A power supply is hardware (and sometimes may include software or drivers) that provides electric energy to an electric load. It may obtain its power from a transmission system, for instance power supplies that convert AC currents to DC, from storage devices such as cells or batteries, or from systems like alternators or generators. Power supplies can be integrated with their loads, or consist of stand-alone appliances. A low-voltage supply, such as a 12v DC power supply, is usually integrated with its load in domestic electronic appliances or computers.
The importance of these power supplies is that when used for building circuits, they can reduce the 120 volts at an outlet to 12 volts which is more manageable. Most small circuits need a maximum of 12 volts in order to operate. A current of 120 volts would almost certainly cause them to burn up very quickly.
There are a large variety of situations where you might need a 12v DC power supply, and a wide variety of products are available. One of the most common is a battery backup, such as the CRL Locknetics 500 Series Low Voltage Regulated Power Supply, or the Belkin Battery Backup UPS Unit. These are used for charging Blackberrys, cellphones, MP3 players or iPods, as well as larger items of equipment. A 12v Power Cord such as the Apevia ATX-AS500W 12V Power Supply, makes it possible to charge a cellphone or iPod from a car cigarette lighter. You can also find a 12v DC Power Adapter, such as Netgear PWR-10027-01 AC/DC Power Adapter, that enables you to use high power 12v DC items from 110v AC sources. Another product is the 12v ATX Power Supply, such as the Apevia ATX-CW420W Power Supply, normally used in desktop computers.
A supply will be used for different devices according to how many amps it provides. For instance a 3 amp one is used for such appliances as cellphones, LCD monitors, or portable DVD players for the car. A 12v DC 1A 1 amp is used in MP3 players and consoles, and enables you to charge other batteries from your car, or charge up your appliances while away from home. It is important to read the instructions for your electrical items before buying a power supply, to make sure you use the correct type of current, otherwise you risk damaging the device. The low and medium power ones that is, from less than 12 watts or 1 amp through to 10 amps are reasonably easy to obtain, but above 10 amps they become quite expensive and much harder to obtain.
One way of solving this problem is to obtain a computer PSU to convert. These are much cheaper and in fact, it is sometimes possible to get hold of a supply of free computer PSUs from scrap computers. Modifying a computer PSU is not difficult, and a big advantage is their powerful cooling fans, which greatly increase their efficiency.
Anybody who is keen on do-it-yourself projects will need a 12v DC power supply, since most renewable energy systems they use are connected to 12v battery banks. They are needed in all aspects of life and it is clear that it would be difficult to conduct our lives without them.
