Every full-fledged tinkerer in electronics needs a variable power supply, and, as a tinkerer prefers to do, usually builds it instead of just buying. Personally, I did it because I didn't want to spend money on it, eventually discovering that now my PSU has a unique combination of features that no money can by. In this write-up I'll attempt to provide the reader with a comprehensive step-by-step guide on how to build something similar (and probably looking less like crap 😀 )
I based my design on this splendid homemade PSU:
|Made by ThomasVDD|
Since I didn't have access to a laser cutter and couldn't be bothered cutting the box manually with a jigsaw, I just found a plasic box of sufficient size and cut some holes in it.
My PSU was supposed to be a carbon copy of the one on the link above (and I certainly wouldn't write this if it stayed this way). This model has some added features like:
- Separate ground terminal with ammeter (0-1A and 0-5A range - selectable)
- 2 additional terminals to measure and display zener diode's voltage
- A display that shows voltage at variable voltage terminal
- Additional -5V terminal
- A switch that lets you measure current through USB port
- Awful exterior
What you'll need
- Working ATX Power supply
- Some enclosure
- A matching number of banana plugs and terminals (not exactly matching, based on my experience you never need more than 4 connection leads at once, so probably just 4 plugs and at least 9 terminals)
|Banana terminals that I used.|
Not the only kind at the market,
you're free to choose something fancier.
- 7 fuse holders and fuses
- 2 voltmeters with 3 wires (Power, Ground and Signal aka measured voltage) - most voltmeters sold on Aliexpress are 2-wired meaning they measure the voltage of the power source. You don't need them - as soon as voltage drops below 4.5V they will switch off.
- USB port - I found that the easiest in procurement panel-mounted USB connector is "USB Female to Female cable" (BTW most suppliers incorrectly list it as type B):
- 2 Ammeters - 0..1A and 0..5A
|Analog is the way to go!|
- For variable voltage circuit you will need: LM317, some filtering capacitors, 1.2k Ohm resistor, 10k Ohm potentiometer, 1N4007 (or similar) diode, heatsink for LM317, screw terminals (x3).
- Miscellaneous: 2 SPDT switches (changeover), 1 SPST switch (on/off), 1k resistor, a couple of screws and standoffs to attach voltmeters to the enclosure.
|This "item list" picture was relevant when I started working|
on the original PSU, since then I replaced ugly usb ports
and added lots of features. Still, this picture is inspiring so I'll just leave it here.
BuildingHere's the schematic for the whole project.
- VV1 and 2 are voltmeters
- To build LM317 circuit check the original article(step 3). It's basically the same.
A picture is worth a thousand words, so here's some pictures of build in progress:
|4) Plan ahead, make a grid according to which you'll place|
your posts and fuse holders. Note a huge analog ammeter
on top center - got fried in less than a month.
|Aaaand there goes the cheap chinese ammeter...|
|At least it works without it just fine.|