Rabbit Helps to Keep Pools Crystal Clear
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The Rabbit was found to be the most economical solution, and with Dynamic C® and RabbitWeb™, it was also very easy to program.
When Yves Grignon bought a home with a pool, he understood the need for pool maintenance but soon realized how keeping a pool clean and clear was not an easy task or an exact science. Bothered by the drawbacks to pool maintenance, Grignon developed an automatic maintenance solution using Rabbit’s MiniCore RCM5700.
Traditionally, pool maintenance requires a degree in chemistry and endless supply of patience. All kidding aside, pool maintenance is a balancing act in which the main goal is to keep a sanitary environment. Maintaining acidity, clarity and overall cleanliness of the water requires constant testing and adjustment of chemical additives. Grignon quickly discovered that pool maintenance can be time consuming and expensive.
“Keeping the pH and chlorine levels right was not only time consuming but it required tests based on interpreting the color of the water after adding some chemicals to it or the color of test strips after dipping them in the pool water,” says Gringon.
Grignon wanted to find a complete solution that would save time and money while improving the accuracy of maintaining a pool. Grignon found that particular electrodes can be used to provide accurate data on pH and oxidation-reduction potential (ORP) of the water. The ORP measures the water’s bacterial killing potential and is a more useful measurement for knowing when to add chlorine. Grignon decided to develop an automated pool monitoring and maintenance system based on ORP measurements.
“The colormetric methods of measuring pH and chlorine level in pools are imprecise, error prone, and the manual method of adding chemicals to correct the pH and chlorine level is time consuming. A microcontroller based system was required to improve precision and eliminate the workload,” explains Grignon.
At the heart of this system is the MiniCore RCM5700. The RCM5700 acts as the main controller as well as a web server. Connected to the RCM5700 are analog sensors that measure the pool’s pH, ORP, temperature and pressure. The sensors are connected to an MSP430 16-bit analog front end, which then connects to the RCM5700 via an SPI connection. Also connected to the RCM5700 are relays that control the pool’s pump, fill valve for water level, and chemical injection pumps. During normal operation, the RCM5700 continuously monitors the pool’s condition. This information is converted into engineering units using calibration constants and is kept in flash memory. The ORP and pH data is used to calculate how much chlorine and acid to add to the pool using proportional-differential (PD) control algorithms. If the pool’s values shift, the RCM5700 will communicate with the acid and chlorine pumps to administer the right concentration.
The RCM5700’s web server capability allows the pool maintenance system to be accessed from any computer in the world with an Internet connection. Temperature, pressure, pH and ORP are displayed on the webpage along with the status of the filter, pump and chlorination. The web access also allows for manual operation of the pool pump and chlorination via web page buttons.
Its compact form factor, robust features for monitoring and control, and web connectivity made the RCM5700 ideal for this project.
“The Rabbit was found to be the most economical solution, and with Dynamic C® and RabbitWeb™, it was also very easy to program,” says Grignon.
Dynamic C and RabbitWeb were instrumental to the ease of use and quick development of this application. With the MiniCore RCM5700, Yves Gringnon has found a way to make pool maintenance nearly maintenance free.
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