Computer Questions: How Car Computers Work

How the computer of a car works. A guide to the complicated systems within a car.

As the years go by, the makeup of cars become more complicated. Today cars may have as much as 50 microprocessors in them. The increase in the number of microprocessors is in part because of advanced diagnostics, new safety features, new comfort and convenience and simplification. These factors and many more are what make the design of cars better.

It was possible for car engines to be built without microprocessors before emission laws were passed. With the enactment of the stricter emission laws, more sophisticated control themes were required to make the air/fuel mixture regular so that pollution could be removed from the exhaust using the catalytic converter. Controlling the engine is the most import processor job on a car. The most powerful computer on most cars is the engine control unit. The engine control unit uses closed loop control to manage the engines emissions and fuel economy. The engine control unit is very important and it uses calculations and date to make sure that the car gets the lowest emissions and best mileage.

The engine control unit is packaged with many other components that support the processor. The analog-to-digital converters are devices that look at the outputs of some of the cars sensors. Because the processor only understands digital numbers, the analog-to-digital converter changes the voltage into 10-bit digital numbers. High-level digital outputs are required for the engine control unit to fire spark plugs, open and close fuel injectors and turning the cooling fan on and off. The digital-to-analog converts digital numbers into an analog voltage. This is needed because the processor is a digital device and sometimes the engine control unit has to have an analog voltage output to drive some of the components. Signal conditioners are circuits that adjust the level of the signals that come in or out because at times inputs or outputs must be adjusted before they are read. Communication chips are chips that scan the many different communication standards that cars use. Many standards are used but the one most frequently used is CAN (controller-area-networking), it allows for connections speeds of up to 500 kbps making it much faster than older standards. Faster speeds are becoming more and more necessary.

The new communication standards have made the designing and building of cars easier. One of the advantages of a communication bus is that each module can let the central module know about faults, which stores them and communicates them to an off-board diagnostic tool. This is useful so that technicians can diagnose problems with the car. It is especially good with intermittent problems because they are notorious for disappearing as soon as you bring the car in for work.

Microprocessors and communication standards have made cars much easier to design and manufacture. A good example of these simplifications is the instrument cluster of the car. The instrument cluster gathers and displays data from different parts of the vehicle. Most car manufacturers get the instrument clusters fully assembled from the supplier. The suppliers make them to suit the car manufactures specifications. Communication standards such as these make it uncomplicated and worry free for car manufactures to outsource the design and manufacture of their cars.

Now clusters are being used for sensors on a smaller scale. Sensor manufacturers are now making smart sensors that are integrated with all of the electronics as well as microprocessors that allow it to do such things as read voltage. Another smart sensor advantage is that the digital signal traveling through the communications bus is less vulnerable to electrical noise.

Communication buses and microprocessors also assist in the simplification of wiring by using multiplexing. Because more and more devices are being added to cars, multiplexing is important so that the wiring stays in control. A multiplexing system is a system that has a module containing at least one microprocessor that consolidates the inputs and outputs of a certain area of the car. An example of such a system is a drivers-door module. The drivers-door module is where there are a lot of controls on the door, such as power-window, power-lock, power-mirror, and power-seat controls. The drivers-door module is practical because it monitors all of the switches rather then running a thick bundle of wires from the system out of the door.

Now that new safety systems have developed, the number of microprocessors in cars has increased. Over the last ten years air bags and anti-lock brake systems have become very common in cars. Other safety features such as traction-control and stability control are also becoming more common. As each new system is added, a new module is added to the car. These new modules contain multiple microprocessors. In the future, as new safety features are added, more modules will be added to cars.

In the next few years, there will be more and more convenience features added to cars. Each of these new features will require more electronic modules, which contain multiple microprocessors. There seems to be no limit to how much manufactures are going to put into cars.

© High Speed Ventures 2011