Page 335 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton
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                                                                    Electrical systems                             317


                                   RF Receiver/
                                    Transmitter

                        Supply






                                    Control Unit
                   Door Switch(s)                   M       M       M      M




                                                           Lock Motors




                                   Other Systems
                                    (Alarm etc.)


              Figure 3.121      Circuit to operate door locks



            code and sends it in an electrical form to the main control unit. If the received
            code is correct, the relays are triggered and the door locks are either locked or
            unlocked. If an incorrect code is received on three consecutive occasions when                     Key fact
            attempting to unlock the doors, then some systems will switch off until the door           Trillions of different code
            is opened by the key. This technique prevents a scanning-type transmitter unit   combinations are used in modern
            from being used to open the doors.                                           locking systems.


                3.4.5.5  Windows

              The basic form of electric window operation is similar to many of the systems
            discussed so far in this module; that is, a motor reversing system either using
            relays or directly by a switch. More sophisticated systems are now popular for
            reasons of safety as well as improved comfort. The following features are now
            available from many manufacturers:
                      one touch up or down
            ●
                    inch up or down
            ●
                    lazy lock
            ●
                    back off or bounce back.
            ●
                  The complete system consists of an electronic control unit containing the
            window motor relays, switch packs and a link to the door lock and sunroof
            circuits. This is represented in the form of a block diagram in  Fig. 3.122   .
              When a window is operated in ‘one-touch’ mode, the window is driven in the
            chosen direction until the switch position is reversed, the motor stalls or the
            ECU receives a signal from the door lock circuit. The problem with one-touch
            operation is that if a child, for example, should become trapped in the window                     Key fact
            there is a serious risk of injury. To prevent this, a bounce-back feature is used.           A bounce-back feature is used to
            An extra commutator is fi tted to the motor armature. This produces a signal, via   prevent people and things being
            two brushes, proportional to the motor speed. Hall sensors are used on some   trapped in windows.
            systems. If the rate of change of speed of the motor is detected as being below a
            certain threshold, the ECU reverses the motor until the window is fully open.
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