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1、Rain Detection for Power WindowsIn AutomobilesECE 445 Senior DesignGroup 4TA: Austin KirchhoffRobert HerzogBrian MittererChintan PatelI. Introduction1. Motivation: This project idea was selected because we all are interested in working with and learning about sensors, microcontrollers, and automobil
2、e electronics. We are excited about this project because we will be building and testing our own sensor system and implementing it into a vehicle. 2. Objectives: The main goal of the rain detection system is to grant the driver the convenience of having his or her car windows automatically close in
3、the event of rain. The rain detection system will sense when it begins to rain outside by detecting rain water from a moisture impedance sensor located on top of the vehicle. This sensor then sends a signal to a microcontroller located inside the car, which in turn sends a signal to drive the window
4、 motors to close the windows and sunroof if they are not completely closed. This system is to function both while the vehicle is running and when the vehicle is turned off. In addition, the system will have a switch which could turn the rain detection system on and off. Features- Rain detection whic
5、h closes all vehicle windows when the vehicle is on or off- ON/OFF switch located close to the driver so driver can override system at any time- Rain sensor made with impedance moisture technology which makes it cheaper, durable, and more reliable than other rain sensors on the market- System will b
6、e marketable and can be implemented into most vehicles with power windows Benefits- Protects the inside of a vehicle from water damage caused by rain- Provides safety to the driver and passengers since it eliminates the distraction of having to close the windows and sunroof manually by pressing swit
7、ches- Provides convenience to drivers by allowing them to keep windows open while they are away and not having to rush out to close them if it begins to rainII. Design1. Block Diagram:MicrocontrollerMotor / car controller for power windowsOverride Switch/ ControlSensorsVoltage RegulatorCar Battery2.
8、 Block Descriptions:Sensor OverviewWe will design and build three different rain sensors for our system. Which sensors we end up using in our final detection system will be a matter of how well they each perform. Through rigorous testing we will eventually decide which sensor or combination of senso
9、rs is best suited for our project. All three sensors will receive power from the car battery. A voltage regulator may be used to drop the 12 V from the car battery to a voltage level that is better suited for the particular sensor. Each sensor will complete a circuit in a unique way and allow curren
10、t to flow through it and to the microcontroller. Thus, we will include a high wattage resistor in series with the sensor to set the current level and avoid shorting the power supply. Another voltage regulator will be placed in series before connecting to the PIC controller. This will ensure that the
11、 appropriate high voltage of 5 V is seen by the controller.Sensor #1Our first rain sensor will consist of a thin sponge-like material between two copper conducting plates. The plates will be insulated on the other five sides as a safety precaution. When this sensor is placed on-end on top of the veh
12、icle, rain water will saturate the sponge and allow current to flow from one conducting plate to the other through the water in the sponge. We may also use a funnel to focus water onto the sponge. We will experiment with different types of sponges until we find one that functions well for the sensor
13、. The input to this sensor will be the supply voltage. The output will be a voltage sent to the microcontroller, representing a logical 1 or 0. Sensor #2Our second rain sensor will again consist of two copper conducting plates covered with insulation on five sides. The plates will be in contact duri
14、ng dry conditions, allowing current to flow. A piece of super-absorbent clay will be placed underneath one of the plates with a funnel directing rain water to it. When wet, this clay material will expand enough to push up on the plate above it and break the circuit. This will then trigger a response
15、 in the microcontroller. As the clay dries, it will shrink back to its normal size, and the plate will fall back into place.Again, the input to this sensor will be the supply voltage. But unlike our first sensor, the second sensor outputs high voltage when dry and low voltage when wet. Therefore, we
16、 will connect an inverter between the sensor and the PIC controller.Sensor #3Our third rain sensor will consist of a circuit etched onto an insulating PC board. The circuit will be a network of lines resembling clasped hands. Under dry conditions, each conducting line on the board will be too far fr
17、om its neighbor to complete the circuitbut by a small margin. With even a single drop of rain virtually anywhere on the board, current will flow through the water to complete the network. Due to the high sensitivity of such a sensor, it is likely that we will use several if we use any. Our microcont
18、roller will power the window motors only if most or all of the sensors are detecting rain. Alternatively, we may simply decide on a model that spaces these conducting lines further apart. We will examine the impact each setup has on detection response time and reliability. In either case, the third
19、sensor will be setup in our detection system in the same fashion as the first sensor. A non-zero voltage will be sent through the voltage regulator and to the PIC controller when rain is detected.Microcontroller The Microcontroller block will form the heart of the project. The sensors, override cont
20、rol switch and the motor blocks will all connect to the Microcontroller block. This block will basically be comprised of a PIC controller used to read in the sensors and implement the override switch to control the Motor block. Additionally, we might use this block to set a timer on how long the mot
21、or should run in order to fully roll up the windows. This will be a safety/power saving feature for the power windows. User InterfaceThe User Interface block consists of a single switch which turns the rain detection system on or off. The switch will interface with the microcontroller, but will be s
22、eparate and located near the driver seat so that the driver can access it while driving. The switch will have to be in the ON position for the system to function, and will override any actions taken by the system if turned to OFF at any time. It will also contain LEDs to indicate that the system is
23、ON, OFF, and working.Vehicle InterfaceThe Vehicle Interface block consists of a direct parallel connection to the electronic power window system. This block is controlled by the microcontroller. Since the connection will be in parallel, all other functions of the power window system will not be affe
24、cted. Further research is still required to determine where these connections will be made.III. Verification1. Testing Procedures: We will test our blocks individually in order to aid in debugging.SensorsOur sensors are probably the most critical components in our design. It is very important that w
25、e can be confident in their ability to consistently detect rain in a timely matter. The basic setup we will use to test each of our sensor modules will be as bare as possible. We will supply a voltage to one end of each sensor and measure the voltage and current immediately on the other end. If we m
26、easure a significant amount of current (or insignificant amount of current in the case of sensor #2), we can be sure that the sensor is detecting correctly. Even if some voltage is dissipated across the sensor, we can use our voltage regulator to regenerate the signal if need be. At first, we will m
27、ake sure to limit the current output from the power supply to ensure that we are not passing a damaging amount through our resistor, sensor, or voltage regulators.We will try out a few different methods to simulate rain in the lab. To simulate light rain conditions, we may simply use a dropper full
28、of water. To simulate heavy rain conditions, we may pour water through a strainer held above our sensor. Eventually we will test the effectiveness of our sensors under real rain conditions.Voltage RegulatorsTesting the functionality of our voltage regulators is another important step. This will help
29、 us avoid damaging our equipment by feeding in too great a voltage. We will test them by inputting the full range of voltages each may realistically see, including voltage spikes. We will measure the output voltage with a multi-meter to ensure that it will be accurate and stable when the voltage reg
30、ulator is plugged into our detection system.MicrocontrollerFor the Microcontroller block, we will be using power supplies to act as sensors and the override switch in order to simulate all possible combinations of inputs. We will hook up an oscilloscope on the outputs, which would normally connect t
31、o the Motor block, and check to see if the outputs match up to the minimum/maximum specifications of the Motor block.User InterfaceThe switch will need to override the system at any point of operation. Tests that will be performed with the switch are:- Making sure the system only functions while the
32、 switch is in the ON position- Turn the switch to the OFF position while rain is being detected and the windows are closing and make sure the windows stop closing- Test whether the switch functions correctly while vehicle is running and while the vehicle is not running- Test how long it takes for th
33、e system to shut down when the switch is turned to the OFF position, needs to be almost instantaneousVehicle InterfaceTesting will begin by using two Bosch window motors, to account for the right and left car windows. A 12 V power supply will be used to simulate a car battery. These motors will be p
34、owered by the 12 V supply and will have to run at the correct speed and for the correct amount of time, which is yet to be determined. Once this is functioning correctly, the system will be implemented into a vehicle and tested with the actual car battery. Once implemented into the vehicle, the othe
35、r functions of the power window system will be tested for functionality. 2. Tolerance Analysis:The most relevant factor in our system is the sensor and its tolerance when it comes to detecting rain. Our goal is to successfully detect rain as soon as possible without building a sensor so sensitive th
36、at it falsely detects rain. Also, wed like to build a sensor with a fast turn-around time, so that it doesnt remain wet for hours after the rain has stopped, unable to detect whether or not it is still raining. With these tolerance guidelines in mind, we will set out to create a detection system cap
37、able of rain detection within 20 seconds of drizzle, within 10 seconds of light rain, and within 5 seconds of heavy rain. Our system will also “dry out” within 30 minutes of the rain stopping. To meet both of these tolerance requirements, we may employ multiple types of sensors: one sensor to detect
38、 rain and one sensor to detect a lack of rain.IV. Cost and ScheduleCost Analysis:PartQuantityPrice Estimate/UnitTotalPIC Microcontroller1$4.00$4.00Variable Voltage Regulator2$1.50$3.00High Wattage Resistor1$0.40$0.40Copper Plates8$3.00$24.00PC Board1$1.00$1.00Sponge1$5.00$5.00Wire (15 ft.)1$3.00$3.0
39、0Sodium Bentonite Clay 1$10.00$10.00Switch Module1$3.00$3.00LED3$0.25$0.75Custom Plastic Module5$10.00$50.00Circuit Breaker1$1.00$1.00Total$105.15Labor: ($30/hr)*(2.5)*(15 hrs/week/engineer)*(12 weeks)*(3 engineers) = $40,500Part Total + Labor = $105.15 + $40,500 = $40,605.15Schedule:WeekRobChintanB
40、rian11-SepResearch power window setupPIC Controller logic designAcquire part numbers18-SepSensor 1 design and schematicSensor 2 design and schematicSensor 3 design and schematic25-SepDesign Review compilationProgram PICOrder parts, Pick-up simple parts from hardware store2-OctBuild and Test Sensor #
41、1Build and Test Sensor #2Build and Test Sensor #39-OctTest and Modify Sensor #1Test and Modify Sensor #2Test and Modify Sensor #316-OctCompile and wire modules, and test23-OctTroubleshooting30-OctImplement to car6-NovTroubleshooting and work on Final Paper13-NovWork on presentations and prepare Demo20-NovFinalize paper, presentation, and demo
