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This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen. When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored.

Emergency Light and Alarm Circuit Diagram

Parts List:

R1 = 220K
R2 = 470R
R3 = 390R
R4 = 1.5K
R5 = 1R
R6 = 10K
R7 = 330K
R8 = 470R
R9 = 100R
D1 = 1N4007
D2 = 1N4007
D3 = 1N4007
D4 = 1N4007
D5 = 1N4007
D6 = Led
D7 = 1N4148
Q1 = BC547
Q2 = BC327
Q3 = BC547
Q4 = BC547
Q5 = BC327
C1 = 330nF-400V
C2 = 10uF-63V
C3 = 100nF-63V
C4 = 10nF-63V
LP1 = 2.5V-300mA Torch Lamp Bulb
PL1 = Male Mains Plug
SW1 = SPST Switches
SW2 = SPST Switches
SW3 = SPDT Switches
SPKR = 8 Ohms Loudspeaker
B1 = 2.5V Battery (two AA NI-CD rechargeable cells wired in series)

Mains voltage is reduced to about 12V DC at C2s terminals, by means of the reactance of C1 and the diode bridge (D1-D4). This avoids the use of a mains transformer. Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging.

Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair. If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker.

If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2. If SW1 is closed, restoration of the mains supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.

Note:

Close SW2 after the circuit is plugged.

Warning!

The circuit is connected to 230Vac mains, then some parts in the circuit board are subjected to lethal potential!. Avoid touching the circuit when plugged and enclose it in a plastic box.

Here is an emergency lighting based on white LEDs offer the following advantages:

1. It is very bright thanks to the use of white LEDs.

2. The light turns on automatically when the mains fails and shuts down when power resumes.

3. It has its own office. When the battery is fully charged, the charging stops.

The circuit consists of two parts: the charger from the socket and the power LED part driver.The Charger is built around the 3-terminal adjustable regulator (IC1) LM317, while the LED driver is built on part of the transistor BD140 (T2). In the power charger power transformer in the AC input is a step down to give a 9V 500mA bridge rectifier consisting of diodes (IN4007x4). Filter capacitor (25v/1000uf) to eliminate the ripples. Unregulated DC power is fed to IC1 pin 3 and provides a charging current through the diode IN4007 (D5) and limiting resistance (16ohm) R16. By providing pre-k 2.2 (VR1), the output voltage can be adjusted to provide the required charging current. When the battery may require a 6.8V, and the barrier makes the charging current regulator (IC1) to find a path through the transistor BC547 (T1) to ground and stops charging. LED driver section is used a total of twelve 10 mm white LEDs.

Circuit diagram :

Automatic Low Cost Emergency Light LM317  Circuit diagram

All LEDs are connected in parallel with the resistance of 100 ohms in series with each other. junction common anode for all twelve LED is connected to the collector of PNP transistor T2 and the emission level of the transistor T2 is directly related to the positive terminal of 6V battery. Unregulated DC voltage produced by the cathode junction of Bridge (diodes), is fed to create a transistor T2 through a resistor of 1k. When the voltage is available, the fund is still high transistor T2 and T2 does not happen. The lights are off. On the other hand, if the power does not, the transistor T2 will be a small fund and it does. This causes all the LEDs (LED1 through LED12) is lit. Network, as it is available, download and keep the lights off the battery as an indicator of transistor T2 is cut-off. During the blackout, the workload is steady and makes the battery will light up.

Assemble the circuit on a general purpose PCB and enclose in a cabinet with enough space for the battery and switches. Mount the LED in the housing to illuminate the room. A hole in the box must be drilled to connect the 230V AC input to the transformer primary. I tested the circuit with twelve white 10 mm LEDs.You can use several diodes, provided that the total energy consumption does not exceed 1.5. Driver transistor T2 can provide up to 1.5 In accordance with a proper heat sink.

Source : freecircuit.net