Preliminary Design Report January 28 th, 2012

Transcription

1 EEL 4924 Electrical Engineering Design (Senior Design) Preliminary Design Report January 28 th, 2012 Project: BlueSky (Digital Skydiving altimeter and freefall computer) By: William McKaba

2 BlueSky Page 2. Table of Contents: Project Abstract 3 Project Features 4 System Components 6 Technical Objectives 8 Flow Chart 9 Gantt Chart 10 Figure 0.) Altitude check while skydiving 3 Figure 1.) BMP085 - Digital pressure sensor 6 Figure 2.) ADXL335 3 axis accelerometer 6 Figure 3.) D2523T- GPS smart antenna module 7 Figure 4.) CFAH2002Y-PDI-ET 2x20 Character LCD 7 Figure 5.) PIC18F4550 Microcontroller 7 Figure 6.) Block Diagram 9 Figure 7.) Gantt Chart 10

3 Project Abstract: BlueSky Page 3. I plan to build a digital altimeter for skydiving that will be capable of analyzing and reporting data from each skydive as well as triggering an alarm for when to pull the parachute. The data recorded will provide the skydiver with valuable information from their skydive with which they can use to analyze and improve their skydiving performance. The system will be small enough to fit comfortably on a person s wrist and not interfere with the person s ability to skydive. It will be relatively inexpensive and will have a user friendly LCD and push button interface. Figure 0.) Altitude check while skydiving

4 Project Features: BlueSky Page 4. There will be four modes of operation for the system: GROUND, CANOPY, FREEFALL, and AIRPLANE. These modes of operation will distinguish between the different necessities of the device in order to preserve battery life. Each mode will be automatically detected and will incorporate a different functionality of the system. Below is a description of the functionality for each mode of operation. GROUND Mode: While on the ground, the system will display the current mode, the battery life and will also prompt the user to enter the altitude at which to generate the alarm. After the user has entered the alarm altitude, the system will display the alarm altitude selected. The display will maintain this screen until either another button is pressed or another mode of operation is detected. AIRPLANE Mode: When flying in the airplane up to the exit altitude, the system will display the current mode, the battery life, the current altitude, and the alarm altitude. The system will run a timer module during the extent of AIRPLANE mode and record how long it took to climb to exit altitude. The user will be able to change the alarm altitude during the flight if necessary. The system will remain in AIRPLANE mode until it detects that the skydiver has exited the plane.

5 FREEFALL Mode: BlueSky Page 5. When the skydiver exits the plane, the system will detect the exit and switch to FREEFALL mode. The system will then continuously update and display the current altitude on the LCD. During the extent of this mode, the system will constantly be processing altitude, position, acceleration and time. These processes will provide data to calculate freefall time, maximum fall rate, minimum fall rate, maximum glide ratio, when the alarm needs to activated, and what altitude the parachute was actually pulled at. When the specified alarm altitude has been reached, LEDs will blink on and off to signal the skydiver to pull the parachute. The system will remain in FREEFALL mode until it detects that the skydiver has pulled their parachute. CANOPY Mode: When the skydiver pulls his parachute, the system will detect the change in acceleration and switch to CANOPY mode. The LCD will continuously display the current altitude. A timer will run throughout the extent of CANOPY mode to determine how long the skydiver was under canopy before landing. The system will remain in CANOPY mode until it detects that the skydiver is on the ground at which time it will switch back to GROUND mode.

6 System Components: BlueSky Page 6. The main considerations for choosing components were size, accuracy, sensitivity, power consumption, communication interface, and cost. Figure1.) BMP085 - Digital pressure sensor ($9) Figure 2.) ADXL335 3 axis accelerometer ($10)

7 BlueSky Page 7. Figure 3.) D2523T- GPS smart antenna module ($80) Figure 4.) CFAH2002Y-PDI-ET 2x20 Character LCD - ($13) Figure 5.) PIC18F4550 Microcontroller ($12)

8 Technical Objectives: BlueSky Page 8. The system will have to perform several complicated tasks within small timeframes. The altitude will be read from the pressure sensor via SPI on the PIC more than once every second when airborne. The LCD will be updated each time the altitude is processed. The system will need to display accuracy in altitude of 100ft so an update will need to occur at about 5Hz. The GPS receiver receives data at 5Hz and outputs standard format NMEA strings over the TTL/UART pins with a 9600 baud rate, 8 bits, no parity, and 1 stop bit. The data will be processed to determine and compare glide ratios every 500ft of freefall. Timer modules will be used to calculate time in seconds. The accelerometer will be processed by three ADC inputs on the PIC. When the parachute is pulled, the voltage spikes should be considerably greater than all other motion leading up to that point. The altitude alarm will alert when the altitude reading from the pressure sensor is within the specified range for the deployment altitude.

9 BlueSky Page 9. Block Diagram: Figure 6.) Block Diagram

10 Gantt Chart: BlueSky Page 10. Gantt Chart of Project Design Progress and Procedure Throughout the Semester Preliminary research Order parts Prototype Debug Test Debug Design PCB Construct PCB Test Debug Final improvements Debug Presentation K+P Figure 7.) Gantt Chart