If you are into electronics then you may be knowing that a proper variable lab bench power supply has its own benefits for example testing your DIY circuits, knowing the forward voltage of a high power led, charging batteries and this list goes on-n-on, but those variable lab bench power supplies can be soo expensive to buy around 50-300 dollars and things starts getting worst when you have to pay that much when you need only some common voltage rails like 3.3V, 5V, 12V.but there is a cheap alternative to that, you can build your own DIY lab bench power supply that will give you some common voltage rails like 3.3V,5V,12V using an old ATX SMPS from any old computer, and it will cost around 10-15 Dollars depending on your availability of stuff, for me it was 5 Dollars because i got an old ATX SMPS from my friend. so, before starting this project you should also ask your friends for old computer from where you can scavenge one SMPS from it, let's get started...
Step 1: Stuffs Required
THE CORE STUFFS
1) ATX SMPS X 1
2) Binding posts X 5
3) AC Switch X 6
4) LED X 2
5) Power Resistor X 1
6) Heat Shrink
7) Wires ( 12-14 AWG)
8) Banana plug
It should look beautiful like an commercial product for so let's add some LED lighting and premium carbon-fiber looks to it and remember it is fully optional and is nothing to do with it's functionality...
THE OPTIONAL STUFFS
1) LED Strips X 4
2) plastic standoffs X 4
AND FINALLY YOU NEED SOME BASICS HAND AND POWER TOOLS
Step 2: Let's Build It
WARNING:-if this is your first experience with AC mains voltage, then stop doing this project and do rather simple projects first to gain some experience.
THIS AC MAINS VOLTAGE CAN POTENTIALLY KILL YOU, SO BE CAREFUL!!!!!
Before start opening the case of ATX power supply first keep the power supply unpluged for atleast 3 days to discharge those high voltage capacitors with that been said, let's get started.
First open the case of ATX power supply and clean the internal electronics with a brush or blower.
Step 3: Preparing Output Wires
Now make a bunch of wires of same color and cut the wires into shorter length.
Step 4: Planning Place for the Components
Mark the holes for the binding post, power indication LED, standby indication LED and AC switch ,then drill the holes .
Step 5: Attaching Binding Posts
Mount the Binding post in the holes and fix them in place using epoxy or two compound adhesive.
NOTE:-Before soldering wires to binding post separate 5 black wire (GND) and 1 red wire (+5V) and 1 yellow wire (+12V) and one red wire (+5V) or yellow wire (+12V) or orange wire (+3.3V) depending upon your model if your smps deliver most of the power on +12V rail then separate yellow wire, if on +3.3V rail then separate one orange wire and if on +5V rail then separate one red wire.
Step 6: Soldering Wires to the Binding Posts
Now, solder all the wires to respective binding posts (except for those 8 wires that i told you to separate), and use as much heat shrink tubing as you can to protect any bare contact point shorting with chassis and other solder joints.
NOTE:- if your SMPS has Brown (+3.3V sense) ,pink (+5V sense) ,yellow (+12V sense) all of smaller gauges then solder them to their respective voltage rail, they are sense wire and must be connected to respective voltage rails to give a positive feedback to SMPS in order to get clean regulated output.
Step 7: Mounting Power on Switch
Now mount the AC switch using bolt and secure it firmly and then solder the green (standby wire) and one of the black wire (GND) from separated once to it and protect the joint using heat shrink.
Step 8: Mounting Indicator LEDs
Next, mount the power indication (red) LED and standby indication (green) LED to their respective holes and then solder a 500 ohm resistor to its anode (+) and protect the joint with heat shrink tube and then apply some hot glue at the led from the terminal side to fix them firmly, then solder black (GND) wire to both LED's cathode and solder the purple (Vsb) wire to resistor of the standby (red) LED and red (+5V) wire to the resistor of the power indication (green) LED.
Step 9: Adding a Dummy Load
Now find a space inside your SMPS to mount the power resistor ( i recommend mounting it on the chassis so to dissipate heat alot quickly or to the heat sink of the power mosfets, in my case i had a lot of space on the heat sink so i mounted there) using some kapton tape or electrical insulation tape and solder one of the black (GND) wire from the separated onces and any one wire from the voltage rail to which your smps deliver most of the power (in my case it was +12V) to the terminals of the power resistor and protect the solder joint using heat shrink tube.
IF YOU ARE NOT INTERESTED IN MAKING IT LOOK PREMIUM AND GORGEOUS THEN YOU CAN SIMPLY PUT THE TOP COVER ON AND SECURE IT WITH NUTS AND YOU ARE GOOD TO GO BECAUSE AFTER THIS ONLY DECORATION IS LEFT ALL ELECTRIC WORK IS COMPLETED AND YOU SMPS IS NOW FULLY FUNCTIONAL AND NOW YOU CAN CALL IT AS A FIXED OUTPUT LAB BENCH POWER SUPPLY.
Step 10: Covering With Vinyl
Now, cut the appropriate size of carbon fiber vinyl ( or any of your choice) and apply on SMPS body and don't forget to cut the holes for the binding posts, LED's, mains input terminal and exhaust fan when applying in order to get proper finish.
Step 11: Let's Give It a Stand
Now, attach the plastic standoffs at the base using epoxy or fast glue.
Step 12: Mounting LED Strips
Next, mount LED strips at the base in what ever quantity you want ( in my case i have attached 6 in the front and 3 on remaining each sides then connect then in parallel as written on the LED strip ( + of first LED strip to + to second LED strip and vice versa) and then, solder the last black wire (GND) and yellow wire (+12V) to any one LED strip's + and - and protect the solder joints using heat shrink (other will get power on there own because they are connected in series).
Step 13: Reassembling and Testing
At last close the chassis and tight with the screws provided.
AND IT IS DONE NOW YOU CAN PLUG THE AC MAINS INPUT AND THEN YOU SHOULD SEE THAT THE STANDBY INDICATION LED (RED) SHOULD BE GLOWING AND WHEN YOU TURN ON THE SWITCH THAT WE MOUNTED ON THE CHASSIS THEN YOU SHOULD GET THE VOLTAGES IN THERE RESPECTIVE RAILS AND POWER INDICATION LED (GREEN) SHOULD TURN ON ALONG WITH THE LED STRIPS, IF NOT THEN MAKE SURE THAT THE CONNECTIONS ARE GOOD OR NOT.
Step 14: After Completion
Here are some pictures so to make you get a better understanding of what i am doing here and in case i've missed some steps to mention this pictures can help you.
Now for the connectors just attach 14AWG wire of length of your choice to it and on the other side attach alligator clip.
Step 15: Some Random Pictures
AND IF HAVE ANY QUESTIONS REGARDING THIS POWER SUPPLY THEN PLEASE COMMENT DOWN BELOW IN THE COMMENT SECTION, I WILL FEEL HAPPY TO HELP YOU.
UNTIL THEN MAKE AWESOME PROJECTS, INSPIRE THE WORLD WITH OUR AWESOME IDEAS AND I WILL SEE YOU NEXT TIME.