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tutorial-power-supplies is a tutorial about how to choose and what consider when using a power supply, building a simple power supply out of batteries, common power supplies, and commercially available power supplies.

This tutorial was written by Aarón Montoya-Moraga. If you want to check out more tutorials, visit

It is also available in Spanish. It is written in Markdown and hosted in GitHub.


There are a lot of power supplies to choose from.

Electrical power supplies transmit power, which is the product between voltage and current. They provide a fixed voltage, and they transmit as much current as needed by the device to comply with the power requirements.

Power supplies usually connect to mains voltage


  • Input voltage
  • Output voltage
  • AC or DC
  • Current rating
  • Polarity
  • Physical connector

Input Voltage

Power supplies need an input. They usually connect to a mains outlet. In USA, mains outlets are 110 XX volts AC. In Japan, they are 120 XX volts AC. In most of the world it is 220 or 230 volts AC. The corresponding XX do a table instead of plain text.

Output voltage

AC or DC

Current rating


In the case of DC, you need to know if the connection is center-positive, or center-negative. The barrel that transmits the output of the power supply consists of an outer conductor and an inner conductor.

A center-positive power supply outputs the voltage on the inside and ground on the outside.

A center-negative power supply outputs the voltage on the inside and ground on the outside.

Physical connector

There are several diameters of barrels. XX Check the 1Spot and research about propietary ones if any. Remember the PROCO Rat and EHX Big Muff ones.


Voltage ranges, overheating, common mistakes


Power supplies out of batteries

Voltage regulators

Voltage regulators are integrated chips that consist of three terminals:

There are several flavors

LM7812l LM7805

Some standards

Guitar effect pedals 9Vdc center negative

Synthesizers 9Vdc center positive

Propietary connectors, Apple Magsafe and Magsafe 2, Apple Lightning.

Power through USB, USB-C Arduinos, cellphones

Commercial alternatives and examples

Truetone 1Spot power supply


Laboratory power supplies


This tutorial was made possible by the author's research residency at NYU ITP during the 2017/2018 academic year.

Special thanks

  • Bernardita Moraga, for letting me fill her house with power supplies.
  • Víctor Montoya, for teaching me electricity, physics, and soldering.
  • Ángel Abusleme, for being an excellent mentor.
  • Guillermo Montecinos, for all the collaborations we have had over the years.
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