsteve_b Posts: 1,563
    edited 2008-01-21 17:54
    Thanks Chris,

    I'll look and see what I'm after! Have noticed that the LCD is hard to see in daylight (common problem with consumer GPS units) and suspect I'd need a backlight. But if the consumption there comes close, or equals, the VFD, I might go with IT.

    Will connect it up and see how it does....of course, what I ultimately want is a graphical one (put a little compass rose on it)....

    Babysteps first though....

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-01-22 01:22
    Steve,

    I wonder what type of display you are using. LCD Displays cannot be beat for daylight visibility. Transreflective types rely on the light to see the display. A backlight wouldn’t even be noticed in the daylight. Do you have a part number for the one you’re using?

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    Chris Savage
    Parallax Tech Support
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