Automotive Electronics
Automotive engineers were slow to adopt electronics applications because the cost was high compared to the benefits to consumers. Electrical systems were also very limited in the beginning. A starter on a 1912 model was the first electrical device used on an automobile. Electric headlights and horns followed quickly and replaced dangerous lanterns and bulb-type horns. By 1930, the six-volt electrical system was standard to most American automobile makes. The key electrical components at that time were the battery, the starter or cranking motor, the generator (also called a dynamo), the ignition system, the lighting system, and power for accessories and controls.
By the mid-1950s, 12-volt systems replaced the six-volt standard. After World War II, engine speeds and cylinder pressures increased, so the voltage demands for ignition were much greater. Manufacturers also provided a wider range of accessories such as multispeed windshield wipers, radios, and power windows. To ignite fuel, a much higher voltage of about 20,000 volts is needed. The ignition system forms a circuit that routes from the battery through the ignition switch, the ignition coil (an induction coil that increases voltage), a circuit breaker, and back to ground. The circuit breaker or interrupter switch develops high voltage across the secondary coil of the ignition; the coil transfers power to the distributor which connects the coil to each of the spark plugs to cause combustion.
The generator feeds electricity to the lighting system, controls, and accessories. The engine crankshaft drives the generator through a belt system. The generator produces electric power, but a voltage regulator balances the electrical needs of the whole system including the requirements for keeping the battery charged. The regulator also provides this balance regardless of the engine speed. When the generator (a direct-current device) can't carry the electrical load, an alternator (using alternating current) furnishes the added charge. Alternators were made available in 1958 when the number of electrically powered accessories began to tax the generator's capacity. The battery stores excess energy so power can be provided to start the engine or operate accessories when the engine is turned off. Power is also drawn from the battery during operations when the generator speed is too low.
The first electronic devices in automobiles were radio receivers that became standard equipment in the 1930s and 1940s. Manufacturers attempted to introduce electronic ignition and fuel injection systems in the late 1950s, but costs were prohibitive and the public saw little advantage to these options. In the 1970s, however, the regulations restricting exhaust emissions made ignition and fuel injection systems necessary. Electronics applications were ideal for these systems because their controls were so precise.
By the 1990s, almost all automotive systems are equipped with sensors and actuators that are linked to electronic control units (ECUs) and an onboard computer. Sensors detect manifold pressure, crankshaft angular position (which controls the timing of both the ignition and fuel injection systems), the ratio of air to fuel that must be optimal iffuel injection and emissions controls are to be effective, and coolant temperature. Other sensors measure exhaust gas oxygen (EGO), which is a direct indicator of other emissions. A "knock" sensor evaluates the rise in cylinder pressure during combustion, which causes an annoying knocking sound in the engine, and retards ignition so stop the knocking.
Critical actuators that are parts of the car's electronics system include the fuel metering actuator that controls fuel metering rods in electronic carburetors, and the exhaust gas recirculator actuator or EGR that links the intake and exhaust manifolds so that exhaust that is high in emissions is recycled through the system until the emissions are reduced. An actuator with functions the driver can observe directly is the cruise control throttle actuator, which adjusts acceleration and throttle motion to maintain the selected cruise speed.
Electronics are being adapted to many other automotive systems. Occupant safety devices like safety belts and airbags are connected to electronic warning signals and actuators. Soon, the driver will be able to monitor low tire pressures, thanks to electronics. Collision avoidance and electronic navigation systems are past initial development and introduction stages and show great promise for linking drivers on the intelligent highway. Speech synthesis devices are being tested so that gauges on the instrument panel can deliver verbal reports to the driver, and "sensor multiplexing" will allow improved coordination of the automobile's devices.
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