How to Convert 120 AC to 12 Voltby Abraham Robinson
Different electronic devices are built to run at different voltages and types of current. In the United States, the the voltage of typical wall outlets is 120 volts, also called mains voltage, and it provides an alternating current, which means that the flow of electricity regularly switches direction. Some power sources, however, most notably car batteries, run on a 12-volt direct current. There are times when you may want to run a device built for a mains voltage from a 12-volt power source or the other way around. In order to do this, you need either a power converter or a power inverter.
Setting up a power inverter.
Plug the cord from the power inverter into your car cigarette lighter. Because the most common source of 12-volt DC is a car battery, most power inverters are set up to draw power from a standard car cigarette lighter. If you are using a different type of low-voltage power source, follow the directions that came with your inverter unit. In most cases, you will need to connect cables to the positive and negative leads of your power source.
Plug your 120-volt AC appliance into the 120-volt outlet plug on the power inverter. Most power inverters have a plug shaped just like a normal wall outlet.
Turn on your device and use it normally. Many power inverters have an indicator light that shows that they are working properly. Check that this light is on. Keep in mind that you may need to switch the device on before it begins to provide power.
Setting up a power convertor.
Plug the normal-looking electrical cord from your power converter into a 120-volt wall outlet.
Connect the cables from your device to the positive and negative leads on the front of your power converter. There should be two places on the power converter to connect the cables--one marked as positive and one marked as negative, and usually colored black and red. Make sure that you connect the positive lead on the converter to the positive cable from your device. Getting the positive and negative cables mixed up could cause your device to not work or even damage it.
Switch your power converter on. Electricity should now be flowing, and your device should work normally.