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Help me design my carputer to work in the cold (advice on building a heater)

  1. Apr 15, 2007 #1
    Help me design my "carputer" to work in the cold (advice on building a heater)

    Hello.

    You guys seem to be a knowledgeable bunch, so I thought maybe I'll post thing. My problem is that I custom built a computer to run in my car and I really need some help. I live in Calgary, Canada where in the winter, it can get down to -30C. The actual computer itself runs fine and I am not worried about that. However, I bought a motorized lcd touchscreen(k301 or mtsvo-sc), which does not work so well in the cold. The problem is that it has an electronic sensor which prevents the screen to open when the temperatures drop below -5C. The lights will just flash until the temperature has warmed up. I would like to force this screen to open in the winter. Its dissapointing to spend $400 canadian on a screen, but to have it not operational for 1/4th of the year due to weather problems.

    I have already tried taking apart the screen in an attempt to perhaps find the chip which does the temperature sensing, and maybe try to hack that. So far, no luck. Now maybe I am thinking maybe try to build a heater and I would like some tips, advice, whatever to help me get this working.

    I was thinking maybe using some small resistors and wiring them up as a heat source within the touchscreen. I got the idea from randomly finding a page where the guy built a "dew heater" for his telescope using resistors. Idealy, I would like to know where the temperature sensor is so that I can build the heater as close to it as possible for fast results, but I do not know where this temperature sensor is. So now maybe I am thinking about building a "sheet" of resistors to place in the bottom of this unit as a heat source. When folded up, my touchscreen is the size of a standard single DIN radio. How much wattage would you guys suggest to bring the temperature of this unit up from -30C to 0C. Just a rough estimate maybe. The heat probably wont be spread evenly, so dont assume this to be a thermodynamics question :wink:
    I'll probably also use ducttape around this whole heater sheet just to keep from having anything shorted out. So what should be the maximum power dissipated by each resistor, just to make sure the duct tape doesnt melt?

    I'm also concerned about condensation. I'd like the heaters to heat everythig up ASAP, but then I risk rapid condensation. Maybe some of you electrical engineers/circuit designers can give some suggestions.

    Are there any other considerations I should take into account? I'm open to all advice. Thanks!
     
  2. jcsd
  3. Apr 16, 2007 #2
    Interesting!

    I don't have any real solution to your problem, but I have a few comments and a ghetto suggestion. (It was fun to imagine though, lol)

    I'm thinking that maybe it isn't a sensor preventing the screen from working, but rather is hardware failure at those temperatures.

    You might need to construct a fan to blow hot air across the circuitry and then use a heating element of some sort. You have resisters in mind, but I'm not sure how hot the resisters could get before they melt or how fast they would heat up. Typically, traditional heating elements require a high amount of watts to work and even then they have to be extremely hot to heat the air around them. You may not have enough electrical power for this.

    Maybe a "thinking outside of the box" solution would work best. Perhaps you could cut out the bottom of a frying pan, flatten it out, put sides on it, then weld it to the bottom of a CPU cooler's heatsink. Build a box around the CPU cooler's heatsink to direct the flow directly across the monitor's circuitry and then on the other side of the monitor, direct the airflow out through a tube back to an intake hole above the CPU cooler's fan to supply it with the hot air (you'll probably need a fan to help move the air back to the CPU cooler's fan). You wouldn't want the box over the CPU cooler to be completely closed though, because it will strain the CPU cooler fan and kill it after a while. Then take a small propane torch to heat up the bottom of the frying pan material below the heatsink, closing it in with more frying pan material, with a high heat insulator around the whole thing. There could be a heat sensor inside where the CPU cooling fan is to shut off the burner if it gets too hot.

    Just an idea.

    I'd look into "microheaters" on google if you want to go with a more conventional approach and are able to somehow supply the wattage necessary to feed these power hungry devices. (you'd still have to custom build the air flow system though)
     
    Last edited: Apr 16, 2007
  4. Apr 16, 2007 #3
    Nope its definately not a physical hardware failure. I know there is a electronic temperature sensor 100%. This is because the unit will beep when you try to open it in the cold. The front lights also flash until the temperature is warm enough, then it will just be lit steadily.

    I have already tried building a blower type heater, but it was too bulky and could only blow on the unit from the outside (very inefficient). This heater was about 100 watts and barely made a difference. I would like to make a blower type system on the inside of the unit, but there is not much room to work with as I am restricted to a height limitation of about 5 cm. But I will definately try to maybe somehow build a small air flow system inside the unit.

    I probably wont be attempting this until my finals are over (must study), so keep the suggestions coming!
     
  5. Apr 16, 2007 #4
    The beeping lights could be indicating hardware failure. Just because the LED's are getting power and functioning doesn't mean there isn't hardware failure in another part of the monitor.

    I got it!

    Cut a hole in the side of the monitor, attach a propane burner and turn the burner on! FRY CIRCUITS, FRY!

    hmm, ok, maybe not, lol.

    Maybe you should use a Pentium 4 extreme, then just route the exhaust from the computer to the monitor, they run hot like furnaces!

    Or.. Maybe you can just hug the monitor. Give it lots of love and body heat and it'll work for you.

    Ok, I'm done. lol
     
  6. Apr 17, 2007 #5

    FredGarvin

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    In gardening, there are items known as propagation mats. They are thin, electrical resistance heaters that are placed under seedling trays to provide a constant source of bottom heat. These help new seedlings grow over the winter months. They're not terribly expensive and they are meant to be used continuously. One may provide enough heat to keep you in the clear. Just a thought.

    http://www.greenhousemegastore.com/products.asp?dept=1101
     
  7. Apr 17, 2007 #6

    NoTime

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    Don't close it?
    That way you don't need to unlock it.

    I suspect that the reason it does lock is because it simply isn't going to work that cold.
     
  8. Apr 17, 2007 #7

    chroot

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    Please don't go reverse-engineering your LCD panel -- you will not make it work in freezing conditions. It doesn't matter whether or not you manage to get the cover open; the LCD itself will not work properly at sub-freezing temperatures, and there's nothing you can do to "hack it."

    You might want to consider a strip heating element, like this one:

    http://www.amazon.com/Orion-Dew-Zapper-8-Schmidt-Cassegrain/dp/B0000XMUB4

    You could wire up a small switch to power the strip. If you're handy, you should be able to buy a small thermostat from a distributor like Digi-Key, and wire it up to automatically heat your LCD panel to operating temperature.

    - Warren
     
  9. Apr 18, 2007 #8
    I'm willing to bet that the "dew zapper" type devices aren't nearly big or strong enough for what he needs.
     
  10. Apr 18, 2007 #9

    chroot

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    Having used one many times, and held one in my hand many times, I can guarantee you they're more than adequate for the task. They're normally driven by some kind of PWM controller. When they're plugged directly into a constant 12V source, they'll get hot enough that they cannot be touched.

    I wouldn't have recommended the product if I was not sure it would work.

    - Warren
     
  11. Apr 18, 2007 #10
    But is it hot enough to be used like a small space heater? He might need to run air over it and through the monitor's circuits.
     
  12. Apr 18, 2007 #11

    chroot

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    If he can attach the heating element to a major piece of metal in the case of the LCD, it's likely that he could heat the entire device up to operating temperature in just a couple of minutes -- certainly by the time the engine is warmed up.

    If the application needs airflow, you can also buy 12 VCD "hair dryers" from astronomy suppliers like Orion. You could probably take the hair dryer out of its plastic enclosure and mount it directly behind the LCD unit, again with a switch or thermostat to turn it on and off.

    Depending upon how the unit is mounted, what's behind it, and how it's packaged, one of these two approaches should be fine.

    BTW, the electrical system in any car should be able to handle > 300 W, depending upon how the cigarette lighter circuit is wired and fused. Just make sure the engine is running, and you're not pulling this kind of current from the battery -- batteries don't work that well in the cold. If you decide you need a LOT of power, you can run your own power line from the battery (with an appropriately-rated inline fuse). It's not a difficult job and you could easily get > 2000 W delivered to the dash.

    - Warren
     
    Last edited: Apr 18, 2007
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