DIY Low Cost Power Supply

A Power Supply is a most have in every decent electronic laboratory. as part of our goal, making a low cast home laboratory, we have decided to make our own personalized Power Supply which is not only economic in term of the cost but also provide several personalized features :

• Different fixed outputs : 5v, 12v, 3.3v
• Two Variable outputs : out1 : 5v to 40v, out2: 3.3v to 35v
• 2x USB outputs : for phone charging or other devices
• Good output Power : 135W (varies depending on the ATX power supply you used)

With the proper finishing, our Power Supply would look professional.

Electronic components :

• ATX Power Supply : The basic power supply that you can take from an old computer or buy and old one (most of them they still work) it provides all the basic voltages that we're going to need : 3.3V, 5V +12V.
• DC-DC Booster 100W, 6A (5V In to 35V out) (you can use better one if you like, that was the best i could find nearby)
• DC-DC Booster XL6009 4A (3V in to 35V out)
• 2x female USB port (or just use one from old devices like i did)
• ON/OFF Switch
• 6x Red Banana female connector
• 6x Black Banana female connector
• 3x Potentiometer with their covers (50kohm)
• shrinking tubes
• Green LED + 220ohm resistor
• 2x DC 100V 10A Voltmeter Ammeter (Link)

Enclosure : you can build a wooden one like mine, or chose other material.

• Wood : Thick enough to support the Power supply weight. i used two types one thick (for the bottom and the sides) and another one less thicker (plywood to easily mount component on it and lower the weight)
• Wood glue
• Wood screws
• Adhesive vinyl film for covering.

Tools :

• Caliper for precise measurements
• Jigsaw
• Soldering Iron
• Hot Glue Gun
• Electric tape

PS: Before starting anything make sure that your ATX Power supply is fully functional :

• Connect the Green cable with GND: The fan is gonna start working
• Measure the other outputs according to the scheme

-Using the ruler and the Caliper, take measurement of you power supply, make sure that the fan is not covered and you have some space for connecting everything.

- Cut the wood according to the measurements

- Get the wooden parts together using wooden glue, except the front and top sides that we're going to attach them using screws, so they will be removable for any modification in the future

- Get the measurements of the components that shall be put in the front panel :

• Female Banana connectors
• Voltmeter/ammeter screens
• USB female connectors
• Front LED
• ON/OFF Switch
• Potentiometers

Once finished, using the vinyl film cover the front and the top sides separately, then cover the rest of the box.

Mount the front panel components.

The electric circuits are easy to do, all you need to have is a good soldering iron

• Solder some wires in the inputs and outputs of each converter.
• Replace the existing potentiometer by the 50 kohm potentiometer.
• Check that the converter work as expected, and that by turning the potentiometer counter clockwise the voltage is increasing.
• Using the schems connect the rest of the cables.
• Make sure to cover all the soldering spots with shrinking tubes.

Congratulation the power supply is functional. the only thing left is finishing for a professional look.

After sanding the wooden box and taking care of it, i used some black adhesive vinyl to cover the power supply,

then i made some stickers to mark every output and button to give the power supply a professional look : you can make your own stickers or just use the files i added.

- Testing the Power supply :

Remember to carry your electric tests while making the power supply and then after it's completed

1. Turn on the power supply : check that the LED is ON
2. Using a multimeter measure the output Voltage of each output pin
3. Using a multimeter measure the output of the variable outputs and make sure that the values shown on the screen are in accordance with the measurements, otherwise tune the screen accordingly
4. Try a short-circuit (put the + and the GND together) : the power supply shall shutdown immediately and no damage shall be remarked after turn in it ON again. PS : ATX Power supply have a built in protection circuit.
5. Check the variable voltage output using a DC motor 7v to 12V motor (we are trying to check current output), start from the lowest voltage to the max rate of the motor. the Power supply shall not be shutdown at any moment (assuming that you used a good DC-DC Booster about 100W)

- Mistakes to avoid

1. Read carefully the Datasheets of the used converters and components, the withdrawal of more voltage than the specified one may cause a permanent damage to the converter.
2. Converters are important for this project, chose them wisely :-D (i screwed up 4 converters :-/ )
3. do not cover the ventilation holes or put them against the wall.

If you have any suggestion or remark feel free to add a comment. all comments will be answered ASAP