Transcript Automated Pool Maintenance System

Automated Pool Maintenance
System
Jonathan Arbogast
Janine Garnham
Ajay Suthar
Project Description
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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
RS-232 Cable
Embedded Controller
RS-232 Cable
Wireless Modem
Wireless Modem
Communication Path from
Home PC to the Embedded
Controller
Home PC
Project Description
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Modeling a Pool
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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
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Two screens are
available for the
user
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One main screen for
monitoring and
entering new settings
One screen to
schedule different
temperature settings
pH Specifications
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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
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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
Project Components
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HC12
Controller
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Pump
Acid Adder
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Alkaline Adder
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Hot Plate
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Component Placement Around the Pool
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Fish Tank
2 Temperature
Sensors
1 pH Sensor
Hot Plate
Acid/Base/Water
Pumps
Windows PC
HC12 uController
Wireless Modems
Internal Operation
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Interface to Sensors/Pumps/Hot Plate
HC12 Processing
Serial Protocol
Wireless Conversion
User Inputs
Interfacing to the Sensors
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pH sensor has one DC output
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Temperature sensor has one DC output
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Linearly related to the pH level
1.75V at a pH of 7
0.25V/pH level change
Varies linearly with respect to temperature
These voltage levels will be connected to
three ADC ports on the HC12
Placement of Temperature Sensors
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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
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Using simple windshield
washer pumps
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12V
2
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1
Washer
Pump
5V
3
150
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2
Q1
2N2785
1
2
1
7437
4
From HC12
2
R1
U1A
0
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
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Hot Plate Interface
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Crydom AC Relay
Controlled by a 1.6mA 5V signal
Can drive 12A at 120V AC on the output side
HC12 Processing
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Must respond to several
interrupt sources
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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
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Uses set start and
stop bytes for all
messages
All messages include
a checksum
All messages are
either ACKed or
NACKed
Serial Port
Initialization
Look for Start
Character (X)
Look for Stop
Character (Y)
Check the
Checksum
Send ACK
(XOY)
Parse the
Command
Send NAK
(XNY)
Wireless Conversion
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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
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T - Get the current temperature 
P - Get the current pH level
S - Set the desired temperature
C - Set the desired pH level
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Windows software
converts user actions
into serial messages
Sent over wireless
modem to the HC12 for
processing
Software is built using
Java
Wireless Demo
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Small demo of the wireless communications
Modems are setup in a loopback
configuration
System Verification
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A “second opinion” must be used to
demonstrate that the specs have been met
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Temperature checked with a digital thermometer
pH checked with a separate digital pH meter
Future Enhancements
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Base/Acid/Water Level Sensors
Chlorine Sensors & Dispensers
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Not included due to expense
Adjusting for different pool sizes
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Would change the amount of acid/base to add
Would change the temperature response times
Questions??