Multiplexing For Vehicles



Posted: Sunday, May 17, 2009

by Rick Ballester
ECX

Why is multiplexing an integral part of car nowadays? With every new car model that comes out there seem to be more useful gadgets and luxuries that simplify our lives, yet car sizes arent growing to accommodate everything that is being packed in them now. This is all due multiplexing.

The term multiplexing describes the manner in which different pieces of equipment are electrically interconnected to send and receive signals to one another using a data bus.

A data bus consists of a group of 2, 3, or 4 wires that connect one piece of equipment (module) #1 to module #2 and then continues to module #3 and so on. It is through these wires that all modules send and receive signals to one another. The signals transmitted indicate to the corresponding piece of equipment what function it must perform at any given time. For example, module #1 may consist of a group of switches. When one of them is actuated, it may indicate to module #2 (which could be a motor) that it must start running. Another switch in module #1 might be used to tell module #3 (which could be a light) that it must turn on or off. Since there is only one data bus linking all of these pieces of equipment, each command must be transmitted one at a time to avoid confusion. This technique of sending multiple command signals over a single data bus is called time division multiplexing (multiple commands are sent and received among multiple devices one at a time).

A good illustration of multiplexing is the drivers side door on your car. That module on your car door controls your power windows, locks, and side mirrors. Instead of having numerous wires to control every function of each button, they are connected to a data bus which transfers data between components connected to it.

Multiplexing allows fewer wires to be required for each system function, which means smaller wiring harnesses, reduced car weight, improved installation, and reliability. Accessories and vehicle features and be easily added to the vehicle through software changes.

This technique is relied upon heavily for emergency vehicles due to the numerous components, the cabling required for them, and the confined space. ECX Electronics provides a variety of multiplexed modules designed to perform the functions required in these vehicle. To optimize the reliability of the system, these modules communicate with each other using a peer-to-peer multiplexing technique (each module can talk and or listen to all the other modules) which does not require a master control device.

Please visit http://www.ecxelectronics.com for more information

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