Cars have progressed a long way from the time when a humble eddy-current electromechanical speedo was the only instrument in view. These days, many instrument panels feature LED, LCD and TFT displays – and even conventional-looking dials have stepper-motors driving the needles.

Instrument clusters

Rather than displaying just fuel level, coolant temperature, speed and engine RPM, instrument panels can now display literally hundreds of discrete parameters. These include trip computer information, GPS navigational information, time, outside temperature, selected radio station, cruise control action, gear position, date, door openings, service intervals, oil level and quality, warning lights and text messages.

Fig.1: block diagram of a typical current-model instrument cluster. A microcontroller dominates and is used for signal acquisition, filtering, diagnostic functions and for driving warning lights and stepper motors. It also performs the calculations that allow the display of speed, service intervals and oil quantity. [Bosch]

Fig.1 shows the block diagram of a typical current model instrument cluster. As can be seen, a microcontroller dominates and is used for signal acquisition, filtering, diagnostic functions, and for driving warning lights and stepper motors. It also performs calculations that allow the display of speed, service intervals and oil quantity.