Advice on first build, temperature regulator

Discussion in 'The Projects Forum' started by STL, Nov 12, 2012.

  1. STL

    Thread Starter New Member

    Nov 12, 2012
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    Hello everyone... I want to start a temperature control project... I searched the forum and found one other related post, but it didn't really help me in my question... I have never done an electronic project before, but I'm certain that I can pull it off...

    I was wondering though if you all could give me some advice on the materials that I need to purchase, in order to put this project together...

    So this controller that I'm wanting to build, would work like this, it displays the temperature, you set whether you want it to heat or cool, set a desired temperature, and set a temperature buffer amount. When the temperature crosses the threshold, it provides power to the 120VAC electrical outlet.

    So I was thinking about starting off with an Arduino Leonardo board and Temperature Sensor - Waterproof (DS18B20)

    That's about all I got so far though... I'm not sure what you would call a component that I could use to turn on and off the power to a 120VAC electrical outlet

    Thank you in advance for your time.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,436
    3,360
    For a first project, you are in danger of getting to deep waters in more ways than one.
    It is better to start with something simpler so that you do not become frustrated and discouraged.

    To begin, when designing a temperature controller, there is a lot more to it than just setting a temperature and turning power on and off. We call this bang-bang control and this is what your house furnace thermostat does.

    For a smoother and more elegant control, you need to know a bit more about thermal capacity, heat loss and gain, power and time constants. A proportional control can be designed but this would be too complicated for a first project.

    Next, we are getting into controlling 120VAC directly with either a mechanical relay, solid-state relay or a triac. Here we would be treading on questionable ground because this forum has rules which are spelled out in the Terms of Service which you can find at the bottom of this page.

    Finally, if you are now starting out learning to program a microcontroller such as the Arduino, there are learning steps to climb.

    For a first project, I always suggest something such as a digital clock or digital thermometer. You want to stay clear of 120VAC for now.
     
  3. debe

    Well-Known Member

    Sep 21, 2010
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    184
    These days its hardly worth building one, they are avalable from Ebay for around $25. I use these for fridges but are programable for just about any aplication.
     
  4. STL

    Thread Starter New Member

    Nov 12, 2012
    6
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    I appreciate it, but I could use a bit of a challenge... I am an ex-programmer of PHP, C# .NET, and VB .NET, I am also an ex-telecommunications engineer, an ex-network engineer and an ex-automotive technician ... Surely it can't be that difficult once I get started... Besides, I have nothing else to do

    This particular temperature controller will be for my hydroponic tomato garden, in particular for the water/nutrient temperature, and to turn on a heating mat if the water / nutrients are too cold...

    Thank you for bringing that up to my attention, I will certainly reread it, a bit slower this time.
     
  5. STL

    Thread Starter New Member

    Nov 12, 2012
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    Thank you for the information, it's much appreciated, but I'm doing this for the experience.
     
  6. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Look at the DS1820. It is easy to use. Of course you will need a mcu like the pic.

    It even has alarms which seem pretty cool but I have yet to use.
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,436
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    Ok, so you have ex-pired.:D
    This project is doable but I suggest you take one step at a time.
    If Arduino is the route you want to go, get the Arduino and get programming.
    Which one? I don't know. I have not used one before. I suppose the Arduino Uno.
    Get an LCD display and make a 24-hr clock. You may use this later.
    Next make a thermometer.
    These two will get you started with learning the platform.
     
  8. STL

    Thread Starter New Member

    Nov 12, 2012
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    Thanks, will do.
     
  9. STL

    Thread Starter New Member

    Nov 12, 2012
    6
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    Yeah, early retired :)

    Sounds like a great place to start, and so I will, thanks for the info.
     
  10. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I guess you mentioned it. :) or at least a version of it.
     
  11. n1ist

    Active Member

    Mar 8, 2009
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    16
    Look at https://www.sparkfun.com/products/10747 for an assembled relay unit. There are other relay boards and shields for the Arduino, but this one is in a separate case and keeps the high voltage safely separate from your control circuit.
    /mike
     
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