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ECET-402                                    Week 4 Lab

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Emergency Lighting System




The circuit shown below in Figure 4 can be used to simulate an Emergency Lighting System, that is, a scheme to illuminate some lights from a Backup Power source when either the Primary Power source or a strategic Lamp fails. 





Figure 3. An Emergency Lighting System.


                       The Main lamp is connected to the Primary Power through the relay coil. The                             Emergency lamp will be connected to the Backup Power if either the Primary                              Power or the Main lamp fails. The circuit is shown in the normal mode of                                            operation, with the Main lamp connected to the Primary Power.




In this scheme, the relay coil and Main lamp are connected in series to the Primary Power, a 12 Volt battery. As long as the Primary Power remains on and the lamp is good, the relay will be energized, closing the normally open (NO) contact, and the Emergency lamp will not be connected to the Backup Power. If the relay coil becomes de-energized due to either the loss of the PRIMARY POWER or the failure of the Main lamp (an open circuit), the relay contact will return to the normally closed (NC) position, connecting the Emergency lamp to the Backup Power, restoring lighting. In a "real-life" situation, the relay coil and Main lamp would be connected to 120 Volts AC while the Emergency lamp would be powered by a 12 Volt battery. In addition, there would be provisions to keep the 12 Volt battery fully charged while the Primary Power is on.








Backup Power System




The circuit shown in Figure 5 shows a method of providing Backup Power to a load (the lamp in this case) when the Primary Power source fails. 





Figure 5. A Backup Power system.


The lamp X1 is normally energized by the 12 Volt Primary Power source. The circuit is shown in the Backup mode due to the loss of Primary Power.




The Primary Power, a 12 Volt battery, is connected across the relay coil. As long as the relay is energized, the lamp will be connected to the Primary Power via the NO relay contact. When the Primary Power is removed, or fails, as shown, the lamp will be connected to the 9 Volt Backup Battery via the NC relay contact.


Simulate the circuit in Multisim and check its operation


Provide a MultiSim simulation of the circuit with SW J1 open and closed ( 2 pictures)

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