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Linked Thermostat . Alan Diamond Ravi Patil. Objectives. Temperature sensing device Multizone capabilities (two) Heating and Cooling operation Personal computer software interface Internet accessible. Applicable Skills. Data Acquisition Feedback System Sensor Calibration
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Linked Thermostat Alan Diamond Ravi Patil
Objectives • Temperature sensing device • Multizone capabilities (two) • Heating and Cooling operation • Personal computer software interface • Internet accessible
Applicable Skills • Data Acquisition • Feedback System • Sensor Calibration • AC/DC Circuit Design • Internet Connectivity • JAVA, HC-12 Coding • Project Experience
Temperature Sensing • Radio Shack Model 103-AT (10k @ 25°C) • ± .3°C Precision • -50°C to 110°C Range • Application Range 20°C to 40°C (68°F to 104°F) • Within application range, linear voltage-temperature relationship
Temperature Sensing Using the Steinhart equation and the provided specifications, one can obtain the output voltage of a thermistor.
Heating Unit • Household light bulb with lamp fixture • Standard 75W light bulb • 12VDC activated 10A relay • Activated by HC-12 5VDC signal • Relay driven by common emitter ckt • Relay connected to AC signal from wall outlet
Cooling Unit • Utilizes 2 CPU fans per zone • 110mA, 33W 12VDC fan • One draws in airflow, the other pulls out airflow • Fans driven by common emitter ckt
Zone Construction • 10”x10”x10” cube • Plexiglass material • Sensors in front • Heating in back • Cooling in sides • Wires through back
Serial Interface • Standard RS232 serial port • Interfaced with JAVA • Sun Javax.comm package • Provides serial port class
Preliminary User Interface • PC software interface • Set and view zone temperatures • Accessible over the internet • using remote web server
System Power Consumption • 120VAC wall-powered system • Heating requires 75W • Cooling requires 1.3W • HC-12 requires minimal power
Project Testing • Sensor calibration – received thermistor voltage versus visual thermometer reading (± 2°F ) • Correct heating/cooling functionality according to current temperature • Web server integration • Separate component testing • Full system integration testing
Alan Diamond Web Interface Zone Construction Circuit Design Hardware Testing Sensor Calibration Ravi Patil JAVA Serial Interface HC12 Assembly Coding Zone Construction Hardware Testing Sensor Calibration Work Division • Both • Project Website • System Integration • System Testing • Project Report
Completed Work • JAVA Serial Interface • Most of HC-12 Coding • Sensor Calibration • Cooling Unit • Partial Heating Unit • Preliminary User Interface
Not Completed Work • Zone Construction • Finalized Circuitry • Finalized User Interface • Heating Unit Integration • Hardware Testing • Web Server Interface • Project Website
System Cost NOTE: Motorola HC-12 provided free-of-charge from the CE dept.
Safety Precautions • AC powered components • Appropriate cabling with insulated wiring • Heating unit can reach high-temp. • Heating unit can spike up to 7A • Zones made of fire-resistant material • Temperature constraints (104°F) lower possibility of fire