1. Automated Pool Maintenance System Jonathan Arbogast Janine Garnham Ajay Suthar

2. Project Description 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

3. 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

4. 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

5. 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

6. Temperature Specifications The accuracy of the monitored and controlled temperature will be within ±1  C when heated The resolution of the temperature sensor is 0.07 °C with a range between -15 °C and 100 °C

7. Project Components Fish Tank 2 Temperature Sensors 1 pH Sensor Hot Plate Acid/Base/Water Pumps Windows PC HC12 uController Wireless Modems

8. Internal Operation Interface to Sensors/Pumps/Hot Plate HC12 Processing Serial Protocol Wireless Conversion User Inputs

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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.

16. User Inputs Windows software converts user actions into serial messages Sent over wireless modem to the HC12 for processing Software is built using Java

17. Wireless Demo Small demo of the wireless communications Modems are setup in a loopback configuration

18. 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

19. 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

20. Questions??