Introduction: Super Cheap Variable Power Supply
I have been yearning for a variable power supply for some time now so I thought I just would dive headfirst
all in all, this cost me 30 dollars
start with the power brick
I used a Lenovo power brick (20v)
but any brand will work, the higher the better since the voltage regulator cant increase the voltage, so the voltage of the power brick will be the limit of your power supply
the Lenovo cable was different than a normal cable, it had the negative in a ring around the positive cable.
hp power supplies use 3 cables in their wires, just ignore the thin one (often blue)
in general, any power brick will work so you can have a lot of leeways.
: laptop power brick 13-24 volt range (preferably 1.5 amps)
: LM2596S(vma 404) adjustable voltage regulator (i got mine from Kjell and company for 10 dollars)
: digital voltmeter (optional) got mine from Kjell and company for 10 dollars
: connectors (optional) I used RCA connectors I had laying around
: soldering station
: project box
Step 1: Striping the Cabeles
strip the cable on the power brick so you have a positive and negative (double-check)
Step 2: Prepair the Voltage Regulator (optional)
this is if you want an external voltage knob
begin by desoldering the old potentiometer from the converter and replace it with a 3 pin header
then solder on 3 jumper cables to the header
continuing in a later step
Step 3: Conecting Input and Output Cabeles to the Regulator
start by getting 4 cables in about 2-3 dm lengths and attach them to the input and output of the regulator.
keep in mind you will be pumping upwards of 20 volts at 2.5 amps thro these cables so don't use normal jumper cables.
Step 4: Adding Probes for the Voltage Dissplay.
connect 2 jumper cables to the output of the converter to later connect to the voltage display
you can use thinner cables here because the display is not using as much power.
Step 5: Prepair the Front Pannel
start by drilling a large hole where you want your voltage display and trimming it to size with a file.
then drill the desired amounts of holes
I needed 4
one for the output jack
one for the potentiometer
and two for switches (you only need one if you have a 50k ohm potentiometer, more on that later)
Step 6: Conecting Output Jack
push in the jack in the front panel and tread thro the negative terminal and nut as shown.
then solder on the positive to the center terminal and skrew on the nut (make sure the negative terminal is on)
and then connect the negative to the negative terminal.
Step 7: Attach the Potentiometer to the Front Panel
just glue it on if you have the model I have or if you have the other model (other picture) you screw it in as you screwed in the RCA jack
Step 8: Solder the Potentiometer (those Who Have a 50k Ohm Potentiometer)
make sure the middle pin is connected to the center pin on the header you attached in an earlier step.
the outer pins don't matter which way there attached if you desire a different direction to increase the voltage when turning the knop you switch the outer pins.
Step 9: Conecting the Potentiomer (those With 45 - 47 K Ohms Potentiomer)
these flavors of potentiometers where the only one I could find locally so I came up with a solution
when just using a 45k ohm potentiometer the regulator can only reach 13 volts so I attach a 5k ohm (3k if you have a 47k ohm potentiometer) resistor to the center pin with a bypass switch so I can access the lower voltages (see diagram)(this is why I have one more hole on the front pannel)
Step 10: Adding a Power Switch
shorten the positive input on the voltage regulator and splice in the switch as shown
Step 11: Conect the Power Brick
connect the negative to negative and positive to positive.
I added some electrical tape later to avoid shorts
Step 12: Conecting the Voltage Display
fuse together the yellow (sometimes white) voltage probe with the red wire witch supplies power to the unit (make sure your display can handle the maximum voltage of your power supply.
and connect it to the jumper we connected earlier to the voltage converter remember to get the polarity right
ps. remember to tread the cables thro the hole you made
and push it thro to lock it in
Step 13: Fit Everything in the Case
I stuck down louse cables with universal glue and fastened the power brick with double-sided tape
Step 14: Done Plus Wireing Diagram
close up the lid and see if it works
Step 15: More Stable Output
thanks to a comment by a helpful Redditor adding this to the output will reduce noise
these components can often be found on computer parts.
credit to: u/spakecdk