Power Supply unit for arduino power and breadboard

how you can take a computer u hv old (power supply unit) and turn it into a power supply that will power your Arduino and give you all the amperage you need as well as your standard 3.3 volts, 5 volts, and 12 volts for any accessories/electronics used on your breadboard And arduino power ,led 5v,12v power, fan cooling

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Step 1: What you will need

MATERIALS :
1.Computer Power Supply Unit
2.Soldering Iron + Solder
3.Male Headers
4.dc adapter power jack 2.1mm

Gelfling6 says: Apr 4, 2013. 4:29 PM

Might not work with all power supplies.. there are a few Dell supplies, which have a different wiring scheme for the ATX connector.. (PG or the constant (standby) +5V, can't remember which.) occupy the wrong pin, and connecting them will end in a loud POP as the switching IC will blow its top. (been there, done that, everyone came running, wondering why they smelled burnt epoxy.) Also, not all supplies will start off with zero load. the Arduino is hardly enough.. Some of the older ATX supplies required a minimum load to maintain the switching circuit.. a 33-ohm, 5W 'Sandbox' resistor (ceramic block, with sand/epoxy holding a wire-wound resistor), across the +5V to GND has always worked for me. The supply will see the load, but match to maintain the voltage. One more little tip, try this.. If you have an old 3.5" floppy disk drive that is fried, desolder the power connector, and keep the matching mini connector on the power supply side that matches it.. You can then, from a breadboard, run jumpers from the VCC on the arduino to +12V (Yellow), and run +5V external devices off the +5V (red).. One final tip, if the supply cooling fan draws air in, forcing it into the box, flip it around! drawing air out is more efficient for cooling..

I've converted two supplies like this myself, and run arduino, raw breadboard projects, and even a Raspberry Pi off them.
Nice thing about the ATX supply, is you have access to 3.3V, which is great if you're running projects for the Pi's GPIO bus... I still haven't put together a 3.3V<-->5V level handler, so been slowly learning to run things from the 3.3V level.

Alpha_geek says: Jul 10, 2012. 1:00 PM

One small comment: Somewhere in the Arduino specs it mentions that if the supplied input voltage is less than 7V, then they cannot guarantee 5V at the output pins, also if the supply voltage goes over 12V then you may start to cook the onboard voltage regulator. If you do need to be sure of getting 5V to the output pins on the Arduino you could either, simply splice an old USB A connector into one of the disk drive power connectors and use that for power, or supply 8.3V, 10V or even 12V directly to the power input. Other than that, thumbs up, I love hacking old pc power supplies for my little projects ... :-)

McFortner says: Jun 26, 2012. 10:00 PM

This is just what I needed for converting an old ATX power supply for use to power my 10M and 2M radios. Now I know how to wire up a switch to power the supply up. I'll take one of the 3.3v lines and connect a red LED and resistor for a power on light while I'm at it.

73 de N0YBC

thrivingon says: Jun 9, 2012. 4:57 PM

I've been using a 350W atx power supply for a few years now, well when I do electronic bread boarding stuff anyway. I use a 1/2 watt resistor (don't remember the ohms) and led on one of the +5v pins to make sure there's power before I flip the on switch for whatever I'm testing.

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Computothought says: Apr 16, 2012. 1:52 AM

That would be the perfect job for an old at power supply also. Still have an Amiga ps that has the power switch on the box. You just gave me an idea.

Gelfling6 says: Apr 26, 2012. 5:49 PM

the older Non-ATX versions, generated only +5V, +12V, -5V, & -12V, to GND.. Should still work with the same principle load across the +5V.. I have a few of the original IBM AT supplies lying around too.. Just applied one of my converted ATX units, +12V to -12V, to recharge a Razor mini Kart, (+24V system, two 12V gel cells.)

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Computothought says: Apr 27, 2012. 9:25 AM

I do to, but I also have systems than can use those old ps units.

zeros76 says: Apr 18, 2012. 4:46 PM

Very good information, utile.

Thanks.

Avadhut.Deshmukh (author) says: Apr 23, 2012. 6:27 AM

Thank you !

Gelfling6 says: Apr 24, 2012. 5:37 PM

I am curious, on most supplies, there needs to be at least a minimum load across the +5V (Not the +5vSB) to maintain the switching activity, otherwise the supply will shut-down. I've run into a few supplies, where there was a soldered-in 33-Ohm, 5W resistor across the connections on the board inside, but many others have had to add an external load, sacrificing one of the +5V (Red) & GND (Black) wires to a 10-Ohm, 10-Watt 'sandbox' (sand/epoxy filled ceramic block, with a wire-wound resistive element inside.) (I've still used 33-Ohm-5Watt versions) to maintain the load. Yes, these are a great way to recycle supplies from machines which have been scrapped down.. I've made 3 myself.

One side note, try this, it's real interesting! start-up a supply, then connect a volt meter across the various voltages, but skip the GND (Black) wires.. Yes, as example,on a supply with -5V, you can generate:

+8.3V (+3.3V, using -5V as GND)
+10V (+5V, using -5V as GND)
+15.3V (+3.3, using -12V as GND)
+18V (either +5V, or +12V and -12V or -5V as GND)
And the highest: +24V (+12V, using -12V as GND)
(the object, Not connecting the GND/Common/Black wires to anything.)

Gelfling6 says: Apr 26, 2012. 5:45 PM

There are a few more, odd-ball, but going from some of the +5 to +12, does generate a voltage, but not sure if if it registers exact +7V, or not.. Likewise, +3.3 to +5, would generate +2.8.. But, a volt meter, is better than sacrificing a project.. (at least the volt meter will say if it's good, or not, and not fry unless set tot eh wrong maximum.)

andrea biffi says: Apr 17, 2012. 5:37 AM

To anyone wants to make this, be very careful because these PSU have very hight wattage (400 W and more) and this could be lethal!
This is really interesting as know-how, but remember that a good switching psu from the Bay is very cheap, compact, and safe!

Gelfling6 says: Apr 24, 2012. 5:26 PM

Side note, I think you mean Lethal at 400W, because of the high output of the +5V & +3.3V voltages could essentially fry the thin wires on the PC-Board in an instant (If shorting the supply.).. Or, are you referring to the working voltages of the primary input side? (the filter capacitors on the Input side usually have a working voltage of 200V-DC, so yes, THIS is Lethal too!) A good rule of thumb, ALWAYS allow the supply to sit for at least 10-15 Minutes, before opening. This should provide more than ample time for the input capacitors to discharged. (most supplies have a bleeder resistor across them.) These cannot be mistaken. they're the LARGE canisters and will say anything from 200WV to 240WV for the voltage.. Yes, this IS a serious warning! contact with the pins of these capacitors, unless they've discharged will literally kick you to the floor, and could possibly stop your heart if the voltage is allowed any path across the heart. (I.E. in one hand, to the other on the other arm.)