Re: Re: Using OSPI as a Pool Chemistry Monitor

My goal for version 1 is to simply automate the monitoring of my pool’s chemistry over time (mine is a saltwater pool and spa).
Basically I want to be proactive and forewarned rather than my current reactive approach to pool chemistry
management (wait until my wife tells me there’s algae growing :-). If there was a constant data feed (say, to Xively),
then I could better predict when levels call for manual intervention (add salt, add stabilizer, add acid, etc.)
I’m not sure about the alerts or chart color variation available from Xively, but it would be cool to color the
charts green, yellow, orange, and red based on intervention required (green = all good; yellow = you have two weeks to do something;
orange = one week to do something; red = you are too late, don’t go swimming until you’re back to green!)

Here are some notes and links that I’ve collected so far:

• Other projects:

  • The Open Spa Monitor (SpaSitter) Arduino project
    http://openspamonitor.blogspot.com/
    (unpublished design, no pre-assembled hardware integration offered like OSPi)
  • Salt Water Aquarium (“Reef Keeping”) Forums
    http://www.reefcentral.com/forums/showthread.php?t=1968389
    http://www.ultimatereef.net/forums/showthread.php?t=545407&page=13
    (growing movement for RPi for aquarium water chemistry management)
  • Polysensor
    http://www.dil.iitb.ac.in/poly/project_details.htm
  • Jarduino
    https://code.google.com/p/jarduino-aquarium-controller/
  • Myron L hand-held water quality meter:
    http://www.isopurewater.com/Myron-L-6PIIFC-Ultrameter-II-Meter-Conductivity-TDS-Resistivity-pH-ORPFree-Chlorine-Temperature_p_5760.html

• Sensors:

  • ORP/pH sensors on Phidget:
    http://www.phidgets.com/products.php?category=36
  • ORP/pH sensors from Atlas Scientific:
    https://www.atlas-scientific.com/product_pages/sensors/orp-sensor.html
    https://www.atlas-scientific.com/product_pages/sensors/ph-sensor.html
  • Light Photo Cell and Temperature sensors (digital preferred, as we only have 4 A/D “ports”):
    http://chicagodist.com/products/waterproof-ds18b20-temperature-sensor-for-raspberry-pi-arduino
    http://www.adafruit.com/products/161#Description
    http://microcontrollershop.com/product_info.php?products_id=4408
  • DrDaq Data Logger board (interesting add-on board with lots of sensors and A/D capability:
    http://www.drdaq.com/

• ORP for Pool Water Quality information:

  • Using ORP and pH for pool chemistry monitoring background:
    http://www.rhtubs.com/ORP.htm
    http://www.eutechinst.com/techtips/tech-tips27.htm
    http://www.myronl.com/PDF/application_bulletins/orp_ab.pdf
    http://www.gfsignet.com/go/?action=GF_DocumentDownload&doc_uuid=4A79220919993E1D34532B2B8A683C6D

    The most ubiquitous and cost-effective sanitizing agent used in disinfection systems is chlorine.
    When chlorine is used as the sanitizer, free chlorine measurements are required to ensure residual
    levels high enough for ongoing bactericidal activity. The conversion of ORP measurements to free chlorine
    is accurate when chlorine is the only oxidizing/reducing agent in solution and pH is stable between 5 and 9.
    This pH range fits most applications because pH is usually maintained such that the most effective form of
    free chlorine, hypochlorous acid, exists in the greatest concentration with respect to other variables such
    as human tolerance.

    ORP (Oxidation Reduction Potential) or Redox is used in pool water treatment as an indication of sanitation
    in relation to free chlorine parameter. ORP technology has gained recognition worldwide and is found to be a
    reliable indicator of bacteriological water quality. Referencing a table that illustrates the kill time of
    E.Coli bacteria as a function of ORP value: with a value of 600 mV, the life of the bacteria is almost 2 minutes; at 650 mV it reduces to 30 seconds;
    above 700 mV the bacteria is killed within a few seconds. It is therefore necessary for the water to have an ORP value of at least 700 mV to ensure good water quality.

• WiFi USB dongles for Raspberry Pi (not exhaustive):

  • http://chicagodist.com/collections/adafruit-products/products/wifi-usb-for-raspberry-pi
  • http://chicagodist.com/collections/adafruit-products/products/long-range-wifi-usb-with-antenna-for-raspberry-pi

I think OSPi would give me a fast start–all I’d need are the following:

• 1 Raspberry Pi Rev B 512MB board (’cause its the latest!)
• 1 WiFi USB dongle
• 1 OpenSprinklerPi v1.2 board (need those 4 A/D channels)
• 1 ORP sensor probe
• 1 pH sensor probe
  just the analog probes, no interface cards required as they’ll connect directly to the OSPi A/D solder points
• 1 temperature sensor probe (likely analog to connect to an A/D port like the other probes)
• 1 ambient temperature sensor (preferably digital in the box (maybe) so I don’t have to use an A/D port)
• 1 “sunlight” phot cell sensor (optional later integration, preferably digital so I don’t have to use an A/D port)
• 1 probe container or something to harness the three probes together for constant immersion in the pool water
• 3 BNC connectors to mount on the box to interface to the analog sensors
• For power, I would connect to my existing 24VAC feed going into my pool light controller