Instrumentation

From Trevipedia

The electrical system of the car is organised as a number of subsystems. To simplify the wiring, a (0, 12 V) power bus is used to supply power to each of the subsystems, and a CAN serial communications bus is used to send control messages and data between subsystems.

The subsystems include:

• battery
• motor control
• front lighting (left and right)
• rear lighting
• dash
• driver controls

Dash

The UniSA prototype used a telematics computer dontated by Freescale to provide dash functions. The computer ran embedded Linux.

Team Trev is currently using an AMOS-3000 computer with a 7" daylight-readable LCD display. The operating system is TinyCore Linux. It takes about 10 seconds to boot and start the dash software, which is not quite fast enough.

The dash software is written in Processing.

The AMOS-3000 / TInyCore / Processing system was not fast enough to process CAN messages, so Team Trev used a small microcontroller to extract dash data from the CAN bus; the dash requested data from the microcontroller as required, via a RS-232 port.

The colour screen provides information including:

• telltales: left indicator, high beam, battery low, handbrake, right indicator
• warning messages: low cell voltage, high cell voltage, battery temperature, motor temperature
• speed
• odometer
• battery measurements: power, current, discharge, temperature low cell voltage, high cell voltage.

Buttons surrounding the screen were used to control the lights.

A key advantage of using a computer is that it is easy to customise the display and to interface to other subsystems—battery, motor controller, lighting controllers and external switches.

The following image is a screen-capture from an early version of the dash software:

The next image shows telltales along the top, and warnings along the bottom:

Indicators and horn

The UniSA prototype used momentary-on push buttons on the steering wheel to control indicators and horn. This was easier to implement than a conventional indicator stalk, and user testing showed that it was easy to use. However, it did not provide self-cancelling indicators.