| REUK Shop | REUK Blog | Directory | About Us  |  | RSS Web Feed for Renewable Energy UK 

Buy a 12v Power Supply Unit



Buy A 12v Power Supply Unit

Find out more about 12V mains transformers and power supply units

electric circuit | storage | general
  Printer Friendly Version Print Article     

Across our many hundreds of articles we frequently present circuits, systems, and appliances which are powered by 12 Volts DC - primarily because the majority of all DIY renewable energy systems are connected to 12V battery banks. However, we receive so many questions from REUK.co.uk site visitors asking us where to purchase a suitable plug-in power supply (mains transformer / PSU) that we have put our recommendations together in this one article.

Low Power - Less than 1 Amp


5 Watt (400mA) 12 Volt DC power supply unit
For power outputs below 12 Watts (1 Amp) you are spoiled for choice. Most of these PSU's are built into a standard mains plug (as pictured above) in small, lightweight units. Some are supplied with a selection of common connectors (including the most common 2.1mm and 2.5mm types), but others come fitted with just one connector (typically 2.1mm).

Look out for regulated power supplies (much better for sensitive electronics), and efficiency of at least 60%.

Rapid Online
5W Switch Mode Plugtop PSU (400 mA, 60% efficient)
15W Switch Mode Plugtop PSU (1.2 mA, 75% efficient)

Medium Power - 1.5A to 10A

Once you get to above 1.2 to 1.5 Amps, power supplies become a bit harder to find and are more expensive. However, they also tend to be made of better quality components, and are more efficient.

120 Watt 12 Volt power supply unit

Rapid Online *
25W 12V DC Miniature Desktop Switch Mode PSU (2 Amp, 80% efficient)
65W 12V DC Miniature Desktop Switch Mode PSU (5 Amp, 80% efficient)
90W 12V DC Miniature Desktop Switch Mode PSU (7 Amp, 80% efficient)
120W 12V DC Miniature Desktop Switch Mode PSU (10 Amp, built-in cooling fan)

* The Rapid products listed above have a built-in IEC320-C8 mains power inlet. A separate figure-of-8 power lead with plug must be purchased, but these are only £2 at Rapid: click here to buy now.

High Power - more than 10 Amps

Above 10 Amps (120 Watts) it becomes very difficult to find a power supply that is not very expensive. One common solution is to use a computer power supply unit. These are available from a couple of hundred Watts up to 1kW, and can therefore reliably supply 20, 30, 40 Amps etc cost effectively and fairly efficiently.

Computer PSU - 370 Watt 30 Amp 12VDC output

Computer PSU's are usually fitted with at least three or four output 12V connectors, so you may need to cannibalise a suitable output cable to get your 12 VDC output without opening up the case of the PSU.

One key advantage of using computer PSU's in this way, is that they are fitted with strong and quiet cooling fans as they are designed to be used in offices. Typically they offer 70% efficiency, however green power supply units are available now which give over 90% efficiency.

eBay UK
There are usually 3,000+ computer PSU's and other PSU's for sale on eBay UK at any one time. Click here to search now for PSU with prices starting from below £5.

Rapid
370W Computer PSU (30 Amp, 80mm cooling fan, just 37dB noise level, under £15 inc VAT)

Modifying a Computer PSU

Computer PSU's typically output +5V (yellow cables) and +12V (red cables), and the ground cables are black. (Sometimes there is also a low current -5V (white cable), -12V (blue cable), and power good (orange cable) which you will not be using.) The cables are fitted to connectors ready for quick plug-in connection to the computer motherboard, CPU, hard drive, etc. Simply cut off the connector plugs, group the wires of each colour together - i.e. all the reds, all the yellows, all the blacks - and solder the ends together.

Joining the wires together which emerge from a computer PSU

The current rating for each output from the PSU should be printed on the PSU case, so simply add up the total +12V Amps to calculate the absolute maximum current which can be taken from the PSU at 12 Volts DC. Put a fuse between the soldered end of the bundled red wires and the device to be powered for safety. Ideally the fuse should be rated at 10-20% below the maximum stated PSU +12V current rating, and you should use no more than 60-70% of the available current.

Make sure that the cable you use between the PSU and the device to be powered has a current rating in excess of that required by the device to be powered.



Article Last Modified: 11:16, 28th Nov 2012

Comment on this Article

If you have any comments on this article, please email them to neil@reuk.co.uk.

Just been converting (messing around with) an ATX PSU for a +ve 12v supply. Not sure if you have got your colours mixed upon here.

On this [power supply], the +ve 12v are the yellow wires and the +ve 5v are the red wires. See here: power supply basics inc pinouts. Also, there is a green wire that has to be connected to ground(Black) to get the PSU running.

Dave, 2nd March 2011


Recommended Related Articles

People who read this article also enjoyed the following articles:

Permanent Magnet Generator
Build a wind or water power system with around a PM Generator
Article Last Modified: 16:43, 6th Apr 2010
wind | hydro

Ways to Save Electricity
Find out how you can save electricity in your home - help the environment and save money.
Article Last Modified: 16:43, 2nd Jan 2013
energy efficiency | general

Ametek PM Motors
Use an Ametek PM Motor as a DC Generator for Wind or Hydro Power
Article Last Modified: 09:14, 22nd Jul 2008
wind | hydro

Three Phase Basics
Get an understanding of three phase wiring in wind turbine alternators
Article Last Modified: 15:13, 19th Aug 2008
wind | electric circuit | websites

Interconnecting Batteries for Battery Bank
Find out how best to connect batteries together into a battery bank
Article Last Modified: 13:53, 23rd Feb 2007
storage

Micro Hydro Simplified Guide
A simple guide to small scale hydro power generation ideal for DIY
Article Last Modified: 09:00, 21st Aug 2007
hydro | education

How I Built A Wind Turbine
Read how a wind turbine was built for under US$150
Article Last Modified: 15:16, 19th Aug 2008
wind | education

Transformers for 12V LED Lighting
Choosing a suitable transformer for use with 12 Volt DC LED lighting
Article Last Modified: 09:40, 30th Jun 2008
lighting | shopping

Cheap Pyroelectric Infrared PIR Detector
Details of a very affordable and flexible PIR motion detector
Article Last Modified: 20:33, 16th Jan 2013
electronics | education | electric circuit

PVC Wind Turbine Blades
Learn how to make your own PVC wind turbine blades
Article Last Modified: 15:16, 19th Aug 2008
wind

© 2006-2013 REUK - All Rights Reserved
Page Last Updated on 19th May 2013 at 08:29:13pm

Recent
Blog Posts


1.Offer of the Day – 80W Monocrystalline Solar Panel £71.98

2.Project of the Day – Wind Turbine Dynamic Blade Pitch Controller

3.Morocco Starts Vast Solar Energy Project

4.Follow Up to RC Helicopter Lighting Controller

5.Low Voltage Disconnect – User Programmable Set Points in Binary

6.UK Home Energy Smart Meter Project Delayed

7.EU to Impose High Import Duties on Chinese Made Solar Panels

8.Project of the Day – Swimming Pool Solar Water Heating Controller with Max Temperature

9.Multiple Buttons/Switches on one ADC Input

10.Standalone Arduino on a Breadboard


Latest
Articles


New Simple Hen House Door Controller
Details of our new 2013 simple design for an automatic hen house door controller
electric circuit
11:45, 20th Apr 2013

Automatic Hen House Door Closer Opener
Find out how to put together a DIY automatic hen house door opener and closer
electric circuit
11:40, 20th Apr 2013

Butanol vs Ethanol Fuel of the Future
A brief introduction to Butanol/Biobutanol as an alternative to Ethanol
biomass
11:55, 19th Apr 2013

Cheap Pyroelectric Infrared PIR Detector
Details of a very affordable and flexible PIR motion detector
electronics
20:33, 16th Jan 2013

Heat Pump Tumble Dryer
Reduce power consumption with the latest heat pump tumble dryer technology
energy efficiency
20:16, 3rd Jan 2013

LED Spotlights
Find out about Energy Efficient LED spotlights
lighting
15:17, 3rd Jan 2013

Dimmable Energy Saving Lightbulbs
Find out more about low energy light bulbs which can be used with standard dimmer switches
lighting
14:36, 3rd Jan 2013

Review of Megaman Energy Saving Lightbulbs
Find out more about the Megaman range of CFL energy saving lightbulbs
lighting
14:08, 3rd Jan 2013



REUK Shop

Popular Items


REUK SUPER LDR DUSK DAWN RELAY CONTROLLER
Multi-function light detector triggered light/dark dawn/dusk relay controller
£19.95 each.
Complete Circuits



KARASOULI SCC 20 CHARGE CONTROLLER
20A rated wind turbine charge controller and dump load controller with blocking diode and heatsink
£43.95 each.
Renewable Energy System Parts



2013 SOLAR PUMP CONTROLLER WITH RELAY
New solar water heating pump controller with fitted 10A relay
£25.99 each.
Complete Circuits



REUK SUPER POULTRY LIGHTING CONTROLLER
Control up to 8 Watts of LED spotlights to stimulate egg production in birds
£29.99 each.
Complete Circuits



REUK SUPER TIMER 2
User programmable 12VDC powered 16A rated repeating relay timer. 1 second to 99 hours ON and OFF times
£23.99 each.
Complete Circuits



300 WATT POWER INVERTER
Convert 12V DC battery power into 230 AC to power portable televisions, computers, video recorders etc. 300 Watt power rating - peak power 600 Watts
£29.99 each.
Renewable Energy System Parts



CONVERTED PROGRAMMABLE DIGITAL TIMER RELAY
Mains powered programmable timer converted to low voltage with relay board
£21.99 each.
Renewable Energy System Parts



12 VOLT REGULATOR
Supply a fixed 12.0 Volt DC to your devices (up to 0.7 Amp output)
£4.79 each.
Complete Circuits



MR16 CERAMIC BULB HOLDER
Bulb holder for 12 Volt LED spotlight bulbs
£1.39 each.
Energy Efficient Lighting