How you calculate the 220V AC to 12V DC?

Answer 1

First you need a step down transformer. A step down transformer has less turns of copper in secondary then in primary. You can calculate with this formula
# of primary turns/Voltage of Primary= # of secondary turns/Voltage of secondary
When you know 3 factors, you can easily find out the forth one by easy mathematical calculation
From a step down transformer the 12 V AC output, needs to be converted into 12 V DC by a simple reverse bias or diode
A diode does a HALF-WAY RECTIFICATION
which means it allows one way of current, cut downs the reverse that is AC Current in which change of polarity takes place
or
a diode rectifies AC to DC or unidirectional current

Answer 2

There are a variety of ways to do it but it is vital to note that a transformerless power supply is not isolated from the mains supply. Anything that is attached to it will also not be isolated from the mains supply.

The simplest method is to use a half wave rectifier followed by a resistive network to drop the voltage to a suitable level. This is a solution where minimal current is required as the power dissipated by the resistor network will be about 20 times the power used by the low voltage load. Efficiency with this method will be around 5%.

More complex solutions use switching circuits such as buck converters. These can be much more efficient (95% in some cases) and are able to provide good voltage stability.

It is vital that any design that connects directly to any mains supply is supplied by a qualified and experienced designer and is used only for applications where users will not be exposed to any part of the circuit. Getting it wrong can have fatal consequences.

Answer 3

You will need to use a step down transformer with a full wave rectifier. The rectifier is a series of diodes installed in such a manner so that when alternating current is introduced through it's pathway it becomes a direct current one direction. The diodes are basically check valves that allow flow in one direction, which prevents the return cycle pathway of the alternating electrons to return. Therefore it has only one direction in which to achieve it's ultimate goal, to reach ground. The item that has developed most recently in this field is the VFD's or variable frequency drive. Coming in multitude of configurations from phase conversion to motor drives and can be purchased through most home improvement stores. Smaller versions should be available through most electronic suppliers {Zack-its, Radio Shack, etc..} but are limited in size.

Answer 4

You can use a transformer to step down the voltage from 220V AC to a lower voltage, then rectify it using a bridge rectifier to convert it to DC. Finally, you can use a voltage regulator circuit to stabilize the output at 12V DC.

Answer 5

You need a power inverter or a mechanical motor-generator.

Answer 6

Use Inverter Use Inverter