RELIABLE EMERGENCY LIGHTING
The reliable emergency lighting circuit is an electronics project designed to give an emergency light when the power from main power supply fail or there is an electric cutoff
This is done by a backup battery source which is charged by a main power supply, when the power fail the battery will discharge through the lamps
From the circuit diagram of the reliable emergency lighting circuit ,several components will be used to accomplish the project ,these components are of different properties depending on their intended operation on the circuit
The table below shows some important components with their specifications that will be used in construction of circuit.
The input voltage of about 220V ac is passed to the step-down transformer of 20:1 ratio.
From
NP/NS=VP/VS
10/1=220/VS
VS=22V AC
But
Vdc=0.636Vm
Vm= √2Vs
Where, Vs=22v
Vm= √2×22v
Vm=31.11
Vdc= 0.636x31.11
Vdc=19.79v dc
Where
From the datasheet the current rating of the LED is 10mA and the voltage is 2V hence from the series connection of the LED and the resistor
Vs=Vd + Vr
19.79=2+Vr
Vr=19.79-2
Vr=17.79
Therefore
Vr=IR
R=Vr/I
R=19.79/10mA
1.979kΩ
The resistor used is approximately 2kΩ
The transistor help to energize the relay when it act as short circuit causing the battery to be charged by the main power supply.
From
V out =Vz-V be
V out =15.65-0.65
V out =15
This is the amount of constant voltage that will be allowed to pass out of Zener diode
Rz=(Vin-Vz)/Iz
Rz=R3=(15.65-0.65)/15.5mA
Rz=R3=0.967kΩ
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