Prices Today for a lab power supply well exceed $180. But it turns out a obsolete computer power supply is perfect for the job instead. With these costing you only $25 and having short circuit protection, thermal protection, Overload protection and varied output voltages of 3v, 5v and 12v but we will me modifying it to give out 1.5v to 24v. They are perfect for general electronics.
This is my first Instructable for what I think is a brilliant idea, I'm only 14 and i can build it
WARNING: This will void warranty's and can shock you if you don't have your wits about you
NOTE: This Tutorial is littered with bad grammar and spelling mistakes. English Teachers may want to look away now
Your going to need:
Tape
Screw Driver
Computer PSU (I recommend 250W+)
PSU Cable
Wire Snaps
Soldering Iron
A 10ohm, 10W or greater power resistor (Some new power supply's don't work properly without some load so this can provide that)
Optional:
Switch
2 LEDs of any colour (Red and Green is the best)
If your using the leds you need a 1 or 2 330 OEM Resistor(s)
Heat Shrink Tubing
External Enclosure (Some people cram it all inside the Power supply case or you can put it in a external enclosure.)
These Depend on which method you use: (More on that later):
Terminal Blocks
Drill
LM317 or LM338K Voltage regulator
100nF Capacitors (ceramic or tantalum)
1uF Capacitors Electrolytic
1N4001 or 1N4002 Power Diode
120 Ohm resistor
5k Ohm variable resistor
Binding Posts
Crocodile Clips
This is my first Instructable for what I think is a brilliant idea, I'm only 14 and i can build it
WARNING: This will void warranty's and can shock you if you don't have your wits about you
NOTE: This Tutorial is littered with bad grammar and spelling mistakes. English Teachers may want to look away now
Your going to need:
Tape
Screw Driver
Computer PSU (I recommend 250W+)
PSU Cable
Wire Snaps
Soldering Iron
A 10ohm, 10W or greater power resistor (Some new power supply's don't work properly without some load so this can provide that)
Optional:
Switch
2 LEDs of any colour (Red and Green is the best)
If your using the leds you need a 1 or 2 330 OEM Resistor(s)
Heat Shrink Tubing
External Enclosure (Some people cram it all inside the Power supply case or you can put it in a external enclosure.)
These Depend on which method you use: (More on that later):
Terminal Blocks
Drill
LM317 or LM338K Voltage regulator
100nF Capacitors (ceramic or tantalum)
1uF Capacitors Electrolytic
1N4001 or 1N4002 Power Diode
120 Ohm resistor
5k Ohm variable resistor
Binding Posts
Crocodile Clips
Step 1: Harvesting & Preping The Power Supply
Warnings:
BEFORE WE CONTINUE MAKE SURE YOUR POWER SUPPLY IS UNPLUGGED.
Capacitors can bite and if not give a painful shock kill you. Please discharge the power supply by letting it sit unconnected for a few days or connecting a 10ohm resistor between the red and black wires.
If you hear buzzing when you turn on the power supply it means there is a short or another serious problem. If you hear buzzing (that not coming from the soldering iron) when soldiering it mean your power supply is on. There is still power flowing through the PSU if it plugged in but not switched on
OK lets get straight into it remove the computer case and take out the screws (usually 4) at the back of the computer to release the power supply. Now take out the 4 screws on top of the case and take the wires out of the hole then group wires of the same colour together and snip off the ends.
Just To tell you , you've just void your warranty
BEFORE WE CONTINUE MAKE SURE YOUR POWER SUPPLY IS UNPLUGGED.
Capacitors can bite and if not give a painful shock kill you. Please discharge the power supply by letting it sit unconnected for a few days or connecting a 10ohm resistor between the red and black wires.
If you hear buzzing when you turn on the power supply it means there is a short or another serious problem. If you hear buzzing (that not coming from the soldering iron) when soldiering it mean your power supply is on. There is still power flowing through the PSU if it plugged in but not switched on
OK lets get straight into it remove the computer case and take out the screws (usually 4) at the back of the computer to release the power supply. Now take out the 4 screws on top of the case and take the wires out of the hole then group wires of the same colour together and snip off the ends.
Just To tell you , you've just void your warranty
Step 2: Wiring It all Up!
Now comes the tricky part, this is were we really get into it and add LED's and switches and other such objects. There are alot of each type of wire so I recommend using 2-4 of each type. Some people cram everything inside the box i used another external enclosure but it depends which method you use in the next step.
If you want to add a Standby or a Mains On LED then you will need a LED (Reds recommended but not a necessity) and a 330 Ohm Resistor. Solder a black wire to one end of the resistor and the short leg of the LED to the other. The resistor will reduce the voltage down to stop it damaging the LED. Before you soldier the other one on optionally slip on a little bit of heat shrink tubing to stop shorts. Solder the purple wire to the longer leg and when you plug it in but don't turn it on, it should light.
You can also have another LED (Green Works Best) to light when you turn the PSU on. Some say to use the grey wire for the power for the LED but you need another 330 Ohm resistor. I just connected it to the orange 3.3v wire.
If you are using the Grey wire:
Before you solder it on slip another bit of heat shrink tubing over it to stop shorts. Solder the grey wire to one end of the resistor and the other end of the resistor to the longer leg of the LED and a black wire the the shorter leg.
If using the Orange 3.3v Wire:
Before you solder it on slip yet another bit of heat shrink tubing over it to stop shorts. Solder the orange wire to the longer leg of the LED and a black wire the the shorter leg.
Now for the switch, if you have one on the back of your PSU i suppose you don't really need this but i think you should still use it regardless. Connect the Green wire to one contact on the switch and a black to the other. If your really against using a switch then just tape together the green and black wires.
You can also use a 1 amp fuse. All you do it get the clump of black wires you'll be using and cut them somewhere along the wire and then bridge them with a fuse in a fuse holder.
Some Power supply's need a load to work properly. To provide this load solder a red wire to one end of a 10 ohm, 10 watt resistor and a black wire to the other. This will trick the power supply into thinking its powering something.
If this is all confusing there is a diagram attached to help. The diagram shows the binding post method to connect the wires. I will explain more about these in the next step. It also connects the grey wire to the Power on LED but you can also use the orange wire and it also shows the wiring for the high wattage resistor.
If you want to add a Standby or a Mains On LED then you will need a LED (Reds recommended but not a necessity) and a 330 Ohm Resistor. Solder a black wire to one end of the resistor and the short leg of the LED to the other. The resistor will reduce the voltage down to stop it damaging the LED. Before you soldier the other one on optionally slip on a little bit of heat shrink tubing to stop shorts. Solder the purple wire to the longer leg and when you plug it in but don't turn it on, it should light.
You can also have another LED (Green Works Best) to light when you turn the PSU on. Some say to use the grey wire for the power for the LED but you need another 330 Ohm resistor. I just connected it to the orange 3.3v wire.
If you are using the Grey wire:
Before you solder it on slip another bit of heat shrink tubing over it to stop shorts. Solder the grey wire to one end of the resistor and the other end of the resistor to the longer leg of the LED and a black wire the the shorter leg.
If using the Orange 3.3v Wire:
Before you solder it on slip yet another bit of heat shrink tubing over it to stop shorts. Solder the orange wire to the longer leg of the LED and a black wire the the shorter leg.
Now for the switch, if you have one on the back of your PSU i suppose you don't really need this but i think you should still use it regardless. Connect the Green wire to one contact on the switch and a black to the other. If your really against using a switch then just tape together the green and black wires.
You can also use a 1 amp fuse. All you do it get the clump of black wires you'll be using and cut them somewhere along the wire and then bridge them with a fuse in a fuse holder.
Some Power supply's need a load to work properly. To provide this load solder a red wire to one end of a 10 ohm, 10 watt resistor and a black wire to the other. This will trick the power supply into thinking its powering something.
If this is all confusing there is a diagram attached to help. The diagram shows the binding post method to connect the wires. I will explain more about these in the next step. It also connects the grey wire to the Power on LED but you can also use the orange wire and it also shows the wiring for the high wattage resistor.
Step 3: Presenting The Power
OK from all the other tutorials I've read there are a lot of different methods of connectors for connecting your devices to the power, Ill start with the best one and work my way down to the worst.
Some tutorials will tell you to stuff it all inside the one case but that is dangerous and will make it very warm and crushed. I recommend using a external enclosure.
1.Adding a Variable Resistor:
I personally think this is the best method as this can provide any voltage between 1.5 to 24 volts. The reason that its 22v and not 12 is because it uses the Blue wire which is -12 volts not the common earth (black wire). You will need:
LM317 or LM338K Voltage regulator
100nF Capacitors (ceramic or tantalum)
1uF Capacitors Electrolytic
1N4001 or 1N4002 Power Diode
120 Ohm resistor
1x 5k Ohm variable resistor
First build the circuit from the main picture and connect your +12 and -12 volt lines. Now drill holes in either the power supply or an external case to fit the variable resistor, All the other circuitry should be kept inside. I suggest now adding Two terminal blocks so you can wire devices directly in. You could also connect some alligator clips in to the terminal blocks aswell. When you turn the variable resistor the voltage should range between 1.5 and 24 volts. NOTE:There is a typo in the main picture it should read +24v variable instead of 22v. If you had an old volt meter you could wire it in to the output so it can tell you what voltage you are at.
2. Binding Posts
2nd is using binding posts to connect equipment. First drill hole for the binding posts (make sure to wrap the circuit board up in plastic as metal shards can short circuit it) then check they are the right size by inserting the posts and tightening the bolt behind them. You chose what voltage to hook up to what post and how many posts to put in. The colour Codes for all the wires are:
Red: +5v
Yellow: +12v
Orange: +3.3v
Black: Earth/Ground
White: -5v
There is a image below using the binding post method.
3.Basic Crocodile Clips
If you don't have that much experience or don't have the above parts and for some reason can't buy them you can just hook up whatever voltages you want to Crocodile clips. If you do chose this option I would suggest a sleeve over the Crocodile clips to prevent short circuits.
Tips and Troubleshooting:
- Dont be a bit afraid to spice the box up a bit, you could add leds, stickers or anything!
-Make sure you are using a ATX Power Supply. If it is a AT or older power supply it will most likely have a different colour scheme for the wires. Unless you have some data on the wiring dont attempt this as you could get caught on the wrong end of a wire and get your head blown off.
- PSU means Power Supply Unit
-If the LED on the front doesn't come on chances are you have the leg wired up the wrong way around just switch the wires on the legs and it should light.
-Some modern Power supply's will have a "sense wire" this has to be connected to power for the Power supply to function. If the wire is grey connect it to an orange wire, if it is pink connect it to a red wire.
-The High wattage power resistor can become quite hot; you could use a heatsink to cool it down but make sure it doesn't short anything out.
-If you insist on putting everything inside, you can put the fan on the outside rather then the inside.
-The PSU fan can be noisy , it is powered by 12v. Since it isn't power computers anymore and doesn't heat up as much you can snip the red wire of the fan and connect the orange 3.3v wire. Keep an eye on your circuit after you do this, if it produces too much heat connect the fan back up to the red wire.
CONGRADS You have successfully finished your Power supply!
Thanks to other tutorials on Wikihow and Instructables because I used some of there pictures.
If you have any questions email me at prod_lad@hotmail.co.uk
Some tutorials will tell you to stuff it all inside the one case but that is dangerous and will make it very warm and crushed. I recommend using a external enclosure.
1.Adding a Variable Resistor:
I personally think this is the best method as this can provide any voltage between 1.5 to 24 volts. The reason that its 22v and not 12 is because it uses the Blue wire which is -12 volts not the common earth (black wire). You will need:
LM317 or LM338K Voltage regulator
100nF Capacitors (ceramic or tantalum)
1uF Capacitors Electrolytic
1N4001 or 1N4002 Power Diode
120 Ohm resistor
1x 5k Ohm variable resistor
First build the circuit from the main picture and connect your +12 and -12 volt lines. Now drill holes in either the power supply or an external case to fit the variable resistor, All the other circuitry should be kept inside. I suggest now adding Two terminal blocks so you can wire devices directly in. You could also connect some alligator clips in to the terminal blocks aswell. When you turn the variable resistor the voltage should range between 1.5 and 24 volts. NOTE:There is a typo in the main picture it should read +24v variable instead of 22v. If you had an old volt meter you could wire it in to the output so it can tell you what voltage you are at.
2. Binding Posts
2nd is using binding posts to connect equipment. First drill hole for the binding posts (make sure to wrap the circuit board up in plastic as metal shards can short circuit it) then check they are the right size by inserting the posts and tightening the bolt behind them. You chose what voltage to hook up to what post and how many posts to put in. The colour Codes for all the wires are:
Red: +5v
Yellow: +12v
Orange: +3.3v
Black: Earth/Ground
White: -5v
There is a image below using the binding post method.
3.Basic Crocodile Clips
If you don't have that much experience or don't have the above parts and for some reason can't buy them you can just hook up whatever voltages you want to Crocodile clips. If you do chose this option I would suggest a sleeve over the Crocodile clips to prevent short circuits.
Tips and Troubleshooting:
- Dont be a bit afraid to spice the box up a bit, you could add leds, stickers or anything!
-Make sure you are using a ATX Power Supply. If it is a AT or older power supply it will most likely have a different colour scheme for the wires. Unless you have some data on the wiring dont attempt this as you could get caught on the wrong end of a wire and get your head blown off.
- PSU means Power Supply Unit
-If the LED on the front doesn't come on chances are you have the leg wired up the wrong way around just switch the wires on the legs and it should light.
-Some modern Power supply's will have a "sense wire" this has to be connected to power for the Power supply to function. If the wire is grey connect it to an orange wire, if it is pink connect it to a red wire.
-The High wattage power resistor can become quite hot; you could use a heatsink to cool it down but make sure it doesn't short anything out.
-If you insist on putting everything inside, you can put the fan on the outside rather then the inside.
-The PSU fan can be noisy , it is powered by 12v. Since it isn't power computers anymore and doesn't heat up as much you can snip the red wire of the fan and connect the orange 3.3v wire. Keep an eye on your circuit after you do this, if it produces too much heat connect the fan back up to the red wire.
CONGRADS You have successfully finished your Power supply!
Thanks to other tutorials on Wikihow and Instructables because I used some of there pictures.
If you have any questions email me at prod_lad@hotmail.co.uk
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-5v, -12v or +5v, +12v? what are those? and whats with the plus, minus? i thought 12v was 12 v?
How would these read on a tester? I want to use this mainly to power an Electrolyte Rust Removal tank (13 gallon tub) and it really only needs to be like, 12v dc with about 2 amps... But for Amps, the more I can safely get, the better I guess. With 2A I'd most likly be leaving it running for up to 8 hrs at a clip. Thoughts? I have a Delll, 305W PSU its like a P/N: N305N-00 or something like that. please see my next comment...
Pin Number, Voltage / Name, Color of Wire.
1 +3.3 VDC* Orange
2 +3.3 VDC* Orange
3 COM Black
4 +5VDC Red
5 COM Black
6 +5 VDC Red
7 COM Black
8 P_OK Gray
9 +5 VFP Purple (Whats VFP?)
10 +12 VBDC White (Whats VBDC?)
11 +12 VBDC White
12 +3.3 VDC* Orange
13 +3.3 VDC*/SE* Orange
14 ? 12 VDC Blue
15 COM Black
16 PS-ON Green
17 COM Black
18 COM Black
19 COM Black
20 NA NA
21 +5 VDC Red
22 +5 VDC Red
23 +5 VDC Red
24 COM Black
*The orange +3.3 VDC output wires must be 16 AWG. The +3.3 VDC terminals are high current type (9 A current rating/Molex-HCS type).
*The +3.3VDC/SE is a brown sense wire for +3.3VDC and is optional.
Do I use ALL the wires? take every black wire and put them together, every red, every orange, blue (well, blue with a white stripe)... ? also, do i use a 10w, 10 ohm resistor or do i need a bigger one? thanks!
Thank u
What do I do with them?
Any help would be great.
Thanks,
E
I've made a few supplies, +/-12V, +5V, +3.3V (No -5V.) out of the 200W supplies from a bunch of old Optiplex desktops.. usually use a 30-Ohm, 5W resistor across the +5. Been able to run gadget projects, Amateur Radio equipment, (with little to NO noise, surprisingly.) external hard drives, even charge Gel-Cell batteries from them.
It also depends on the condition of the supply... Brand New? Pulled from a working computer? or pulled from a failed computer? If the last, suspect even the supply may be bad, and NOT a good candidate for conversion. (See remark below I made to Coolinst, about the one that went up in smoke.)
There are some circuits for ( http://img.photobucket.com/albums/v472/n1np/local/manual_fan_controller.jpg for example) for manual control, but thermal control would require making a circuit that uses a thermal varister in place of the potentiometer... most of the time, I'd simply leave the noisy fan be, as it's doing its job, and unless noise is a problem (needing quiet for recording, etc.) it's not worth baking the supply, but slowing the fan.
Most supplies have a built-in speed control now, and the last few supplies I've converted, I replaced the straight-wired fan with a thermal circuit & fan (if it fits) from another supply I've scrapped.
I am putting one of these together and have come across something that I might be getting wrong....
In mocking up the LM317 circuit in breadboard, I have got the thing metering -11v to +11v??? I am using one of the black ground wires on the black side of the volt meter, but cant figure out why I am not just getting positive voltages??? Could the diode be faulty? Or is this in fact correct?
Any help appreciated...
The way you are measuring, it is correct.
reg set for max: meas +22var(actual +23)-->R1-->R2--> -12-->psu gnd= +11v
reg set for min: meas +22var(actual +1)-->R1-->R2--> -12-->psu gnd= -11v
0V has to become new gnd or (0V adj)
Brilliant instructable I am new in electronic engineering and wanted a lab power supply will you please tell me that how Can we connect a potetiometer(voltage regulator),rheostat, voltmeter and ammeter in atx power supply to calculate and vary voltage and current?
Thanks
http://www.antennex.com/preview/archive3/powers.htm