Nearly everything seems to be embedded - here are some of the most common embedded systems used in everyday life:
navigation systems badge readers crock pots PDAs battery chargers cameras elevators MP3 players patient monitoring systems clocks smoke detectors TVs coffee makers thermostats DVD players keyboards ultrasonic toothbrushes curling irons vending machines cell phones internet servers cash registers cordless phones printers microwave ovens ceiling fans hot tubs ATMs garage door openers parking meters refrigerators
Examples of multiply-embedded systems
Some devices and products have MORE THAN ONE microprocessor in them. Take a new car for example - how many embedded processors does it have?
Survey says ...
automatic transmission antilock brakes DVD player automatic headlights and high beams emission controls child-proof locks tire pressure detection systems GPS navigation garage door opener the infamous "check engine" light automatic stability control radio sensor checks (oxygen, temperature, oil level, etc) sunroof keyless entry memory for seats and mirror settings cruise control heated seats dashboard display (speedometer, odometer, etc) climate control airbag control
Reactive Embedded Systems
Some embedded systems are called "reactive" systems because they react to conditions in their environment. These are similar to the sensors in a car to detect when the engine temperature goes too high, but these are often even more hidden from the average person.
These systems detect external conditions and react to changes in these conditions. Reactions may be to record data (such as temperature, vibration, weight, position), to sound an alarm, to turn on or off motors or devices, or to send messages to other processors. They often act as sentries (e.g., alarm systems) and monitors. An interesting one can detect and record extreme shocks in vibration and temperature. The devices are often strapped to shipping containers to record when a shipment may be damaged in transit.
So what makes these things embedded?
Before, we talked about the brains inside the device. And how these brains can be specifically designed just to run the functions needed. For example, your washing machine doesn't need to do floating point match and download streaming video, and your ultrasonic toothbrush doesn't need a color display. So don't spend money on a microprocessor that does more than you need.
The low end microprocessor are dirt cheap in quantity - practically free for a high volume product. These are 4-bit and 8-bit micros that would load Windows XP in a brisk 30 minutes (as if a 32-bit operating system could run on an 8-bit micro, but you get the idea). But who needs Windows when you just need to check a few sensors, scan for a radio station and adjust the side mirror? So heck, make everything configurable with its own little brain!