How to build a 12v 5a power supply

Written by william kinsey
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How to build a 12v 5a power supply
Power Supply (power supply image by pmphoto from

Any good hobbyist who likes to build electronic circuits knows the advantages of having a good power supply. The supply must be strong enough to power the majority of the projects proposed and still stay within a reasonable budget. Because of the difficulty of choosing the right power supply from a catalogue, many hobbyists choose to build their own. By building your own, it can be customised to your specific needs and specifications.

Skill level:

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Things you need

  • Wire stripper
  • Wire cutter
  • 120 volt to 12 volt transformer capable of producing at least 5 amps of current
  • 10 amp bridge rectifier

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  1. 1

    Cut the receptacle plug off of an extension cord. Strip 1/2 inch of insulation off of the two wires. Connect one of these two wires to one of the primary terminals of the transformer. Connect the other wire to one side of a 120-volt AC switch. Connect the other side of the AC switch to the remaining primary terminal. The polarity of the input power does not matter since this will be a DC power supply. The transformer will step down the 120 volts AC available from a receptacle to approximately 12 volts AC. The transformer has to be rated to produce 12 volts and 5 amps minimum.

  2. 2

    Connect one of the secondary terminals, of the transformer, to one of the input terminals of the bridge rectifier. Connect the other secondary terminal to the second input terminal. The bridge rectifier will convert the 12 volts AC to 12 volts DC. The bridge rectifier needs to be rated to handle at least 5 amps.

  3. 3

    Secure each component to a housing. This can be an ordinary wood block or an electronic housing from Radio Shack or other electronics company. turn on the power supply. Using a voltage meter, check the voltage reading at the output side of the bridge rectifier. The voltage will probably vary between 13 volts and 11 volts depending on the voltage from the receptacle. To keep the voltage more normalised to 12 volts will require a voltage regulator.

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