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Question on long distance soil temp testing

Discussion in 'General Electronics Chat' started by fastline, Nov 17, 2016.

  1. fastline

    fastline Member

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    Curious as I have not checked geo data in your area but can you not just go deeper for a good geo loop? What is the ground water temp on average?
    Also, IIRC, the wind blows there? I guess if you have other heat sources, wind might be too costly but that can work well to simply dump all wind genny heat to a resistive heater for radiant heating.

    The reason I am doing radiant tubes in the whole shop is I then have a LOT of options. I like automation in which waste oil is easily automated. Wood can work too but not set and forget. In any case, I plan to use a water/water exchanger to eliminate any contamination concerns. The way things are getting done, I should have lots of ways to tune the system and if the geo system runs as designed, I may run it more.
    I also plan to cool the slab in summer too. I hate to use the term "radiant cooling" because we know that won't really work but I want to remove extra heat gained by the slab from surrounding hot soil. I have learned that the slab can get to 90*. Just getting that back closer to dew point should significantly reduce cooling loads.
     
  2. fastline

    fastline Member

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    Well, geo field lines would probably need to jog about 300ft. I would probably have 5-7 sensors out there. Indoors I will have another 10 sensors or so with short runs only.

    I realize I may not find a module that can digest all this in one unit but maybe? Eventually I have will have to walk into some type of PLC type device to module a few things based on these thermal inputs but for now, I just need to see the data. Is there maybe a down and dirty way to simply use some USB converter so I can review the data via a laptop? Maybe not ideal though.

    What I need to work towards is bring all this data into a PC for logging so I can log other variables such as indoor/outdoor temp, RH, etc.

    Also, in looking at that sensor, I am not sure +/- .5C accuracy is acceptable. 1 F can make a difference for me in terms of BTU calculations. I might like to see a resolution to .1-.2F
     
  3. spec

    spec Well-Known Member Most Helpful Member

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    Perhaps go for a Raspberry Pi as the data gathering/collating engine. A Pi has a lot more processing power than an Arduino. An Arduino may still be good for controlling each temperature sensor though.

    Am I correct in thinking that a wireless link to each temperature sensor is not possible because the temperature sensors will be buried underground?

    Just to support what TCM said: it is vital for this project's success to get the high-level system design sorted.:)

    spec
     
  4. dave

    Dave New Member

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  5. fastline

    fastline Member

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    well, again, my thought process was to simply install down tubes at each required probe site and then install a home run conduit out to that location as an "if needed" deal. If I can find a way to run wirelessly on the cheap and easy, great, but I might need to get power out there anway in which if I run the 1 wire systems, I could run a 3 wire cable for power out, and signal back in. There won't be any additional electric lines in that trench to cause issues but I did hear the part about stacking capacitance.
     
  6. spec

    spec Well-Known Member Most Helpful Member

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    .
    Thanks for information FL.

    By the way, you can run power and data down two wires; three wires are not necessarily required.

    There are two basic typologies for this kind of system:

    (1) Circle
    (2) Star

    Star would seem to be the optimum choice in this case.

    Would it be practical to physically have one interface unit (IFU) having one input connector for each temperature sensor?

    If so, what would the absolute maximum length of communications cable that would be required from any one individual temperature sensor and the IFU? UPDATE 2016_11_20 Whops. I see you have alresdy stated this = 300 feet.:arghh:

    spec

    PS: what State are you at? If you put it next to 'Location' on your user page it will show in the box at the left of your posts.
     
    Last edited: Nov 19, 2016
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You could either run it all direct from a PC, or use a micro-controller to read the sensors, and transfer the data to a PC - it really makes little difference.

    As you're only talking about less than 20 sensors it's fairly simple to do.

    My current PC based wireless monitoring I'm playing with would easily do 20 'as it is', as it currently uses 1 byte ASCII codes to identify each sensor (I'm using A, B, C and D for four).

    Or as already suggested, a PI would easily do it - or an Arduino, or PIC based board.
     
    • Informative Informative x 1
  8. Pommie

    Pommie Well-Known Member Most Helpful Member

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    If you go the one wire route then make sure to identify each chips ID number before installation.

    Mike.
     
  9. spec

    spec Well-Known Member Most Helpful Member

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    What software did you use, or was it GoodwinSoft?:)

    spec
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    A program I wrote using Lazarus - here's a screen sample from November, with three sensors.

    13Nov16.png
     
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