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Automated Pool Maintenance System. Jonathan Arbogast Janine Garnham Ajay Suthar. Monitors and controls pH and temperature of a swimming pool Wireless control from a graphical interface on the customer’s PC inside the home
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Automated Pool Maintenance System Jonathan Arbogast Janine Garnham Ajay Suthar
Monitors and controls pH and temperature of a swimming pool Wireless control from a graphical interface on the customer’s PC inside the home Allows for multiple temperature settings to be entered for different time periods Project Description
Project Description • Modeling a Pool • Pool is replaced with a 20 gallon fish tank • Pool pump is replaced with a small circulation pump • Heating system is replaced with a hot plate
User Interface • Two screens are available for the user • One main screen for monitoring and entering new settings • One screen to schedule different temperature settings
pH Specifications • Recommended pH levels for a pool are 7.2 to 7.8 • The system will be able to control the pH level to within ±0.1 pH units • The pH sensor has a sensitivity of 0.02 pH units
Temperature Specifications • The accuracy of the monitored and controlled temperature will be within ±1C when heated • The resolution of the temperature sensor is 0.07 °C with a range between -15 °C and 100°C
Project Components • Fish Tank • 2 Temperature Sensors • 1 pH Sensor • Hot Plate • Acid/Base/Water Pumps • Windows PC • HC12 uController • Wireless Modems
Internal Operation • Interface to Sensors/Pumps/Hot Plate • HC12 Processing • Serial Protocol • Wireless Conversion • User Inputs
Interfacing to the Sensors • pH sensor has one DC output • Linearly related to the pH level • 1.75V at a pH of 7 • 0.25V/pH level change • Temperature sensor has one DC output • Varies linearly with respect to temperature • These voltage levels will be connected to three ADC ports on the HC12
Placement of Temperature Sensors • One sensor placed at the pump output • One sensor placed at the other side of the pool • Running average will be used
Interfacing to the Pumps • Using simple windshield washer pumps • Controlled by a 12V signal • Circuit based on a Darlington Pair will be used to convert the 5V output from the HC12 to a 12V signal with enough drive capability
Interfacing to the Hot Plate • Hot Plate Interface • Crydom AC Relay • Controlled by a 1.6mA 5V signal • Can drive 12A at 120V AC on the output side
HC12 Processing • Must respond to several interrupt sources • pH Sensor • Temperature Sensors • Must make decisions based on the user’s settings • Must control the hot plate and pumps to satisfy the user’s settings
Serial Protocol We will use a higher level protocol to check for errors and recover from them • Uses set start and stop bytes for all messages • All messages include a checksum • All messages are either ACKed or NACKed
Wireless Conversion • Conversion to wireless signals is handled by MaxStream modems • Buffering at both the input and output side • Translation between RS232 and 5V CMOS is handled by converter board.
User Inputs • Windows software converts user actions into serial messages • Sent over wireless modem to the HC12 for processing • Software is built using Java
Wireless Demo • Small demo of the wireless communications • Modems are setup in a loopback configuration
System Verification • A “second opinion” must be used to demonstrate that the specs have been met • Temperature checked with a digital thermometer • pH checked with a separate digital pH meter
Future Enhancements • Base/Acid/Water Level Sensors • Chlorine Sensors & Dispensers • Not included due to expense • Adjusting for different pool sizes • Would change the amount of acid/base to add • Would change the temperature response times