Overview Of pH and ORP Arduino Sensor

Make the SpaSitter 2.0, an open source hardware project based on the Arduino, to perform web based monitoring of the water chemistry for swimming pools, hot tubs, spas and other water bodies.  We have spent over a year testing the continued use of the pH and ORP (Oxidation Reduction Potential) probes in a hot tub environment.   They remain very accurate and react great to changes in water chemistry.  These high quality probes are expensive, but will out last any cheep commercial monitor, and they can be reconditions and calibrated!

Its easy to use!  Drop the sensors into the water and put the electronics in a water proof project box.  Run a Ethernet line out to the monitor and plug it into a power supply.

• Temperature monitoring -  A stainless steal encapsulated DS18B20 one wire temperature sensor for water proof temperature readings. 
• pH monitoring / ORP  monitoring -  Determine when your hot tub or swimming pool needs chemicals before it gets green or cloudy.  After heavy use the ORP level drops dramatically if there is not enough sanitation added to the water.  Optimum readings should be around 7.6 pH and 700 mV. 
• Email or text message alerts -  Cosm.com has great options and add on features that alert you when your chosen parameter falls outside a selected value. 
• Smart phone access - Add a Cosm widget to your smart phone and always have access your pool or spa conditions.
• High quality probes -  The kit comes with industrial grade pH and ORP probes.  Ideal for prolonged reading.  High polymer gel-filled design requires virtually no maintenance as there is no need to refill the reference chamber.

About

Anyone who has owned a hot tub knows that without keeping a close eye on the water with test strips and water test kits, a hot tub can quickly get green, cloudy, and unusable. A pool can often be just as hard to manage. Monitoring the temperature, pH, and ORP 24/7 and alerting you when chemicals need to be added is a valuable tool to stay on top of managing your water. This was my motivation behind the SpaSitter, an open source spa or pool monitor using a Nanode (an Arduino based network enabled node) and Cosm.com 's easy graphing API and triggers. Now you can always have easy access to your water conditions on your smart phone or the web. Set up email alerts to notify you when water conditions start to degrade.

The  SpaSitter is an open source, easy and simple way to get reliable and accurate readings on the current sanitation and chlorine levels of your hot tub or pool.  Monitor temperature, pH, ORP 24/7 and set up your own alerts with Cosm.com.

Here are some benefits to Open Source Hardware and a great resource for more info.

Open source is great way to build things, there are numerous support articles on the web for building a Nanodes and trouble shooting code.  There is a community of active makers in forums that are willing to help answer questions if you get stuck.  The hot tub monitor is open source so please feel free to copy and improve on the design.  We just ask that if you improve it, you share the new design.  If you make the design commercially, we ask that you pay a small royalty for supporting the projects continued development and community support.  We ask that you attribute the OpenSpaMonitor project.  The un-spoken rules of open-source hardware business is a great reference.

Building your own products allows you to fix it when broken, the product shelf life becomes much longer when you can replace one broken part instead of the whole commercialized product.  The product can also become re-purposed easily into other applications instead of throwing it away at the end of its use.

Being able to calibrate and recondition the monitor on your own means the hot tub monitor or SpaSitter will last much longer than other devices currently on the market.  Using industrial probes designed for continued use mean that there is virtually no maintenance, the gel filled reference solution never has to be refilled.

Customization is an amazing factor in open source hardware projects. There are many ways you can make the SpaSitter your own.   Change the source code to report to your own server.   Add a Twitter account to your hot tub or spa and have it tweet you.  Build an embedded event log that details your chemical applications and usage of your pool or spa. The list is endless.

We are based in Breckenridge Colorado,  USA.   Contact Us

SpaSitter Documention

SpaSitterTM 2.0 

How to build your own Spa or Pool Monitor. 

Pool Monitor, Hot Tub Monitor, Aquarium Monitor to Cosm.com

Nanode Classic with Opti Boot 

The Nanode, developed in the UK by Ken Boak in cooperation with the London Hackspace

Code adapted from OpenEnergyMonitor.org 

Authors: Trystan Lea, Glyn Hudson and Francois Hug

Part of the: openenergymonitor.org project

Licenced under GNU GPL V3

Step 1

Assemble your Nanode 5 with an Opti Boot Loader (pre-assembled boards are available when requested)

Link:  http://wiki.london.hackspace.org.uk/view/Project:Nanode/Building_a_Nanode

Or 

Nanode RF with no RF module 

Link:  http://ichilton.github.com/nanode/rf/build_guide.html

Step 2

Build a temperature shield with the water proof DS18B20. Use digital pin 8 on the Nanode as the one wire input pin.  The red wire is 5V power, black is ground, and yellow or white is digital input.

Breadboard schematic of DS18B20

Simple DS18B20 shield with water proof probe

Step 3

Solder the Phidget 1130 pH and or ORP boards to the Nanode board.  Red is 5V, black is ground, and white is the analog input.

Analog Pin 0 is the pH probe input, analog Pin 5 is the ORP probe. 

Both pH and ORP boards from Phidget are attached to the Nanode

Wiki:  http://www.phidgets.com/docs/1130_User_Guide

Connect the pH and/or ORP probe and select the correct setting on the indicator switch of the Phidget 1130 board.

All sensors attached to the board: Temp, pH, and ORP

Step 4

Now its time to put it all together.  Setup a Cosm.com account.  Here is a great tutorial at Adafruit Learning System.

Download the Arduino IDE software:  http://arduino.cc/en/Main/Software

Download the sketch for the Nanode at github: https://github.com/brianhuebner/OpenSpaMonitor2/tree/master/Nanode_SpaSitter_monitor_V_1_0
* Code adapted from the OpenEnergyMonitor.org  authors Trystan Lea and Glyn Hudson 

** Note, you need an FTDI cable for uploading the sketch to the Nanode

Add your Cosm.com feed ID and API key to the part of the sketch below:

Upload the sketch to the Nanode with a FTDI cable.  Plug in your Ethernet cable from your router to the Nanode and watch as it uploads your probe readings to your Cosm.com account.

Chemicals were added to the hot tub.  Our pH is low but the ORP is getting better. 

Step 5

Get some standard reference solution for you local hydroponics grow store.  Also fill a spray bottle with distilled water for cleaning the reference solution off of the glass probe junction.   Do not touch the glass probes with your fingers, as it leaves oil residue that will influence your reading.

Two calibration points will be fine pH 4 and pH 7.  Get some glass wear from the kitchen and add some reference solution.  Put the pH or ORP in the solution and wait for the value to adjust, one or two minutes.  You can use the serial monitor on the Nanode ( un-comment out the #debug  serial.print function) to read the output of your pH and ORP probe.   After one point calibration, spray the glass junction with distilled water for a couple minutes before putting it in the other standard solution.

The ORP reading for the standard reference solution is as follows:

pH Value	mV Value	pH Value	mV Value	pH Value	mV Value	pH Value	mV Value	pH Value	mV Value
0	990	3	800	6	640	9	460	12	280
1	920	4	740	7	580	10	400	13	220
2	860	5	680	8	520	11	340	14	160

The ORP probe in the pH 4 reference solutions should read around 740 mV and the pH 7 reference solution should read around 580 mV.


Now that your probes are calibrated and your SpaSitter is tested and working, its time to install it.  Run an Ethernet cable and power supply out to your  hot tub, pool or other water body and put it all in a water proof project box.   Have fun with your new SpaSitterTM.   Setup email or text message alerts to notify you when the conditions of your water need attention.  Add the Cosm.com widget to your smart phone for easy access to your SpaSitter.