Choosing a Power Supply for your RepRap

The power supply (PSU or Power Supply Unit) is a most essential component of any RepRap, yet the information over which power supply to choose/buy is very much scattered around the web, in YouTube videos, and in various forums, blogs and wikis. Also there is little information concerning safety issues and these should be the absolute priority when dealing with PSUs.

The purpose of this page is to help the RepRap builder choose a proper PSU for her/his project, and deal with any safety issues that may arise related to the PSU.

Switch-mode power supplies

Nowadays (2014) practically all power supplies within the power range required by RepRap printers are switch-mode power supplies (as opposed to linear power supplies, which are considered outdated). Switch-mode power supplies have relatively complex circuits that convert mains AC electricity to the DC voltages required by RepRap steppers and electronic circuits. The design and manufacturing of switch-mode power supplies is way beyond the reach of any hobbyist, leaving a single alternative for RepRap builders: to buy a commercial switch-mode PSU.

LED strip or ATX PSUs

Economies of scale play an important part in determining the price and availability of a switch-mode power supply. So when looking to buy a PSU for her/his RepRap, the RepRap builder has in reality just two choices: what can be called the LED strip PSU, or a modern ATX PSU.

LED strip PSUs are switch-mode PSUs designed to supply a fixed DC 12V or 24V rail with relatively high current capabilities (anywhere from 15A to 30A or more) to a strip of dozens or hundreds of LEDs, each consuming a small percentage of the total current. In the last couple of years, they have become relatively inexpensive and are now widely available. They are even currently included with many commercial RepRap kits. However, one must keep in mind their original design requirements: powering LEDS is not a particularly difficult task, as these are relatively forgiving electronic devices. Also, since LED strip PSU manufacturers are not forced to comply with any specific requirements apart from the basic ones that will get them through the usual test laboratories certifications, there is a big variation in quality and price, and it is practically impossible for the hobbyist to choose one LED strip PSU over another on any rational basis.

ATX PSUs on the other hand have been around for decades and have evolved over time, adapting to the ever-changing PC market. There is an "official" ATX specification that is revised every few years and that is available as a PDF document for free download. ATX PSU manufacturers can claim that their products conform to these specifications (or not) as this is seen as an attractive feature for consumers. The latest ATX specifications include not only precise technical specifications, but also a number of safety requirements as well as some ergonomic requirements. ATX PSUs get regularly opened and dissected in specialized hobbyist websites, and some brands have established themselves as having reliable products with a good price/performance ratio.