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Automate Aquarium Fan — Parallax Forums

Automate Aquarium Fan

fantabulumfantabulum Posts: 7
edited 2013-10-15 22:51 in Accessories
I'm trying to automate some equipment and one part I can't figure out is controlling the fans. I haven't found a thermometer that seems appropriate for this task. I already have a thermometer that has the sensor (that's submersed under water) and the cable that runs to the display. Could I tear that apart to interface with my microcontroller? Right now I only have the homework board, but I'm not stuck with that one.

I'm open to suggestion as to what sensor I should be using, but if there is a better alternative (to using the one I have) I'd still like to know how that could be possible. I thought about putting one of the standard sensors pressed up against the glass, but I'm unsure how accurate that would be.

Thanks in advance.

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-10-10 15:32
    Welcome to the forums! There are a lot of things that make a difference as to which temperature sensor you want to use. What is the range of temperature you wish to measure? Where does the temperature need to be sampled? Will it require a probe or could you use a temperature IC on your control board?
  • pmrobertpmrobert Posts: 672
    edited 2013-10-10 17:55
    photo (9).jpg
    It's possible to make a fairly robust sensor using an LM34 chip, epoxy, heat shrink, your choice of cable and a couple of small copper or stainless plumbing fittings.
    photo (9).jpg
    1024 x 768 - 90K
  • fantabulumfantabulum Posts: 7
    edited 2013-10-10 19:41
    The temperature needs to be ≈ 78 - 82°F. The current sensor I have is a digital thermometer when the probe is submersed and the display is not. I have two questions:

    1) Can a regular digital thermometer be modified to "talk" to a prallax board?
    2) What is the appropriate sensor to measure water temperature?

    Also, it's salt-water, so I don't know that stainless-anything will work well, but I'll look into the LM34 - It may be the answer.
  • FranklinFranklin Posts: 4,747
    edited 2013-10-10 21:46
    Also, it's salt-water, so I don't know that stainless-anything will work well, but I'll look into the LM34 - It may be the answer.
    Good quality stainless should be OK. The lm34 can be "potted" in silicone and it should be protected but if you use the silicone caulk or the stuff that smells like vinegar let it fully cure before using it around fish. Also Adafruit has some food grade heatshrink you may be able to use.
  • pmrobertpmrobert Posts: 672
    edited 2013-10-11 05:46
    The home brewing folks use an assortment of stainless and Ti drywells for temp sensing. Yes, stainless in the marine aquaria environment is hit and miss - there are numerous stainless alloys and only a few of them will not either corrode or release nickel or copper ions into the water. A very small amount of copper in your tank will rapidly kill all your inverts so be careful. Ti is very expensive but is safe. You're needing to measure water temp correct? I would pot a sensor in a small capped PVC or similar plastic tube - see http://forums.netduino.com/index.php?/topic/3495-waterproof-temperature-sensor/ for an example. That sensor is easier to use than an LM34 as you don't need an ADC chip.
  • GenetixGenetix Posts: 1,747
    edited 2013-10-11 13:26
    Applied Sensors used an AD592 Temperature Probe that could be inserted in liquid. Instructions for building the probe are in the back of the text.
    Industrial Control and Process Control both used an LM34 to measure temperature and a small 12V brushless fan was control using a MOSFET.
    The texts are free to download and are compatible with your homework board.
    Parallax still sells the Process Control Kit for $40 if you find it useful.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-10-11 14:10
    fantabulum wrote: »
    1) Can a regular digital thermometer be modified to "talk" to a prallax board?

    Not easily unless it has some sort of data port. Without a data port, you'd need to go poking around with a logic analyzer to see if you can find a data line to tap into. So basicly, if you have to ask, then no, a regular digital thermometer can't be modified to talk to a microcontroller. (Almost any device digital or not can be made to talk to a microcontroller, but it's likely to take a lot of work and there are likely easier solutions.)
  • fantabulumfantabulum Posts: 7
    edited 2013-10-11 14:45
    Thanks for the help everyone! I think I got what I need to move forward. How do I remove the [unsolved] tag from this thread?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-10-11 15:02
    fantabulum wrote: »
    Thanks for the help everyone! I think I got what I need to move forward. How do I remove the [unsolved] tag from this thread?

    Edit the original post of the thread and select "Go Advanced". There is a drop down menu to use there.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-10-14 09:25
    I have seen the LM34 potted in many ways so it could be used in various applications. All you need for it to "talk" to a BASIC Stamp Module is an ADC such as the ADC0831, which provides 8-bits or 19.6mV per step. Or if you need better resolution you can use a 10-bit or 12-bit ADC.
  • kwinnkwinn Posts: 8,697
    edited 2013-10-15 22:51
    An LM35 (Celsius version of LM34) in a straw filled with epoxy has proven very reliable in a greenhouse for both air and water temperature.
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