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A Very Simple Power Failure Light
A Very
Simple Power Failure Light
|
Introduction |
This is a very basic power failure lighting
circuit based around a relay.
This simple circuit has many uses, from
lighting up rooms and walkways in the case
of a power failure, to monitoring and
security uses.
There are many
different power failure circuits out there
based on 555 timers or transistors but they
all have different problems including
limited input voltage, price and complexity,
and poor backup power. This unit has been
designed to work with mains power all the
way down to 5 volts, and power 3 LEDs to
provide light for a hallway or a child's
room in the event of power failure. The PCB
includes many simple add-ons and
modifications too.
Specs
Input Voltage Max: 240 Volts AC
Input Voltage Min: 5 Volts DC
Approximant Power Consumption: 450 mW
|
Schematic |
|
Explanation |
This circuit is connected
to ac power through
J1
then rectified to dc through
D1-D4.
D5 is a 12 volt zener diode being used along
with the resistor
R1
and the coil resistance of relay
RL1
to regulate the input voltage to 12 volts and
C1 is
used to help smooth this power.
Alternatively a dc voltage of 5 volts or more can be connected directly to J2 and J3, positive to J2 and negative to J3; in this setup the circuit would not need J1, D1-D5, and R1.
The relay RL1 is a SPDT 5vDc relay and when power is applied to it, it opens the circuit with the LEDs so they are off as long as power is on if the power goes off, the relay closes the circuit and the battery BAT1 powers the LEDs D6, D7, and D8. In this circuit BAT1 is a 9 volt battery that powers the 3 LEDs through R3; however BAT1 can be many different batteries depending on your needs. J4 is also available in parallel with the LEDs to connect a buzzer or etc.
You can also put a switch on one of the
wires for BAT1 so you can turn it off so that you don't drain it when the
circuit is not being used.
|
Parts List |
|
1 |
R1 |
1.2k Ohm |
|
1 |
R3 |
120 Ohm |
|
1 |
C1 |
470uF |
|
4 |
D1-D4 |
1N4004 |
|
1 |
D5 |
1N4742A |
|
3 |
D6-D8 |
White
LED |
|
1 |
RL1* |
5 Volt
SPDT Relay T7CV5D-05 |
|
1 |
BAT1 |
9V |
|
1 |
- |
9V
Battery Connector |
*There are many different relays that can be
used, some that even use next to no power.
|
PCB |
|
Download |
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