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Power Supply


Reprap psu s360 12V 30A.jpg
Power source for a printer electronics and components.
Wikipedia Switching Power Supply


A power supply or PSU transforms a 110V to 220V standard Alternate Current found in a home to a Direct Current suitable for the electronics and components.

Most Reprap electronics use 12V ranging from 5A-30A. Boards like the RAMPS 1.4 and other designs allow to use 24V while boards like the Duet are designed to operate at 24V.

The motors plus single hotend take up to 5A or so, a heated bed typically takes 5A-15A. So for a standard setup with heated bed, look to about 18-30A total which is about 220-360W at 12V. For some setups you might be able to use less power.

One of the main factor on selecting a PSU will be the power/current of a heatbed. The following table shows the power requirements and limits for some common RepRap electronics:

Reprap icon note.pngMake sure to read the Choosing a Power Supply for your RepRap wiki page.
Element RAMPS 1.4 RAMPS 1.6 RAMPS 1.7 DUET
Heatbed 11A max
limit dictated by MOSFETs
18A max
120W-160W, 216W (@24V)
limit dictated by MOSFETs
Extruder Heater 2.5A/30-40W avg
(heater power shared with motors & other components to a max of 5A)
6A each
Stepper Motors ~48W (5 motors), 2A peak
dictated by driver
(shared with other components to a max of 5A)
(traditional NEMA 17 motor is rated at ~2.5A max)
~48W (5 motors), 2A peak
dictated by driver
(traditional NEMA 17 motor is rated at ~2.5A max)
Controller ~2W, 5A max
(200mA max, 12V for Arduino ATMega2560)
(shared with extruder heater, motors & other components to a max of 5A)
Fans ~3.8W (two fans), ~150mA
dictated by actual fans
~3.8W (two fans), ~150mA
dictated by actual fans

There are several different options of power supply that can be used and are commonly available.

OEM type PSU

Commonly know as "CCTV" or "LED strip" power supplies. They are 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, or cameras. Due to the development of LED lighting in the recent years these PSU have become relatively inexpensive and widely available.

The S-360 is a common form-factor used in 3D printers. A basic 360W/30A rating works fine with RAMPS 1.4 boards.

Reprap icon warn.pngThere are a lot of cheap options available in online stores. Be careful as many retailers misrepresent the actual ratings, or use components of lower quality and have poor Quality Assurance. Always read the reviews. MeanWell is a reputable brand.

When selecting an OEM PSU make sure it provides safe screw terminals that provide an adequate level of isolation to you cable connections, that it has a closed frame and a proper plug panel for the power cord, finally judge the overall safety of the PSU and your installation requirements.

They come in several versions, 12V or 24V and up to 460W. The input voltage is usually universal, switchable between 110V and 220V, or sometimes fixed 110V or 220V. Check that it is compatible with your mains voltage before purchasing.

To help with the installation of these type of PSU (and for added safety) you will find many models of covers that you can print.

Computer PSUs

Standard ATX PSUs

Reprap icon warn.pngATX PSUs do not supply 24V.

These provide 12V, 5V, 3.3V and 5V standby. The power rating of an ATX PSU is the combined max load supported by its 12V, 5V and 3.3V outputs.

ATX PSUs are widely available and are suitable to power common RAMPS 1.x electronics. Some RepRap controller electronics have connectors for direct connection to the PSU Molex connectors, for other electronics the connectors will need to be cut and connection to stripped wires made. Some electronics (e.g. RAMPS) can use the Power-On signal to wake up the PSU from standby.

ATX PSUs vary a lot in quality and usually need to be oversized, as many cannot provide the rated power for a typical RepRap usage. A typical ATX PSU can usually provide about half its rated power on the +12V rail, so it is best to use a power supply rated 400W or above, and check what current the +12V rail(s) is(are) rated for. Otherwise the PSU will struggle to maintain a stable 12V output.

RAMPS controllers only use the +12V (at up to 16A) and eventually +5V (at less than 500mA) for servos.

Good ATX PSUs have thermal overload protection and shut down safely on overload, but again, poor quality ones may not do so before overheating.

To use an ATX PSU with RepRap electronics you need to connect "PS_ON" to the corresponding pin. It is also possible to short it to the ground, this makes PSU start as soon as it is plugged, but it is not recommnded, this would not give you control over PSU. Also depending on the particular ATX PSU model used, a dummy load on the 5V rail is required to get good regulation of the 12V rail.

See here for more details:

Server PSU

There are also PSUs taken from servers which can be used. These usually provide 12V only, but a LOT of current (32A), and quite cheap.

They usually have a proprietary connector designed for rack mount systems, so need some custom wiring depending on the model.

Here are instructions for HP PS-3381-1C1 400W PSUs http://www.rcgroups.com/forums/showthread.php?t=358340

Power Brick

General purpose power bricks

These come in a variety of types up to around 240W, for normal use select a 12V 220W version. Also available are 24V versions. [[1]]

They often come with a barrel type or 4 pin connector. The 4 pin connector is sometimes called "mini-DIN" or "power DIN", but is not a standard DIN connector.

Also the pin assignments can vary, but for most boards you will need to cut the connector off or make an adaptor.

References: http://en.wikipedia.org/wiki/DC_connector#Snap_and_lock_DC_power_connectors

Laptop chargers

Here are instructions for converting a Dell laptop charger : http://lbmakersociety.org/2012/12/creating-hacking-a-reprap-power-supply-for-ramps/


There are several versions, choose the 203W version. Note that the power may be insufficient for some heated beds. The PSU will shutdown if an overload occurs.

These provide 12V, 5V and 5V standby and power on input.

The XBOX power connector can be cut off and connections made to stripped wire, or make an adaptor with an XBOX power socket (sold as spares on eBay etc).

How to use XBOX 360 PSU with Reprap : http://www.thingiverse.com/thing:13980

Controlling the PSU

In order to save power and prevent possible fire hazards you can control the PSU. ATX PSUs are controlled by PS_ON Pin, and the rest should be controlled with a relay. When using relay you would also need a seprate 5V logic PSU to be always on. Having a Realay or PS_ON pin connected enables most firmwares to utilize M80 and M81 commands.


You can find PSUs about everywhere you can find electronics parts.

See also