Simple Emergency LED Light Circuit

Simple Emergency LED Light Circuit

This emergency LED light is simple, inexpensive and easy to build. The circuit to the battery and when the main source is not available, such as brownouts, white LEDs turns on automatically.

Initially, the output voltage from 220V to 12V converter is fed to the input of LM317 regulator. Then, this voltage is regulated to 7.37V with 240 ohms and the combination of the resistance of 1.2K (see LM317 Calculator).

At this time, the battery is in charging mode and the transistor Q1 is off. LED serves two purposes, one is mainly to give us an idea of ​​the battery is charging and the other is to ensure that Q1 is off.

During voltage drops, the transistor Q1 is on and supplies the current to 16 white LED of about 20 mA each, so a fully charged battery (6V/4.5Ah) may last up to 14 hours.

The charger has a built in over current control, but still protects the battery from overcharging and charging voltage is at 7.4V only.

Continue Reading of Simple Emergency LED Light Circuit...

Automatic Night Light Circuit using NE555

Automatic night light cheap and simple with few transistors and the NE555 timer is shown here. The circuit automatically turns on AC lamp after dark and the light turns off automatically after a preset time.

The operation of this circuit very simple night light. A LDR is used as the sensor here. At the time of day of the LDR resistance will be low as the voltage drop across it, the transistor Q1 will be on how to carry out. When darkness falls the resistance of LDR increases, so does the voltage across it. This causes the transistor Q1 OFF. Base of Q2 is connected to the emitter of Q1 and Q2 which is biased in that turn, the powers of IC1. NE555 is wired as monostable multivibrator which is activated automatically when the power is.

This automatic release is achieved with the help of the capacitor C2. The output of IC1 remains high for a time determined by resistor R5 and capacitor C4. When the output of IC1 goes high transistor Q3 is turned on which activates triac T1 and lit the lamp. A 9V battery is included in the circuit to power the timing circuit during power failures. Resistor R1, diode D1, capacitor C1 and Zener D3 is the feed section of the circuit. R7 and R8 are current limiting resistors.

Continue Reading of Automatic Night Light Circuit using NE555...