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EL-23 June 6, 1997

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Electronic Control of Vehicular Electrical Subsystems

Contributor: David H. Cowling

Affiliation La Tech University

Address: Electrical EngineeringPO Box 10348 T.S.

Ruston, LA 71272

Phone: (318) 257-2857

Fax: (318) 257-4922

Email: cowling@engr.LaTech.edu

Type: Design Project

Student Time: Three to Six Weeks

Location: Classroom, Laboratory, Library, Home

Summary

This project calls for the redesign of the electrical system in an automobile by the

replacement of the wiring harness with a power bus and a signal bus. Electrical wiring

harnesses in automobiles universally carry power in parallel from the activating switches in

the drivers compartment to the actual subsystems which are to be controlled. Hence the

activating signal for an electrical subsystem and the power for this same subsystem are

carried over the same wire. This causes wiring harnesses of automobiles to be both

complex to design and at the same time bulky to route throughout the automobile.

This design project calls for the development of an electrical subsystem control for anautomobile where the power is routed over a single power bus and the control signals are

routed separately over a signal bus.

ABET Descriptors

Engr Sci Content: Electrical Circuits, Analog Electronics, Digital Electronics

Type: System, Subsystem, Component

Elements: Synthesis, Analysis, Construction, Evaluation

Features: Design Methodology, Creativity, Open-ended

Constraints: Reliability, Cost, Safety

Effort: Team

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Electronic Control of Vehicular Electrical Subsystems

This project calls for design and the development of a new method to control the various

electrical subsystems of an automobile. The parallel power/signal wiring harness that is

connected to switches at one end and to the controlled subsystem at the other should be

replaced by a power bus and a signal bus. Electronics should be designed for this control

process.

This design should be determined by cost, complexity, service requirements, reliability,

and safety.

The final results of this design should include the following:

Documentation

a) Schematic diagram of a prototype control system.

b) Wiring diagram of the Power Bus and the Signal Bus.

c) Signal coding and decoding chart for each of the controlled functions.

Hardware

a) Prototype system set up to take two input signals (switches) and

control two electrical subsystems.

b) A prototype power and signal bus.

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Electronic Control of Vehicular Electrical Subsystems

Engineering Notes:

This project should yield a carefully thought-out digital design. The power bus should

provide power to operate both the electronics and the subsystems. The digital control

signals should be routed down a separate twisted pair (or coaxial cable). Both the signal

bus and the power bus should route in parallel through each of the controlled subsystems.

Student groups involved in this project should spend time researching the actual

requirements for the subsystems on the vehicle. They should then follow this with

methods of coding and decoding digital signals. The system is to be designed for the

complete automobile and a prototype system is to be built for two inputs and two outputs.

Objectives/Comments:

The objective of this project is to lead the student through a series of investigations of the

requirements for vehicular subsystems and the present methods by which this is

accomplished. The design groups should then extend this by employing electronic

(probably digital) signaling over a signal bus for the control of these subsystems. The

design should include both the signal receiver and associated control circuit as well as the

coding transmitter. This project is also open ended in the sense that one might place only

two multi-function receivers (one at the rear and one at the front of the vehicle) with a

single multi-function transmitter (at the dashboard). The other extreme would involve a

separate transmitter and receiver for each switch and subsystem.

Expected Outcomes:

This project should help with a student's ability to find information. This project should

also lead to the examination of a problem more creatively. In addition knowledge from

electrical circuits, analog electronics and digital electronics will be required and expanded.