Intelligent Thermostat: Creating Comfortable Environments by Considering Humidity, Study Guides, Projects, Research of Electrical and Electronics Engineering

Download Intelligent Thermostat: Creating Comfortable Environments by Considering Humidity and more Study Guides, Projects, Research Electrical and Electronics Engineering in PDF only on Docsity! The Intelligent Thermostat: A Novel Approach to Comfort Control ECE 445 Final Paper Student Design team: Matthew Gore Stuart Chen TA: Mo Zhou December 7, 2004 Table of Contents Introduction . . . . . . 3 Theory and Design. . . . . 4 Block Diagram and Description . . . 8 Circuit Schematic . . . . . 10 Microcontroller Flow Chart . . . 11 Design Alternatives . . . . 12 Testing / Verification. . . . . 14 Cost Analysis . . . . . 16 Conclusion . . . . . . 16 2 Instead of using the traditional heat-index equation, we found data for an indoor comfort-index (see figure 3-1).2 Unfortunately, although the data was attributed to the NOAA, they were unable to provide us with information regarding its source. As the data appears planar over the area we are interested in, we used a linear least-squared, best-fit method using Microsoft Excel (see figure 4-1). The mean difference between the given and predicted apparent temperatures (over the range of the supplied data) is .608°F and the max difference is 1.98°F. Given the fact that the original data was already rounded to the nearest integer, this additional error is negligible. The extrapolated equation is: CI = 1.058957219T + 0.0925H - 10.43983957 Because of memory constraints in the PIC, for processing purposes this equation was reduced to CI = 1.059T + 0.093H – 10.440 2 “Apparent Temperature for Values of Room Temperature and Relative Humidity” http://www.infoplease.com/ipa/A0001434.html 5 FIGURE 6-1 Indoor Apparent Temperature as a Function of Temperature and Relative Humidity Relative Humidity (% saturation) Room temperature (°F) 75 68 69 71 72 74 75 76 76 77 78 79 74 66 68 69 71 72 73 74 75 76 77 78 73 65 67 68 70 71 72 73 74 75 76 77 72 64 65 67 68 70 71 72 73 74 75 76 71 63 64 66 67 68 70 71 72 73 74 75 70 63 64 65 66 67 68 69 70 71 72 73 69 62 63 64 65 66 67 68 69 70 71 72 68 61 62 63 64 65 66 67 68 69 70 71 67 60 61 62 63 64 65 66 67 68 68 69 66 59 60 61 62 63 64 65 66 67 67 68 65 59 60 61 61 62 63 64 65 65 66 67 64 58 59 60 60 61 62 63 64 64 65 66 63 57 58 59 59 60 61 62 62 63 64 64 62 56 57 58 58 59 60 61 61 62 63 63 61 56 57 57 58 59 59 60 60 61 61 62 80 90 10040 50 60 700 10 20 30 FIGURE 6-2 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 0% 20% 40% 60% 80% 100% 0 10 20 30 40 50 60 70 80 Apparent Temperature (°F) Room Temperature (°F) Relative Humidity (% of saturation) Indoor Apparent Temperature as a Function of Temperature and Relative Humidity 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10 6 FIGURE 7-1 Predicted Indoor Apparent Temperature as a Function of Temperature and Relative Humidity Relative Humidity (% saturation) Room temperature (°F) 75 68.98195 69.90695 70.83195 71.75695 72.68195 73.60695 74.53195 75.45695 76.38195 77.30695 78.23195 74 67.92299 68.84799 69.77299 70.69799 71.62299 72.54799 73.47299 74.39799 75.32299 76.24799 77.17299 73 66.86404 67.78904 68.71404 69.63904 70.56404 71.48904 72.41404 73.33904 74.26404 75.18904 76.11404 72 65.80508 66.73008 67.65508 68.58008 69.50508 70.43008 71.35508 72.28008 73.20508 74.13008 75.05508 71 64.74612 65.67112 66.59612 67.52112 68.44612 69.37112 70.29612 71.22112 72.14612 73.07112 73.99612 70 63.68717 64.61217 65.53717 66.46217 67.38717 68.31217 69.23717 70.16217 71.08717 72.01217 72.93717 69 62.62821 63.55321 64.47821 65.40321 66.32821 67.25321 68.17821 69.10321 70.02821 70.95321 71.87821 68 61.56925 62.49425 63.41925 64.34425 65.26925 66.19425 67.11925 68.04425 68.96925 69.89425 70.81925 67 60.51029 61.43529 62.36029 63.28529 64.21029 65.13529 66.06029 66.98529 67.91029 68.83529 69.76029 66 59.45134 60.37634 61.30134 62.22634 63.15134 64.07634 65.00134 65.92634 66.85134 67.77634 68.70134 65 58.39238 59.31738 60.24238 61.16738 62.09238 63.01738 63.94238 64.86738 65.79238 66.71738 67.64238 64 57.33342 58.25842 59.18342 60.10842 61.03342 61.95842 62.88342 63.80842 64.73342 65.65842 66.58342 63 56.27447 57.19947 58.12447 59.04947 59.97447 60.89947 61.82447 62.74947 63.67447 64.59947 65.52447 62 55.21551 56.14051 57.06551 57.99051 58.91551 59.84051 60.76551 61.69051 62.61551 63.54051 64.46551 61 54.15655 55.08155 56.00655 56.93155 57.85655 58.78155 59.70655 60.63155 61.55655 62.48155 63.40655 40 50 60 700 10 20 30 80 90 100 FIGURE 7-2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 S1 S3 S5 S7 S9 S11 0 10 20 30 40 50 60 70 80 Apparent Temperature (F) Actual Temperature (F) Relative Humidity (% saturation) Predicted Indoor Apparent Temperature as a Function of Temperature and Relative Humidity 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10 7 Hantronix HDM16416L LCD Microchip PIC16F877 4.7K 4.7K +5 V +5 V 21 22 +5 V UP BUTTON DOWN BUTTON HEAT/COOL SWITCH 17 31-37 Temp Sensor +5 V Hum. Sensor +5 V National Semiconductor LM34 Honeywell HIH-3610 +5 V Figure 10-1 Circuit Diagram 10 Start Set defaults: Set temp to 70F Set activity to OFF Get sensor data What is operation mode? Calculate current index Compare current(temp or index) with setting Intelligent Standard Current equal to setting? Current high or low? User set to cool? Yes No Low Set activity to OFF Set activity to COOLING Set activity to HEATING User input? No yes No Increase or Decrease? No Yes Increase setting by 1F Decrease setting by 1F Figure 11-1 Microcontroller Flowchart User set to heat? High yes 11 Design Alternatives: The final implementation of our project is different than its conception. Heat/cool switch: Originally, the design did not include a heat/cool switch for the user to select a single mode of operation. In the spirit of minimizing user interaction with the device, we included a method for the device to decide. Instead of turning on heating or air conditioning the moment the ambient temperature strayed from the set point, we included a buffer of 2 degrees before activity began. In this way, the controller would know in which direction the environment was tending, and activate the appropriate system. There are two problems with this approach. First of all, in unseasonable weather, the user may not actually mind. For example, the user may have the temperature set lower in the winter or higher in the summer in order to conserve energy. In this case, the user has set the boundary for temperature in a particular direction, but the thermostat would have prevented it from straying in the other. Second, such a switch would require the pilot light to be lit at all times (or electronic ignition), which is not standard practice. The original processor flow chart is as follows: Start Set defaults: Set temp to 70F Set activity to OFF Get sensor data What is operation mode? Calculate current index Compare current(temp or index) with setting Intelligent Standard Current equal to setting? Current within 2 degrees? Current high or low? Yes No No Set activity to OFF Set activity to COOLING Set activity to HEATING High Low User input? Yes Increase or Decrease? No Yes Increase setting by 1F Decrease setting by 1F Figure 12-1 Original Microcontroller Flowchart 12 Behavioral testing: After we completed assembly of our device, we needed assurance that the thermostat would behave as designed under a variety of different conditions. We approached this stage of testing as if we were average users of a thermostat and ran the device under all combinations of mode (normal/smart), setting (heat/cool), and set points between the temperature and comfort index, greater than (less than) the temperature, and less than (greater than) the comfort index. Figure 15-1 – Behavioral Testing Mode Setting Temp Hum Index Set Pt. Action Evaluation Normal Heat 80.6° 27% 77.4° 76° None Pass Normal Heat 80.6° 26.30% 77.3° 79° None Pass Normal Heat 80.6° 26.80% 77.3° 82° Heat Pass Normal Cool 80.6° 26% 77.3° 76° Cool Pass Normal Cool 80.6° 25.50% 77.2° 79° Cool Pass Normal Cool 80.7° 26% 77.4° 82° None Pass Smart Heat 80.7° 25.60% 77.3° 76° None Pass Smart Heat 80.6° 27.50% 77.4° 79° Heat Pass Smart Heat 80.6° 25.40% 77.2° 82° Heat Pass Smart Cool 80.7° 25.50% 77.3° 76° Cool Pass Smart Cool 80.7° 25.60% 77.4° 79° None Pass Results: The component testing on the humidity and temperature sensors proved fairly successful in indicating the actual conditions of the environment. Although there was slight error overall in the readings, +/- 0.65° in temperature and 0.5% in relative humidity, these errors were within the inherent error of the Radioshack thermometer and hydrometer. Furthermore, the temperature error varied positively and negatively between different trials, so a linear change of our algorithm would not solve the problem. We concluded that the HIH-3610 and LM34 were fairly precise reflections of the relative humidity and temperature with sufficient accuracy for our purposes. The behavioral testing of the intelligent thermostat demonstrated that our prototype worked flawlessly. It passed each of our tests at a certain setting, mode, and set point. The output of the thermostat was clearly indicated with the LEDs and the arrow keys on the display of the LCD. Testing was completed in normal-cool, normal-heat, smart-cool, and smart-heat modes. In smart mode, it was verified that the thermostat used the comfort index as a target temperature instead of the normal temperature. The testing results of the intelligent thermostat behavior showed with confidence that the device works to our expectations. 15 Cost Analysis: (LABOR) Matthew ($75.00/hour) x 2.5 x 50 hours to complete = $9,375.00 Stuart ($75.00/hour) x 2.5 x 50 hours to complete = $9,375.00 Total = $18,750.00 (PARTS) PIC Microcontroller = $10 LCD Display = $20 Humidity Sensor = $14.00 Temperature Sensor = $22.00 Total = $66.00 GRAND TOTAL = $18,750.00 + $66.00 = $18,816.00 Conclusion: In conclusion, the device was successfully implemented. The idea and theory behind it proved useful, and the design practical. Testing showed that the device could be successfully calibrated and that all behavioral processes worked correctly. We believe that our device is ready for commercial development. Aside from miniaturization and improved “packaging” (and the addition of a voltage regulator to allow it to run off of home power), it is ready for the next step. While possible improvements include an energy saving mode or a season-sensing ability that negates the necessity for a heat/cool switch, we believe that in its current form the device has the maximum features with maximum usability. The device requires the user to learn nothing new and allows them to treat it exactly the same as a normal thermostat, with the exception that with this device they will find themselves comfortable without the need to fiddle with the thermostat. In effect, our device will prove its success by being ignored. 16