cómo funciona una ecu

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Cómo Funciona una ECU http://auto.howstuffworks.com/under-the-hood/trends- innovations/car-computer1.htm Each year, cars seem to get more and more complicated. Cars today might have as many as 50 microprocessors on them. Although these microprocessors make it more difficult for you to work on your own car, some of them actually make your car easier to service. Some of the reasons for this increase in the number of microprocessors are !he need for sophisticated engine controls to meet emissions and fuel"economy standards  Advanced diagnostics Simplification of the manufacture and design of cars #eduction of the amount of wiring in cars $ew safety features $ew comfort and convenience features %n this article, we&ll take a look at how each of these factors has influenced the design of your car.

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Page 1: Cómo Funciona una ECU

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Cómo Funciona una ECU

http://auto.howstuffworks.com/under-the-hood/trends-innovations/car-computer1.htm

Each year, cars seem to get more and more complicated. Cars todaymight have as many as 50 microprocessors on them. Although thesemicroprocessors make it more difficult for you to work on your own car,some of them actually make your car easier to service.Some of the reasons for this increase in the number of microprocessors

are• !he need for sophisticated engine controls to meet emissions andfuel"economy standards

• Advanced diagnostics• Simplification of the manufacture and design of cars• #eduction of the amount of wiring in cars• $ew safety features• $ew comfort and convenience features

%n this article, we&ll take a look at how each of these factors hasinfluenced the design of your car.

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The computer from a Ford Ranger

Sophisticated Engine Controls'efore emissions laws were enacted, it was possible to build a carengine without microprocessors . (ith the enactment of increasinglystricter emissions laws, sophisticated control schemes were needed toregulate the air)fuel mi*ture so that the catalytic converter could removea lot of the pollution from the e*haust. +See ow Catalytic Converters(ork for more details.-Controlling the engine is the most processor"intensive ob on your car,and the engine control unit +EC/- is the most powerful computer onmost cars. !he EC/ uses closed-loop control , a control scheme thatmonitors outputs of a system to control the inputs to a system,managing the emissions and fuel economy of the engine +as well as ahost of other parameters-. athering data from do1ens of differentsensors, the EC/ knows everything from the coolant temperature to theamount of o*ygen in the e*haust. (ith this data, it performs millions ofcalculations each second, including looking up values in tables,calculating the results of long e2uations to decide on the best sparktiming and determining how long the fuel in ector is open. !he EC/does all of this to ensure the lowest emissions and best mileage. See

ow 3uel %n ection Systems (ork for a lot more detail on what the EC/does.

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The pins on this connecter interface with sensors and control devices all overthe car.

A modern EC/ might contain a 4 "bit, 60"7 1 processor. !his may notsound fast compared to the 500" to 8,000"7 1 processor you probablyhave in your 9C , but remember that the processor in your car is runningmuch more efficient code than the one in your 9C. !he code in anaverage EC/ takes up less than 8 megabyte +7'- of memory . 'ycomparison, you probably have at least gigabytes + '- of programson your computer "" that&s ,000 times the amount in an EC/.

ECU Components!he processor is packaged in a module with hundreds of othercomponents on a multi"layer circuit board. Some of the othercomponents in the EC/ that support the processor are• Analog-to-digital converters " !hese devices read the outputs of

some of the sensors in the car, such as the o*ygen sensor. !heoutput of an o*ygen sensor is an analog voltage, usually between0 and 8.8 volts +:-. !he processor only understands digitalnumbers, so the analog"to"digital converter changes this voltageinto a 80" bit digital number.

• High-level digital outputs " ;n many modern cars, the EC/ fires thespark plugs , opens and closes the fuel in ectors and turns thecooling fan on and off. All of these tasks re2uire digital outputs. Adigital output is either on or off "" there is no in"between. 3orinstance, an output for controlling the cooling fan might provide8 : and 0.5 amps to the fan relay when it is on, and 0 : when itis off. !he digital output itself is like a relay . !he tiny amount ofpower that the processor can output energi1es the transistor inthe digital output, allowing it to supply a much larger amount of

power to the cooling fan relay, which in turn provides a still largeramount of power to the cooling fan.

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• igital-to-analog converters " Sometimes the EC/ has to providean analog voltage output to drive some engine components.Since the processor on the EC/ is a digital device, it needs acomponent that can convert the digital number into an analogvoltage.

• Signal conditioners " Sometimes the inputs or outputs need to bead usted before they are read. 3or instance, the analog"to"digitalconverter that reads the voltage from the o*ygen sensor might beset up to read a 0" to 5": signal, but the o*ygen sensor outputs a0" to 8.8": signal. A signal conditioner is a circuit that ad usts thelevel of the signals coming in or out. 3or instance, if we applied asignal conditioner that multiplied the voltage coming from theo*ygen sensor by 6, we&d get a 0" to 6.6": signal, which wouldallow the analog"to"digital converter to read the voltage more

accurately +see ow Analog and <igital #ecording (orks formore details-.

• Communication chips " !hese chips implement the variouscommunications standards that are used on cars. !here areseveral standards used, but the one that is starting to dominatein"car communications is called CA! +controller"area networking-.!his communication standard allows for communication speedsof up to 500 kilobits per second +=bps-. !hat&s a lot faster thanolder standards. !his speed is becoming necessary becausesome modules communicate data onto the bus hundreds of timesper second. !he CA$ bus communicates using two wires.

%n the ne*t section, we&ll take a look at how communication standardshave made designing and building cars easier.

The diagnostic port from a To"ota minivan

Advanced iagnostics Another benefit of having a communications bus is that each modulecan communicate faults to a central module, which stores the faults and

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can communicate them to an off"board diagnostic tool.!his can make it easier for technicians to diagnose problems with thecar, especially intermittent problems, which are notorious fordisappearing as soon as you bring the car in for repairs.'A!auto.com !echnical %nfo 9ages lists the fault codes stored in theEC/ for various carmakers. Sometimes, the codes can be accessedwithout a diagnostic tool. 3or instance, on some cars, by umping two ofthe pins in the diagnostic connecter and then turning the ignition key torun, the >check engine> light will flash a certain pattern to indicate thenumber of the fault code stored in the EC/.?et&s take a look at how microprocessors and communicationsstandards have made cars easier to build.

Easier esign and #anufacturingaving communication standards has made designing and building carsa little easier. A good e*ample of this simplification is the car&sinstrument cluster.!he instrument cluster gathers and displays data from various parts ofthe vehicle. 7ost of this data is already used by other modules in thecar. 3or instance, the EC/ knows the coolant temperature and enginespeed. !he transmission controller knows the vehicle speed. !hecontroller for the anti"lock braking system +A'S- knows if there is aproblem with the A'S.

All of these modules simply send this data onto the communicationsbus. Several times a second, the EC/ will send out a packet ofinformation consisting of a header and the data. !he header is ust anumber that identifies the packet as either a speed or a temperaturereading, and the data is a number corresponding to that speed ortemperature. !he instrument panel contains another module that knowsto look for certain packets "" whenever it sees one, it updates theappropriate gauge or indicator with the new value.7ost carmakers buy the instrument clusters fully assembled from asupplier, who designs them to the carmaker&s specifications. !his

makes the ob of designing the instrument panel a lot easier, both forthe carmaker and the supplier.%t is easier for the carmaker to tell the supplier how each gauge will bedriven. %nstead of having to tell the supplier that a particular wire willprovide the speed signal, and it will be a varying voltage between 0 and5 :, and 8.8 : corresponds to 40 mph, the carmaker can ust provide alist of the packets of data. !hen, it is the carmaker&s responsibility tomake sure that the correct data is output onto the communications bus.%t is easier for the supplier to design the instrument panel because hedoesn&t need to know any details of how the speed signal is generated,

or where it&s coming from. %nstead, the instrument panel simply monitorsthe communications bus and updates the gauges when it receives new

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data.!hese types of communications standards make it very uncomplicatedfor carmakers to outsource the design and manufacture of components!he carmaker doesn&t have to worry about the details of how eachgauge or light is driven, and the supplier who makes the instrumentpanel doesn&t have to worry about where the signals are coming from.

Smart SensorsClusters are now being used on a smaller scale for sensors. 3orinstance, a traditional pressure sensor contains a device that outputs avarying voltage depending on the pressure applied to the device./sually, the voltage output is not linear, depends on the temperatureand is a low"level voltage that re2uires amplification.Some sensor manufacturers are providing a smart sensor that is

integrated with all the electronics, along with a microprocessor thatenables it to read the voltage, calibrates it using temperature"compensation curves and digitally outputs the pressure onto thecommunications bus.!his saves the carmaker from having to know all the dirty details of thesensor, and saves processing power in the module, which otherwisewould have to do these calculations. %t makes the supplier, who is mostup on the details of the sensor anyway, responsible for providing anaccurate reading.

Another advantage of the smart sensor is that the digital signal traveling

over the communications bus is less susceptible to electrical noise. Ananalog voltage traveling through a wire can pick up e*tra voltage whenit passes certain electrical components, or even from overhead powerlines.Communication buses and microprocessors also help simplify the wiringthrough multiple$ing . ?et&s take a closer look at how they do this.

oors with lots of switches are %ecoming more and more common.

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Simplified &iring7ultiple*ing is a techni2ue that can simplify the wiring in a car. %n oldercars, the wires from each switch run to the device they power. (ithmore and more devices at the driver&s command each year,

multiple$ing is necessary to keep the wiring from getting out of control.%n a multiple*ed system, a module containing at least onemicroprocessor consolidates inputs and outputs for an area of the car.3or instance, cars that have lots of controls on the door may have adriver&s"door module. Some cars have power"window, power"mirror,power"lock and even power"seat controls on the door. %t would beimpractical to run the thick bundle of wires that would come from asystem like this out of the door. %nstead, the driver&s"door modulemonitors all of the switches.ere&s how it works %f the driver presses his window switch, the door

module closes a relay that provides power to the window motor. %f thedriver presses the switch to ad ust the passenger"side mirror, thedriver&s door module sends a packet of data onto the communicationbus of the car. !his packet tells a different module to energi1e one ofthe power"mirror motors. %n this way, most of the signals that leave thedriver&s door are consolidated onto the two wires that form thecommunication bus.!he development of new safety systems has also increased the numberof microprocessors in cars. (e&ll talk about this in the ne*t section.

Safet"' Comfort and Convenience;ver the last decade, we&ve seen safety systems such as A'S and airbags become common on cars. ;ther safety features such as traction"control and stability"control systems are starting to become common aswell. Each of these systems adds a new module to the car, and thismodule contains multiple microprocessors. %n the future, there will bemore and more of these modules all over the car as new safety systemsare added.Each of these safety systems re2uires more processing power, and isusually packaged in its own electronics module. 'ut it doesn&t end there.%n coming years, we&ll have all kinds of new convenience features in ourcars, and each of these re2uires more electronics modules containingmultiple microprocessors.%t seems that there is no limit to how much technology carmakers aregoing to pack into our cars. !he addition of all these electronic featuresis one of the factors driving carmakers to increase the system voltageon cars from the current 86": system to a 6 ": system. !his will helpprovide the e*tra power these modules re2uire.3or more information on car computers and related topics, check outthe links on the ne*t page.

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(ots #ore )nformationRelated HowStuff&or*s Articles• ow Anti"?ock 'rakes (ork• ow Auto Airbags (ork• ow 9ower (indows (ork• ow 9ower <oor ?ocks (ork• ow 7icroprocessors (ork• ow 3lying Cars (ill (ork• Stability Control • 9roper Child Safety 9recautions %n Automobiles

#ore +reat (in*s• Car Computer Components " illustrated• (hat&s All !his About a Computer in 7y Car@• :olvo S 0 7ultiple* System <escription• ow Engine Control Computers ;perate• %ntel %ntroduction to %n":ehicle $etworking

%ntel %mplementing the B8 50 9rotocol