GPS SENSOR

Team Members: Benjamin Copeland, Brian Greer, Scott F. Horowitz, Devon G. Williams
Faculty Adviser: Liz Kisenwether
Project Sponsor: Timothy Wheeler
Sponsoring Company: PSU SPIRIT Rocket

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Project Overview
  The SPIRIT (Student Projects Involving Rocket Involving Techniques) Sounding Rocket Project is a long-duration research project designed for undergraduates. SPIRIT II will be launched in November, 2002, and its purpose is to measure wind current velocity in the mesosphere.
  Our project was to take a commercial GPS receiver module, interface it with a transmitter, power the module and interface board, and construct a packaging to house all boards. We also had to write an introductory self-paced module for future SPIRIT projects about GPS.

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Project Constraints

• Total Package must have a maximum mass of 100g
• Must run for a minimum of 50 minutes
• Must withstand rigors of launch and descent

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Project Implementation

• Interface Board
    The purpose of the interface board is to connect the power supply to the 12-Channel ALLSTAR GPS receiver, connect the transmit line of the GPS receiver to the transmitter, and to connect the appropriate pins on the GPS receiver to required voltage signals. We used Orcad’s Capture and Layout software to design and prepare the interface board for fabrication. The fabrication was performed by Advanced Circuits of Denver, CO.
    Testing of the voltage regulator indicated that a minimum input voltage of +7 VDC was required in order to obtain +5 VDC from the output. This voltage requirement is due to the voltage drop across the diode in the voltage regulator and will necessitate the use of three 3 V batteries connected in series.
  The Interface Circuit Diagram
  The PC Board Layout
  
  
• Packaging
    The package will be constructed from blue-board Styrofoam and coated with Kevlar resin. The foam walls will be grooved on the sides to support the three circuit boards: GPS receiver, interface board and transmitter. The back end of the package will be a single sheet of Styrofoam applied flush to the composite center. On the front side of the package, the top and bottom layers will extend out an extra ½”. Four plastic tabs will extend out ¾” and will be placed inside the grooves. The front piece will have four holes to fit the tabs, which will extend a ¼” out when the front piece is in place. A vertical hole in each tab will hold a pin that will hold the front piece in place. Thus when assembled the front piece will be held between the top and bottom layers and the four pins will keep it flush to the composite center. The composite center and back piece will be adhered together by epoxy, and this piece will be coated in Kevlar. The front piece will be coated with Kevlar separately from the composite center and back.
  The Package Design
  
• Power
    Three Lith-41 3V batteries will be assembled in series to achieve the required voltage. With the GPS receiver requiring a minimum discharge current of 250mA, this battery generates a maximum discharge current of 1000mA and has a nominal capacity of 750mAh. Based on the battery specifications, the total mass is 33 grams and the batteries have been tested to last at least 90 minutes, which is sufficient for the requirements of our project.
  The Lith-41 battery
  

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Related Materials

Proposal
Preliminary Design Review (Power Point)
Critical Design Review
Training Module