In this instructable I will show you how to make a regulated
bench power supply.
The power supply I made for this instructable is a verry small and lightweight device. As I am often not home when doing projecst (school projects, group projects etc.) I needed a small portable power supply to tests my electronic circuits.
I will explain how to make the power supply. I also will add some features you could add wich I didn’t. As last I will discuss A regulated power supply made from an old desktop computer psu.
Step 1: Parts and Tools
Most of the parts I have used I had from previous projects
or are recycled. All parts not adopted in the BOM will be featured in the instructable.
- 12DCV supply / desktop psu
- Two diodes (1N4001) (+1 for extra 5V usb output)
- LM350 voltage regulator
- 5Kohm potentiometer
- 0.1 uF ceramic capatitor
- 560 Ohm resistor
- 10 uF electrolytic capatitor
- Holder for led
- 470 ohm resistor (depending on the led)
- Toggle switch
- Some electric wires
- Cooling sink (optional)
- Led voltage meter (optional).
Extra: 5 volt usb output
- Usb connector (female)
- Lm 7805 voltage regulator
- Capacitor elco 1uF and 470 uF
If u use a desktop psu and you want a 5V usb output you will not the parts fort he 5 volt usb output (except for the connector ofcourse) as there is already a 5 v output on a desktop computer psu.
- Sanding paper
- Glue (pretty much all kind of glues will do the trick. I have used wood glue and universal glue)
A glue gun is a good option als well (this is what I used in the computer supply).
- Soldering iron
- Helping hand for soldering
- Dremel Multitool (optional!. It can come in handy if u have it)
Step 2: The Case
You will need 3 different pieces, and you need every piece
twice. All dimension I have used are shown in the picture
I have used wood from 5mm thick.
- Measure and line the different pieces.
- Cut them out a little too big.
- Tape te identical pieces of wood together
- Now you cut them to the exact size and sand the edges.
Mark on the bottom and top piece what the short side is.
Take the top piece and drill a hole in it just big enough to fit two wires.
Measure and mark the Where the holes should go for the front panel.
Measure the parts you are going to use first as they might have different dimension than the parts I have used.
Drill holes on the marked spots.
Now take the back panel, mark where the power connector should go. For cutting this piece out I used a handsaw to do the rough shape, a knife for the corners and some sanding paper as finnishing touch.
(if u want the usb output as well you have to fit o hole for the usb connector as wel)
All parts for the case are ready now.
Step 3: Electronics
First put al te parts in the front panel.
- The led and toggle switch go in the two holes above each other.
- The output connectors go in the middle holes
- There is one hole left, this is for the potentiometer.
I used extra glue for the parts in the front panel. It is not nessecary but I would recomand it.
Glue the power connector in the back panel.
Screw or glue (what you like best) to the top panel A little in front of the hole.
Turn the potentiometer all the way to the left, now you can measure between the middle pin and one of the two outside pins 0ohm. This is the outside pin you wil use. The other pin is not used.
I have connected the two capacitors and the resister for the led already on the front panel.
The led for the led is 470 ohms. I used a blue led works with 3.3volts. If u use annother type of led you can check wich resistor you need on following site: https://www.ledtuning.nl/nl/resistor-calculator , or calculate it yourself (it’s easy! Look it up.)
In the top left of the picture you can see what I already did connect on the front panel.
I didn’t use a led voltage meter as I prefer to measure the voltage using my multimeter. If you want to use a voltage meter, it has 2 wires you just have connect those to the output pins.
For the connections a soldering gun some wire and scrinkin tube. Put the scrinkin tube around the wire before you solder it!
I have connected two extra wires to the output. These wires go trough the hole in the top piece to a connector.
You should have 6 wires comming from the front pannel now. (8 if you have the usb connector as wel.)
Know make the rest of the scheme. As the circuit is verry simple I did not use a circuit board (dont hate me for this).
(if u want a usb output. This is the time to build the circuit.)
Do not connect the power connector yet. Neither connect the two extra output wires for te connector on the top panel.
Glue the side panels, front panel and bottom pannel. Use tape to keep the parts together as you glue them.
Wait for the glue to be dry. Now connect the power connector (wich is already glued in the back panel).
Now glue the back panel and top panel to the rest. Before you glue the top panel in connect the two output wires.
I have made 2 wires for the power suply with the crocodile connectors and the male bannana plugs wich fit the female bannana plugs in the front panel. The Wires could be screwed onto the bannana plugs. The crocodile connectors soldered on. Make sure to use shrinking tube.
The power supply is ready. If you are not able to find any of the parts you can easy find alternative parts. If you know the basics of electronics you can also look up the datasheets to know the requirements for alternative parts.
Step 4: Computer Supply
You can use a desktop computer power supply as well. They are
easy to find and cheap. Computer power supplies are high quality as well.
The black wires all are ground. It can be handy to bring out a couple of the ground wires.
If u need a voltage available on the power supply, bring it out and use it. It is better to use it directly than to do it trough the circuit.
For the usb connector you can dirrectly connect the connector to the 5volt (red wire).
The -5 and -12 volt have a low max current. I wouldn’t recomend using these unless realy nessecary.
If the ps-on wire (green) and the ground wire are connected the power supply is working. Put the switch between these to wires.
There is one wire wich is always on, even when the ps-on wire is not connected. This is the purple wire. It delivers 5volts I have connected this with a red led and 330 ohm resistor. The red led indicates wheater the power supply is plugged in or not.
I have connected a blue led with a 330 ohm resistor to the red wire to indicate if the power supply is switched on. I also connected a cooling fan to the 5volt wire for cooling the lm350.
Make sure there is some kind of hole in the casing so the heat can escape.
If you make a case for the computer supply make sure not to cover the holes/fans in the supply. Otherwise the power supply will overheat.
This was it If anything is not clear feel free to ask questions.