Variable power supply and charger with emergency light

● A simple circuit of variable power supply and charger is described here. It is useful when the mains power supply is available or when there is no power supply.

● This circuit can be used for testing electronic projects at your work bench.

● It can be used to charge your mobile battery.

● It can be used as an emergency light.

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Fig. 1: Prototype Of Variable Power Supply Circuit On Breadboard

In this circuit you can take outputs by flipping the different switches (S3, S4 and S5) according to your requirement. Engage switch S3 if you want a variable power supply as output. For variable power supply, we have used variable voltage regulator LM317whichis a 3 terminal adjustable positive voltage regulator. It will provide an output voltage in the range of 1.2V to 37V. For obtaining different voltages, adjust the variable resistor to see the output on the multimeter and set the required voltage. Range of power supply varies from 1.5V-12V.

With the help of this circuit, you can charge your Li-ion battery by flipping the switch S5, which are mostly used in your mobile phones.. Here zener diode provides constant voltage of 3.3V to charge Li-ion battery. Resistor R13 is used to limit the charging current.

For using emergency light flip switch S4. If you want to increase the intensity of light you can use reflectors.

This circuit can be powered with AC supply or with the help of battery for that we have provided two switch S1 and S2. Flip switch S1 for AC supply and S2 for battery. You can also use a solar panel in place of AC supply and store charge in rechargeable batteries. It will not only save your electricity bill but also help you in case of power failure.