Automatic emergency light LED circuit

The automatic power failure emergency light charges the battery when the power is ON and automatically lights ON the LED when the power goes out.

emergency light automatic power failure

The circuit consists of a battery charging section, with a regulated and limited current DC supply of 6V and relay controlled LED lights.

The relay energised when the supply has a live line. So the common pole of the relay contacts to the normally open terminal. Thus, the battery connects to the input DC supply and charges.

When power fails, the relay changes to Normally closed position and the battery switches to the LED light. Here we are using a five parallel set of two 3V LEDs in series. So, without any resistors, a 6V battery can connect directly to LEDs.

The switch S1 can be used to select whether the light to be always ON automatically or to ON/OFF manually. For a permanent automatic operation, the switch can be closed always or shorted instead.

Emergency light – Components required

LM317 – Voltage Regulator

Resistor – R1, R4 – 1k, R2 – 3.9k, R3- 2ohms

Capacitor – C1 – 2200uf

Diode – D1-D5 -1N4007, D6-D15 – White LED 3V

Transistor – Q1- BC547

Transformer – T1- 230V/6V,1A

Relay – SPDT relay 6V

Switch – S1 – SPST

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6 Responses

  1. Harish says:

    Circuit not woking on battery

  2. Sandeep says:

    how can I use LDR for the above circuit?

  3. olatunji says:

    with the diagram. will the lamp on when the mains is on. and also there’s no charging indicator for rhe battery

    • admin says:

      No, when the main is on the relay is energized and the battery terminal will be connected to relay NO, which is the Input supply.
      Yes, it has no charging indicator, but you can simply add it by connecting an LED (with a resistor) at pin 2 of LM317.

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