Clap Switch Circuit

The transformer is 220V to 15V -0V-15V transformer of a minimum of 10VA. You can replace the 1N4001 diodes of any types with similar ratings.The relay is 12V with 5A output current capacity or higher. You can replace also the transistor of any general purpose type.

Note: This clap activated relay is connected to main supply (220VAC). Do not try to touch the main supply to avoid electrocution or do not try to construct if you do not have any idea in electronics.

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Led emergency light using cellphone battery and charger

Emergency lighting system uses LED and powered by a 3.6V cellphone battery or any battery of the same voltage. The battery is charge by a cellphone charger with a current of 350mA. During the
charging process, transistor Q1 is off so are the LEDs. When the power is cutoff (brownout), transistor is energized an delivers 25mA current to the four LED. The emergency light consumes about 0.5W and a fully charge battery can last up to 5hours.

Parts List
D2, D3, D4, D5- preferably white LEDs
Q1- 9012 or any general purpose pnp transistor
cellphone battery or similar
Battery charger
1000uF /10V capacitor
4.7k and 220 ohms 0.25W resistor
5 ohms 1W resistor

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Simple LED Emergency Light Circuit

Emergency light project is simple, cheap and easy to build. The circuit do the charging of the battery and when the main source is not available such as in brownouts, the white LEDs
automatically turn on.

Initially, the voltage output from 220V to 12V converter is fed to the input of LM317 regulator. Then this voltage is regulated down to 7.37V using 240 ohms and 1.2K resistor combination (see LM317 Calculator). At this instant, the battery is in charging mode and the transistor Q1 is off. Indicator LED serves two purpose, one primarily is to give us idea
that the battery is charging and another is to ensure that the Q1 is off. During brownouts, the transistor Q1 is on and delivers current to 16 white LED of about 20mA each, thus a fully charged battery (6V/4.5Ah) can last up to 14 hours.

The charger has no built in over-current control but still it protects the battery from overcharging since the charging voltage is set only to 7.4V.

Project materials:
1pc - transformer - 220V to 12V-0-12V , center tap 12VA
16pc - 120 ohms resistor 1/4 W
16pc - white LED min 3V@30mA
1pc - red LED
1pc - 1000uF/25V electrolytic capacitor
3pc - 1N4001 diode
1pc - LM317 regulator
1pc - 1.5K resistor 1/4W
1pc - 240 ohms resistor 1/4W
1pc - 1.2k resistor 1/4W
1pc - 9012 pnp transistor or any of much higher capacity
1pc - 6V 4.5ah battery

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6V to 12V dc-dc boost converter by 555 timer

This 6V to 12V dc-dc boost converter can drive a load in 12V about 3A current.The 555 timer IC is operated in astable mode, generates about 29Khz frequency of about 54% duty cycle drives the input of TIP41C transistor.1000uF capacitor smoothens the output voltage of the dc-dc converter.LED and 1.5Kohm resistor serves as indicator and load for output stability when no load is connected.You can add a 12V zener diode (1N5242B)across output to ground for further output stability.

The 39ohm resistor at the base of transistor is rated 1W, the rest 1/4W or more.Inductor can be made out of #22AWG wire wound around on an old transistor radio ferrite core.Number of turns more than 30T, but not critical.Change the values and experiment more using this circuit.

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12V to 5V DC converter using 7805 regulator IC

This simple converter project uses 7805 IC to convert 12V dc from a battery to 5V DC. This converter also can be made even only one component, the 7805 regulator. Converter can produce a maximum current of 1.5A (with heatsink) at 5V from an input of 8V to 15V. The capacitors are optional and can be omitted.
This is suitable for powering devices that uses 5V DC such as chargers,USB devices and others

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