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Need help with my project ... Heating

Discussion in 'General Electronics Discussion' started by MrArduino, May 25, 2016.

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  1. MrArduino

    MrArduino

    1
    0
    May 25, 2016
    Hi,

    Please excuse me for lack of correct terminology etc, I am a complete noob at all this.

    I have recently invested in an Arduino to try to help me complete a college project, I basically need it to monitor the temperature of a surface and activate a heat element when it drops below 2 degrees celsius.

    So I have got the basic concept working. At present, the system checks the temperature ....if above 2 degrees celsius it goes to sleep for a set period of time before rechecking or if below 2 degrees celsius it activates an LED (I've used that because I haven't worked out the heating bit yet).

    So this is where I need the help:

    1. What can I use to heat a glass surface about 1 metre x 2 metre in size?
    2. How would I power it? It needs to be from a battery - as the item needs to be portable...is it possible to generate a decent amount of heat to actually heat the surface?

    I imagine that the main circuit will run off a 9V battery, which with a bit of tweaking should last a good length of time.
    I would then be in effect, activating a separate circuit powered by a more powerful rechargeable battery when heat is required.

    Would really welcome and thoughts / suggestions

    Thanks

    A
     
  2. Externet

    Externet

    762
    166
    Aug 24, 2009
    hevans1944 likes this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,617
    2,156
    Jun 21, 2012
    You have not provided enough information to even begin a design. Does the glass have to remain transparent when it is heated? How is it cooled to 2 C or below? How is such a large sheet of glass supported, and what is its orientation (vertical, horizontal, tilted) with respect to gravity? How thick is the glass? What is its composition? What is the specific heat of the glass? What is the mass of the glass? Will you monitor the average temperature of the whole surface, or only the temperature at a small spot on the surface? How will you do that?

    You need to use thermodynamics to determine the rate of heat loss from a glass surface of size 1m x 2m after specifying the environment the glass will be in. Will it be outside and cooled by the ambient air? Will there be air or wind flowing across the glass? Will the glass be insulated from its physical surroundings? If so, provide information on the thermal resistance between the glass and its environment. Can you explain how the glass will lose heat through convective and conductive processes? Can you estimate how fast the glass will lose heat? From this estimate, can you determine how many watts of electrical power you will need to maintain a temperature of 2 C?

    To electrically heat glass a transparent conductive film can be applied with electrical power supplied at opposite edges, or at multiple points around the outside edge. This is how aircraft cockpit windows are de-iced. You would need to have access to a large enough vacuum chamber to perform magnetron sputter deposition of a tin oxide or indium tin oxide film. There are also solution deposition methods, but these may involve toxic chemicals. Or you can blow warm air over the glass with a hair dryer or heat gun. Or you can mount a radiant heater element behind the glass and hope the glass absorbs enough infrared radiation to compensate for heat losses. Lots of ways to heat glass, depending on what your (unstated) objectives are.

    Just how portable do you think a 1m x 2m sheet of glass is going to be? Why does it need to be heated with energy stored in a battery? What size battery? A lead-acid automobile battery will provide a decent amount of power for several hours, depending on how often and how much power is needed. You could also place one or more batteries in a wheeled cart for transport. Radio amateurs will be doing this for next month's Field Day Operations.

    If you are powering "a separate circuit with a more powerful rechargeable battery when heat is required" why not power your control circuitry from the same source? Of what use is the control circuitry (presumably an Arduino and friends) if it isn't controlling a heater requiring a rechargeable battery?

    The Forum is looking forward to your answers to these questions... well, I am at least.
     
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