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 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. A= x10 -4 B= x10 -4 C= x10 -7

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

System Schematic

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

Work Division 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 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 DescriptionUnit PriceQuantityTotal Price Evercool 12VDC CPU Fan $3.004$12.00 Radio Shack DC Switched AC Plug- In-Relay $3.002$6.00 Radio Shack 103-AT Thermistor $2.502$5.00 Generic Light Bulb (75W) $1.002$2.00 Generic Visual Thermometer $1.502$3.00 Zone Plexiglas material$5.002$10.00 Wiring (Cable, LED’s, copper wire, connectors, etc.) $ Motorola HC-12$ Free Total--$56.00 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

Questions, Suggestions?