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Hot Water Heater Alarm

Hot Water Heater Alarm. By: Mike Malloy Aaron Medsker And Scott Pilarczyk. Introduction. In medium large households running out of water is a common occurrence Our product provides the household with a LCD display that gives the amount of time of hot water that is remaining

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Hot Water Heater Alarm

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  1. Hot Water Heater Alarm By: Mike Malloy Aaron Medsker And Scott Pilarczyk

  2. Introduction • In medium large households running out of water is a common occurrence • Our product provides the household with a LCD display that gives the amount of time of hot water that is remaining • This allows the household to appropriate shower length as well as warn someone before getting into a cold shower

  3. Installation Wire Sensors

  4. Objectives Features: • Determines the areas of the tank that contain “hot” water; water above a temperature threshold and puts it on a display. • Wirelessly transmits hot water data to a microcontroller in another room. • Calculates amount of hot water remaining based on past hot water depletion times • Transmits this information to a display

  5. Outline of Project • Warns user of low hot water in an affordable way • System Includes Water Heater Elements: • Sensors to track hot water level • PIC to process data and front half of XBEE User Interface Elements: • Back half of XBEE to communicate wirelessly with display • LCD display at remote location

  6. Block Diagram

  7. System Overview LCD Transmitter Microcontroller 2 Microcontroller 1 Sensors Receiver

  8. Sensors • Microchip TC622EPA+ND Temperature Sensors

  9. Sensors • String of 8 evenly spaced temperature sensors that behave like switches • Sensors have a trip point that is set by a resistor using the formula: Rtrip = 0.5997 xT2.1312 • By approximating when water would be too cold we settled on 92O F or a resistance of 118kΩ across the sensor

  10. Sensor Hysteresis

  11. Sensor Testing • Sensor Switching Test: • Looked for switching time and sensor output level • Temperature test: • Measured TSET and time to switch. • Voltage Test: • Measured the lowest usable voltage that sensors would remain functional. • Tests were performed on sensors before and after waterproofing.

  12. Sensor Switching Test • While viewing sensor output on oscilloscope it was seen that sensors switched over an average time of 35µs • Had no noise or disruptions in dry testing some units became noisy after repeated wet testing

  13. Sensor Temperature Test • Thermometers were placed under heat or in water along with sensors to get a temperature reading • Switched according to hysteresis • <<1˚ of tolerance • Uncoated sensors switched immediately while coated sensors switched within two seconds of reaching the relevant temperature

  14. Sensor Temperature Test

  15. Sensor Voltage Test • After plugging the sensors into a power supply we decreased the voltage they received by .1 V, starting at 5 V • Tests revealed that input voltage could fall to 4.1V before sensor performance was affected.

  16. Waterproofing • Two Options • Plastics Simple, very cheap, easily accessible Shrink wrap, plastic wrap, plastic bags • Thermal Interface Materials(TIM’s) More expensive, needed to get from vender higher chance of success

  17. Waterproof Testing • Plastics -To test them they were left in water overnight and by the morning when we checked for water large amounts had already seeped in • TIM’s -Needed object with high thermal conductivity as well as a low electrical conductivity -Challenge was that these two properties are directly related -The theoretical perfect material would have been diamond

  18. Waterproofing Decision • Discovered chemical companies like Dow Corning and 3M make adhesives that serve this function • Settled on 3M material TC-2707 and TC-2810 thermally conductive adhesive

  19. XBEE • Interfaces with PIC via UART, baud rate 1200 - 230400. • Used to wirelessly send data from the water heater to the user interface. • Requires an input voltage from 2.8-3.4 VDC (verified in testing)

  20. XBEE Range Testing • Used ‘loop test’ to verify each XBEE would properly transmit/receive before using in circuit • According to data sheet should be able to transmit 100 ft through obstruction • Needed to be able to work on the same floor as well as between floors

  21. XBEE Testing Same Floor 2nd Floor Everitt Labs Worked the Length of the Hall ~140 ft (150 tiles*11’’)

  22. Everitt 2nd Floor Everitt 1st Floor Everitt Basement 246 EL ~ 50 ft through 2 floors 50 EL XBEE Testing Multiple Floors

  23. Modular Software Design

  24. 1st PIC • PIC18F2455 • Collect Sensor Data • Calculate Time Remaining • Send LCD data via XBEE

  25. Software Flow Chart, 1st PIC

  26. 2nd PIC • PIC18F2455 • Receive time data from XBEE • Send message to LCD display

  27. LCD • HD44780 - Industry Standard • Needs Min. 7 PIC I/O Pins • Application Maestro for LCD Routines

  28. Cost Analysis Wireless communication accounts for over 50% of product cost. Reduction could lead to a reasonably priced product.

  29. Future Tests • Long term tests on TC-2810 to verify that it will not degrade in water • Safety tests on all materials involved • Testing XBEE ranges in a house rather than the lab • More rigorous software testing for bugs

  30. Future Work • Water Proofing • Sensor performance degrading over time if not kept waterproof • Power supply problems(Reality vs. Theoretical calculations) • Installation and Aesthetic design

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