All modern cars have a computer, in charge of monitoring the various systems. This central computer receives information from a collection of sensors that monitor things like oxygen, air pressure, air temperature, and engine temperature, to name a few. Using this information, the computer can control the car's parts to get the best performance from the engine while keeping emissions low.
How do these sensors work? It depends on whether they are pressure sensitive or light sensitive. A pressure sensitive device can sense changes in pressure and emits an appropriate voltage in response to correct problems. These sorts of sensors are used in braking systems and collision avoidance systems, for example.
Light-sensitive, or optical, sensors work very much like the wireless mouse technology in desktop computer systems. A small diode bounces light off a surface onto a sensor to form images. The sensor sends the data to a digital signal processor for analysis. This processor can detect patterns in the images and figure out how they have changed since the previous image it received from the sensor. Based on the changes in patterns over time, the processor can determine how far the mouse, or car, for example, has moved. It can then send electrical signals to the central computer to trigger the appropriate response.
For instance, sensors can scan the precise position of the driver's eye level and adjust the seat accordingly. Newer prototype cars include infrared light enhancers to improve night vision, as well as rearview mirrors and rear bumper sensors to alert the driver when other vehicles are approaching the car's blind spot. Adaptive headlamps contain sensors that monitor a car's speed and steering wheel movements and adjust lighting accordingly. For example, at high speeds, light beams are given a longer reach. Remain-in-lane systems use forward-facing cameras to monitor the car's position in relation to the road's centerline and side marker lines for 20 meters ahead of the car. If the car begins to veer out of the lane, the sensors detect this and set off a warning sound.
The automatic door openers found in most grocery stores use a very simple form of radar. The box above the door sends out bursts of radio waves and waits for the reflected energy to bounce back. When a person moves into the field of wave energy, it changes either the amount of reflected energy or the time it takes for the reflection to arrive, and the box opens the door. Infrared security systems work in much the same way, replacing the radio waves with infrared light waves.