Wireless Controlled Residential Air Vent: A Smartphone Interface for Air Direction

Transcription

1 UNIVERSITY OF NEVADA LAS VEGAS DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING EE & CPE 497 Senior Design Fall 2014 Wireless Controlled Residential Air Vent: A Smartphone Interface for Air Direction Final Project Report Group Members: CPE Name (Print) Name (Print) CPE/EE/ME EE CPE/EE/ME

2 Introduction Air conditioning (A/C) vents are stationary with permanently fixed fins. This means that it can only direct airflow to the predetermined design of the vent. In some applications, the airflow is scattered to areas that don t need to be cooled or heated. For example, couches or other pieces of furniture where people tend to spend most of their time in a room can sometimes be placed in an area where the vents do not direct airflow to. Another example can be found in bedrooms where the bed is placed in a position where the airflow is directed straight to a resting person s face which in some cases can cause sinus problems. A need to manually control the A/C vents to direct airflow is the solution to these issues. Our project will have a full two dimensional control of the airflow coming out of a vent. It will be an easy bolt-on replacement for the standard vents already installed in residential homes and will be controlled via an application on a smart mobile device. Once the app is installed, the user will be presented with a layout that will represent the room and then the user will place the location of the vent. Once that is done, they will be able to select the area of the room they want to direct the air towards or they can set the vent to move in an oscillation mode. Depending on what they want, the vent can just move side-to-side, up and down or both at the same time. Because we have such control over the vent, we can also completely close the vent to a room with a simple button press in the app in the event that room is no longer needed to be heated/cooled System Specification The proposed air vent will take on the dimensions of the already available vents that can be found in residential homes. Figure 1 shows an image of traditional air vents that have fixed fins and do not possess the capability to be controlled without the assistance of manual labor if it is contains an opening and closing arm. Figure 1: Fixed fin air vents

3 Our air vent will possess two sets of fins with both layers arranged perpendicular to each other to achieve the two degrees of motion desired to be able to direct air to any location within the living area of the room. The top layer facing the room will have the fins arranged perpendicular to the floor. The bottom layer located inside the housing will have the fins parallel to the top layer and therefore resulting in the fins being parallel to the floor of the room. Figure 2 illustrates the two degrees of motion desired for this controllable vent. Figure 2: The two degrees of motion for the vent This architecture for the vent will allow it to be able to cover all the areas within the volume of the living space. Figure 3 illustrates the potential coverage given that both sets of pins can pivot 180 degrees with respect to the wall.

4 Figure 3: Coverage of one vent in a cube shaped room System Architecture A. Architecture of the Vent The system will comprise of two servo motors that will move the fins on the vent. One will be in charge of moving the x-axis and the other the y-axis. These servo motors will be receiving commands from a microcontroller and the micro controller will be receiving commands from RF transceivers. These RF transceivers will be receiving data from a smart device such as smartphone or tablet. Figure 4 shows the overview of the architecture of the design. The green box in Figure 4 is intended to show the items installed on the PCB and will be enclosed in a black box. This black box will be mounted on the back side of the vent where it will be hidden from sight inside the duct work.

5 Wi- Fi/ZigBee Transceiver µ Controller Power Supply Wind Flow Sensor PCB located on vent iphone Interface Mechanical Connection Power Wire Control Wire Figure 4: System Architecture The components chosen to be integrated into our design will be discussed below: I. Wi-Fi Module The module of choice is Digi s XBee Wi-Fi module. The part number is the XB2B-WFWT-001. The specifications of this module can be observed in the table below and has the PRO design. Serial Data Interface UART up to 1Mbps, SPI up to 6 Mbps Frequency Band ISM 2.4 GHz ADC Inputs 4(12-bit) Digital I/O 10 Operating Temperature -30 C to +85 C (-22 F to 185 F) Network Security WPA-PSK,WPA2-PSK and WEP Channels 13 WLAN Standard b/g/n WLAN Data Rates 1Mbps to 72 Mbps Transmit Power Up to +16dBm Receiving Sensitivity -93 to -71 dbm Supply Voltage 3.14 to 3.46 VDC Transmit Current Up to 309mA Receiver Current 100mA Dimensions(L X W) 27.61mm X 24.38mm

6 II. Microcontroller The microcontroller used for this application is Atmel s Atmega328P-PU. The specifications can be observed in the table below. Flash 32 KB EEPROM 1 KB RAM 2 KB Pin Count 32 Max. Operating 20MHz Frequency CPU 8-bit AVR I/O Pins 23 Operating Voltage 1.8V 5.5V Operating Temperature -40 C to +85 C (-40 F to 185 F) ADC 8 (10-bit) Power 1MHz, 1.8V, Active Mode: 0.2mA, Power-save mode: 0.75µA Data Retention 20 years at 85 C/ 100 years at 25 C III. Servo Motors The servo motors used was the Power HD-1501MG sold by Pololu. This is an analog servomotor that is controlled with pulse width modulation. The specifications can be observed in the table below. Limit angle 180 plus or minus 10 Weight 63 plus or minus 1g Operating Voltage 4.8V - 6.0V Operating Temperature -10 C 50 C (14 F F) Dimensions 40.7x20.5x39.5mm Stall Torque 17kg/cm IV. Wind Sensor The exact specifications for the wind sensor have not been sourced yet but it will most likely be a thermal anemometer. This is a device that uses something called a "hot-wire" technique. This technique involves heating an element to a constant temperature and then measuring the electrical power that is required to maintain the heated element at temperature as the wind changes.

7 This measured electrical input is then directly proportional to the square of the wind speed. This value will be sent to the microcontroller to let it know when the air has stopped flowing and to stop the vent from moving. This is to keep the vent from unnecessarily oscillating. V. Transformer This vent is meant to be installed in to an existing HVAC system but there is no power at the vent location in these existing systems. To remedy this, a transformer will be installed at the main HVAC unit that will take household 120V AC and convert it to 5V DC. Wires will then be snaked down the air ducts to each vent location. This will power each individual vent and at the same time will cut down on the costs associated with running power to each vent and also the cost of transformers at each location. B. Smart Phone Application/Microcontroller Software The RF transceiver will be receiving commands from a smartphone application. The application will be written for Apple handheld devices. The RF transceiver will communicate to the Atmega328P through the USART protocol. The Atmega328P will be flashed with a program written in C. The flow diagrams for the different softwares are presented below. I. iphone Application The flow diagram shows the initial setup prompts all the way down to the way how a customer will operate the air vent. The configurable options all though not linked in the flow chart, will be accessible at all at times. The user will be able to change the name of the vent to a more recognizable name for the configured air vent. This name will not be sent to the XBee Wi-Fi module since it will already be preconfigured with its own wireless address

8 Open Application Welcoming Screen displayed. Discover Devices Connect to Device Layout of Room Displayed User prompted to place estimate location of the vent in the room (parameter transmitted to module) User prompted to estimate how high the vent is from floor level (parameter transmitted to module) Another vent to program? User prompted to select area desired or place in oscillation mode (parameter transmitted to module) Change mode? Air vent continues mode until wind sensor interrupts

9 II. Atmega328P Software The microcontroller will be written in C and will be in charge of moving two servo motors. The flowchart below illustrates how it will be handling the parameters being sent from the iphone application. Figure 5 will serve as an assist to follow the flow chart. Figure 5 shows the PWM values at each degree of motion of the servo motor. For example, an OCR value of 2100 indicates the servo will point the fins at 180, OCR = 1200 points to 90, and OCR = 0 points to 0. The regions labeled with letters will summarize the desired location for the user. The prototype will assume vent is place in the center of the wall selected. OCR=2100 OCR=1700 A B OCR=1200 C D OCR=400 Figure 5: Air vent and the parameters it uses to direct air flow to the desired regions. This will serve for both servo motors, the one sweeping up and down, and the other that sweeps side to side.

10 Parameters Received Vent on Right wall? Region A? OCR sweep from 1700 to 2100 Vent on Left wall? Vent on Front wall? Vent on Back wall? Vent on Ceiling? Adjust parameter for height and initiate movement of horizontal fins Receive User parameter for desired airflow Oscillation Mode? OCR sweep from 2100 to 0 on both servo motors Region B? Region C? Region D? Initiate movement of vertical fins OCR sweep from 1700 to 1200 OCR sweep from 1700 to 400 OCR sweep from 400 to 0 Region A? Region B? Region C? Region D? OCR sweep from 1700 to 2100 OCR sweep from 1700 to 1200 OCR sweep from 1700 to 400 OCR sweep from 400 to 0 The above flow chart shows the flow of the code for a user selecting a single point in a region specified in Figure 5. The program will have the capability to select points that cross multiple regions but was not displayed in the flow chart due to limited space.

11 Subsystem/Component Alternative Generation and Trade-offs A. Wireless module For the wireless module we looked at several different options. For the design to work there needed to be a way for the Apple device to communicate with the microcontroller. Several options for this communication protocol included Bluetooth, ZigBee, direct RF, and Wi-Fi. I. Bluetooth was a promising option because so many people are familiar with it. The problem with Bluetooth is Apple devices can only connect to 2 devices at any one time. While this was fine for our prototype, this would not scale up if this design was ever expanded to more than 2 vents. II. III. IV. ZigBee is a nice robust protocol because it is self healing and creates a strong mesh network but the Apple devices cannot communicate directly without a gateway and that seemed like an unnecessary addition. The same was true for the standalone RF network. This left us with the Wi-Fi module as being the best choice. It consumes more power than all the others but we decided that ease of use for the end user was more important. The Wi-Fi module would allow an end user to connect the vent to the same wireless network their Apple device was already connected to and easily communicate with it. B. Servo Motor We had several consideration to make when choosing the servo motors to control the up/down and left/right of the vent. Torque, operating voltages, current draw, size, weight, and accuracy were all things considered when selecting the proper servo motors. Since this would be mounted to an air vent it would have to be small yet powerful and would hopefully work without having to add extra gears to work. Also, with the ability to select a certain position for the vent direction from the Apple device, it had to be accurate; being off by a few degrees at the vent could mean being off by a few feet once it reaches the other side of the room. I. PowerHD 3001HB - This servo was originally chosen because of its use previously in other projects. Familiarity with it made getting started much simpler for the first testing stages. It weighed in at only 43g and had relatively small dimensions(54.5mm x 20.5mm x 43.5mm) which made it easy to hide in the back of the vent. While it worked well, the stall torque (4.4kg cm) was too low for it to move the control arm for up/down control of the vent. To fix this, gears could

12 have been added to change the torque of the output, but it would come at the cost of speed and would also take up more room in the back of vent. II. PowerHD 1501MG - Built on the same form factor as the 3001HB but having a much higher stall torque (17kg cm), nearly the same speed, plus a nice price point made it an good choice to use for control. Since the code written to control the 3001HB worked and both were made by the same company with the same connections, it made it a simple swap to get 4 times the torque. C. Microcontroller Finding the proper microcontroller is an important task as well. It was important to find a balance between speed, features, and cost. In the search for microcontrollers we came up with 3 candidates from ATMEL because they have a robust user community and a great track record for supporting their products. I. SAM3X8E - This microcontroller has a powerful 32-bit ARM processor that would allow us to add any additional features in the future we could think of. It would also give us extremely quick processing speed to minimize delay from button press to system action. It turned out to be more processing power than we really needed so we moved to a lower tier ATMEL product. II. ATMEGA8 - This microcontroller has a 8-bit processor which we determined would be fine for the design but it only had 8KB flash which might not be enough if the design was ever expanded. Leaving room for expansion was one of the main goals in this project. III. ATMEGA328 - This microcontroller has the same 8-bit processor as the ATMEGA8 but comes with 32KB flash which opens the possibility of future expansion. Ultimately, this is the processor used for the design.

13 Design of the Circuit Figure 6 shows the wired connections involved between the servo motors, the microcontroller, the wind sensor, and the RF transceiver. A functional prototype was built based on this circuit. The prototype that was built ensured that wireless communication was able to be received by the XBee module that will send the commands to the microcontroller controlling the servo motor. Figure 6: XBee, Atmega328P, wind sensor, and Servo Motors wired connections

14 I. Functional Prototype Our functional prototype consisted of an XBee module simulating the data sent to the receiving XBee module. The mode was changed by changing the input on a pin on the Atmega328P from a high to a low and vice versa. The pin chosen was PB0 and when the pin was set to low, it would transmit an ASCII 0 to the receiving XBee module. The XBee module then passed it on to the Atmega328P in charge of controlling the servo motor. This would trigger an if statement in the code to have the servo sweep region A as referred to in Figure 5. Then when the pin would be set to high on the transmitting Atmega328P, the code would send an ASCII 1 to the XBee module which is then wirelessly transmitted to the receiving XBee module who would then have the Atmega328P change the servo s sweeping region from A to C continuously. Pictures of the functional prototype can be found below in Figure 7.

15 Figure 7: From top to bottom: 1. Side view of receiving circuit that controls the servo motor. 2. Top view of receiving circuit that controls the servo motor. 3. Side view of the circuit that transmits the user data. 4. Top view of the circuit that transmits the user data. This circuit performed ideally and it facilitates what kind of data will be transmitted to the microcontroller. Almost negligible delay occurred when transitioning from mode of operation. It was almost instant and the continuous sweep occurred without any errors. If no mode is selected, then the servo will not move. When the air sensor is obtained, it will connect to the

16 ATmega328P to cause an interrupt on PB7. This ensures the servo motors will stop spinning if the AC has stopped outputting air. Test Plan A. Present Design As stated earlier, the present design consists of two ATMEGA 328 microcontrollers connected to two XBee wireless modules. One microcontroller sends a command to the first XBee which then sends wirelessly to the second XBee which in turn relays that command to the second microcontroller. That microcontroller then sends a signal to the servo to tell it what position to rotate to. This design was built to show a proof of concept that we could these parts to accomplish wireless control of the servo motors. The first microcontroller and XBee module act as a simulation for the future Apple device that will ultimately be controlling everything. Once we have shown that these parts will work, we can then move on to the final project design that includes both servos and the Apple device. This is the test plan for the current design. I. Program microcontroller to oscillate between sending two different pulse widths to move servo between 90 and 180 degrees to ensure proper control of servo. II. III. IV. Program microcontroller to change between 90 degree pulse and 180 degree pulse by changing an input pin PB0 (14) from 5V to 0V. Setup and connect both XBee modules to each other by first connecting them to PC through COM ports. Test connection by sending serial string from one to the other and watching transaction on PC. V. Program "sending" microcontroller to send ASCII "1" or "0" depending on input pin voltage. Connect the TX pin (3) of the microcontroller to the RX pin (3) on the "sending" XBee. VI. VII. Connect to the "receiving" XBee with the PC and see if by changing the input pin on the "sending" microcontroller it changes the serial string received by the "receiving" XBee. Connect TX pin (2) of the "receiving" XBee to the RX pin (2) of the "receiving"" microcontroller and monitor output of the PB1 pin (15) on the "receiving" microcontroller to make sure the pulse width changes while changing the input pin voltage of the "sending" microcontroller.

17 VIII. Connect the PB1 pin of the "receiving" microcontroller to the signal input of the servo motor and observe the changes to the position of the arm of the servo with changes to the input pin voltages of the "sending" microcontroller. B. Final Design w that the parts have shown they will work, we can make the final design. The final design will have an custom Apple device interface that will send commands wirelessly to an XBee wireless module that will then relay the command to a microcontroller to change the position of each of the servo motors. Depending where the user taps on the screen, the servos will move the vent louvers into the correct position. I. Build frame to connect both servo motors to air vent control arms and attach servo motors securely to air vent. II. III. IV. Connect servo control inputs to output pins of "receiving" microcontroller. Make sure servos move to correct positions according to input pin conditions on the "sending" microcontroller. Build Apple device interface with simple up/down/left/right buttons to test communication between Apple device and microcontroller. V. Design GUI for Apple device interface to give end user ability to select direction of flow from air vent and test for accuracy. VI. Test range of Apple device control of vent. User Manual The user manual for operating the iphone application carefully follows the flow chart presented under part B of the system architecture topic. However, a detailed explanation of how to setup from the moment the product comes out of the box will be presented. A. Unboxing The package should consist of one air vent and the appropriate hardware to properly mount in the place of the old air vent. The dimensions of the new air vent should match those of the old air vent. B. Installing The black box will have a terminal strip where the power and ground will be connected. Professional installing would be recommended to run power wires to this device C. Downloading the Application

18 The application will be available in the Apple Store. Once the vent has been setup, and the application has been downloaded. You are ready to proceed to the step of configuration. D. Configuration Step 1: Open the application and ensure the vent is powered on. Step 2: Press the discover devices icon and wait for the application to display the device that is installed. Once the device has been found, click the name of the RF transceiver. Step 3: w that you have established a connection to the RF transceiver in the air vent. You will be displayed a layout of a room. Here you will be presented with an icon that looks like an air vent and you will drag and drop it in place of where your air vent is installed. Step 4: w you will be prompted to roughly estimate how high the air vent is placed off the ground. This is to ensure that the horizontal fins compensate for where the room floor is located. Step 5: The air vent has been configured and you will be prompted to program another air vent if more than one will be installed. If another vent is available, go back to step 2 so that the smartphone may discover another device, otherwise, proceed to part E. E. User Control w whenever you start the application, you will be presented with your connected devices and you may change the name if so desired (i.e. Living room, kitchen, etc.). Click on the device you want to operate and you will be presented with a square room and the location of the vent. w you will be able to control the air vent by pressing the CONTROL icon. By doing so, you will be presented with the option to select from three modes. Once the mode desired is selected, you will be presented with the representation of the room again so that you may select your desired locations, below you will find how each feature will work. 1. Single point direction. Touch a location in the representation of the room and have the air vent direct air flow to the desired location. 2. Multi point direction Touch up to 4 locations in the representation of the room so that the air vent can sweep air flow through these locations. 3. Oscillation Here it will fix the x-axis of the vent to aim at the floor, and the y-axis of the vent will sweep from left to right and then from right to left.

19 F. Extra Icons You ll be able to access the settings at all times where modifications to the parameters can be performed. Budget For the current design, it requires double the parts since we are using a microcontroller and XBee module to simulate the Apple handheld device. In the final design, the cost will be lower due to using only 1 microcontroller and XBee per vent. Since the initial parts order we were able to find better pricing on most of the items and if we were to buy them in bulk, the cost savings would be even more dramatic. Due to being poor college students, we only bought parts in the quantities needed and therefore had to pay extra per piece. Also, in the following table it is assumed that the end user will already have the Apple handheld device so it was not included in the cost estimate. Manufacturer Part Number Description Digi International Atmel PowerHD XB2B- WFWT-001 ATMEGA328- PU 1501MG Prototype Quantity Prototype Cost (per unit) Final Quantity (per vent) Final Cost Estimate(per vent) XBee Wi-Fi module 2 $ $29.59 Atmel Processor 2 $ $1.86 Servo Motor 1 $ $16.95 Unknown Wind sensor 0 $ $0.00 Unknown Breadboard 2 $ $0.00 OshPark PCB 0 $ $10.00 Misc. components 1 $ $30.00 Air Vent 0 $ $10.00 Prototype cost total Final Cost Total $ $115.35

20 Timeline and Future Meetings Throughout this first part of senior design, we met with our senior design advisors once a week from the moment we picked them. We will continue this method right when the second semester of senior design begins. The goals for the upcoming semester can be outlined in the table below. Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 - Presentation day Have the basic functionalities of the application finished. Have the air vent built so that the servo motors can be tested with the load Have the wind sensor integrated and properly interrupting the microcontroller program. Have the power supply circuit built with the landing terminals. Have more functionality available for the application. Start building the frame for our black box Start building our display for our presentation. Have the vent ready to have the black box mounted to it. Have full functionality of the application finished. Have the black box mounted on the vent and begin designing the PCB so that it may fit in the black box. Have entire schematic PCB done and sent out to have the PCB made. Start designing appealing graphics for the application s interface. Have the servo motors properly placed on the vent. Have our presentation display finished. Have the PCB and begin testing it. Have our final product finished and application fully operational Designing the aesthetics of the application to make it appealing to the eyes. Final adjustments to ensure accuracy of