SCHOOL BUS ALERT SYSTEM

RF DESIGN TEAM



Michelle Montoya


Joaquin Arreola


Mohammed Al-Rubaian

Abstract

Bradley Contractors Inc., located in East Texas, has decided to take the initiative in developing a system with the capability to warn their logging truck drivers of the potential danger of school buses operating in the area.

Logging trucks operate on rural highways and back roads in order to transport raw materials to the mills for conversion into lumber and other products. It is not unusual for the trucks to be on the road during early mornings and under foggy conditions. School buses also operate under these conditions and exhibit frequent stops along these rural highways. It is very difficult for a fully loaded semi-truck to slow down when approaching a slow moving or stopped school bus. The conditions listed above provide a high potential for serious accidents and thus injury to a significant number of children.

Currently, there is no system available to help forewarn the logging trucks of the upcoming danger. Mike Olivas, an employee of Bradley Contractors Inc., has expressed the need of a system to aid in this problem. The RF Design Team, at the University of Texas-El Paso has taken on the challenge to meet the desired requirements. The system will alert the truck drivers of the bus approaching just over the next hill or around the next corner. This will greatly reduce the risk of potential accidents along these rural highways.

Bradley Contractors desires a system that can provide the services listed above. This would produce a safer environment to their community as well as improving the efficiency of the raw material transportation process.

Objectives

1.   Design a transmit/receive system to alert logging truck operators of oncoming buses.

2.   System should have the capability of locating a bus within .25 of a mile in front of the truck.

3.   Receiver is to be mountable inside the trucker's cab and have LED alerts as well as audible alerts.

Factors and Conditions

1.   Production cost within the $250 range for both the transmit and receive units.

2.   Operate at efficient frequency through foliage and mountainous terrain.

3.   Operational through adverse weather conditions such as extreme heat, rain, fog and hail.

4.   Designed to incorporate very little user maintenance.

Major Components

RF Design Team has designed the desired transmit/receive system using these components:

1.   DeLorme GPS Tripmate

2.   BS2-SX micro-controller

3.   PAK II Math Coprocessor

4.   XC-2 DTMF to ASCII transceiver

5.   RF audio transmitter & receiver

6.   Whip antenna

Bus Transmitter Operation

The school bus holds the transmitter module for the Bus Alert System. The compact unit is powered using 13.8 Vdc provided from the bus' battery. The following is a description of the operation of the bus transmitter.

The bus' coordinates (latitude and longitude) are obtained using the GPS Tripmate which will be referred to as GPS-A data. The GPS unit provides NMEA formatted data which is a form of ASCII data. This ASCII formatted data is sent to the DTMF encoder/decoder transceiver. At this point, the DTMF acts as an encoder and converts the ASCII data into audible tones.

These audible tones are then sent to the RF transmit/receive module. The RF unit works as a transmitter and sends the audible tones through the omnidirectional whip antenna at a frequency of 433 MHz.

Truck Receiver Operation

The receiver module is located inside the truck's cab and is also powered by 13.8 Vdc from the battery. The following is a description of the operation of the truck receiver.

The transmitted audible tones are received using the same omnidirectional whip antenna and RF unit. These audible tones are then sent to the DTMF transceiver where they are converted back to ASCII. The bus' coordinates are then sent to the Basic Stamp II-SX (BS2-SX) micro-controller.

The receiver is also fitted with a GPS Tripmate. This unit provides the coordinates of the truck in ASCII format which will be referred to as GPS-B data. The truck's coordinates are also sent to the BS2-SX.

At this point, both the coordinates are inputted into a distance calculation program. The program is designed to calculate the shortest distance between two points using latitude and longitude coordinates. The PAK II math coprocessor is integrated into this process due to its capability of calculating floating point numbers as well as sin/cos functions. Once the distance has been calculated, the BS2-SX will drive the LED alerts as well as the audible alerts accordingly. 

Issues

The system design has included a great deal of correspondence between Mike Olivas and our RF Design Team in order to ensure all requirements are met. Since East Texas is a significantly different environment than any of our team members are use to this has proven to be very beneficial.

The system has been designed to meet production line requirements.  It was the goal of our team to provide a product that will be easiest for the manufacturing engineer to produce. This entails the use of already made components and very little in-house board level design.

Mike Olivas has been informed of all aspects of the Bus Alert System. He is aware of the success of the RF Design Team as well as any discrepancies that have been encountered.

Major Components

GPS TripmateBasic Stamp II RF Transceiver

Conclusion

    The RF Design Team has successfully completed the initial prototype as required by Senior Project II at the University of Texas at El Paso. All major components have been tested and integrated into the designed system.

    A great deal of progress has been made this past school year and the RF Design Team feels that this initial prototype is only the first step in the goal of Bradley Contractors. One of the major problems faced by the RF Design Team was to reach the desired production cost range of $200-$250. This final design can be re-engineered in order to bring down production costs.

    In conclusion, the RF Design Team has created the prototype desired by Mike Olivas and Bradley Contractors. Due to the time frame, the RF Design Team has run out of time to make this system even more successful.