Introduction: Compact Regulated PSU - Power Supply Unit

Picture of Compact Regulated PSU - Power Supply Unit

I have already make a few PSU. At the beginning I always assumed that I need PSU with lots of Amps, but during few years of experimenting and building things I realized that i need small compact PSU with stabilize and good Voltage regulation and current limiter, that didn't take to much space on my workbench.

Like in most of my project it all started with salvage components that came in my possession.
Friend of mine gave my transformer 230V/16V from the old alarm system which is the main component of mine PSU.

Step 1: Component List

Picture of Component List

1. Transformator 230V/16 V - 1,8 A

2. Original Hiland 0-30V 2mA - 3A Adjustable DC Regulated Power Supply DIY Kit

3. Dual Red Blue LED Digital Voltmeter Ammeter Panel Volt Gauge Meter

4. DC 12V -50 to +110 Temperature Control Switch Thermostat Thermometer

5. Heat sink with fan (24VDC)

6.Voltage stabilization IC 7812

7. Lot 3MM Silver Chrome Metal Plastic LED Light Lamp Emitting Diode Bezel Holders

8. 3 x LED 3mm

9. 2 x Pot. knob

10. ATX shell

11. 24VAC power relay with 4 contact (NO-COM-NC) this is option for WELLER supply compatibility

12. Vinyl Wrap Roll

Step 2: ​ATX Housing Adaptation – Hardware Work

Picture of ​ATX Housing Adaptation – Hardware Work

When I had all components at my hand it was time for space management inside of the PSU. Because I decided to use ATX power supply housing I have to manage everything very carefully and this space planning took me lot of time.

After everything was cool, I made a front label on my PC for easier marking.

Mostly it was just drilling, the hole for ampere/volt-meter I used small drill (don’t know how it is called)

At the bottom of the housing I have mounted four of stands that I demounted from old coffee maker

Handle on the back is from the old kitchen socket, mounted with two M4 nuts with washers :)

Step 3: Schematic

Picture of Schematic

Here is schematic of the PSU (I’m not that skilled with drawing of the schematic, as you can see). If something is not clear please feel free to ask in comments, I’m realize that schematic could be done better and when I find some time I will upload better version.

I add thermostat for activating fan, when I use PSU on small current or on standby I don’t want to hear fan.
I have mounted transistor and voltage stabilization IC (7812), on the cooler.

I drilled hole for the thermostat probe into the cooler.

For mounting of the fan on the cooler I used 1.5mm copper wire and for fixing the fan and cooler onto the housing I used four 1cm standoffs.

Resistors for the LEDs are soldered directly on the 3mm LED and then isolated with shrinking tube.

Same principle is used for connecting the relays contacts

Step 4: Carbon Fibre Vinyl Wrap

Picture of Carbon Fibre Vinyl Wrap

I wanted to make a nice look for the housing, so I used Carbon Fiber Vinyl Wrap instead of painting. Also I got an idea that I could customize PSU with my signature :), I have cut my brand mark from the carton box and covered it with vinyl wrap, also I didn’t want to have unnecessary holes on the housing so I used carton box from my favorite cookies and cover the holes and also covered with vinyl wrap

Step 5: ​Front and Back Sticker

Picture of ​Front and Back Sticker

I wanted to have clear front panel, so I have design front panel on my computer (use which ever program you prefer) and printed out on printer. This is very convenient also for hardware part of drilling and cutting. Front of the sticker I have adhibit with see-through tape. Back of the sticker is adhibit with two-side tape and taped on the housing.

Step 6: Mounting Components on Front Panel and in the Housing

Picture of Mounting Components on Front Panel and in the Housing

When the housing were prepared I have started with mounting the elements on/in it. Housing consist of two parts, so for easy assembling there should be long enough wires for manipulation during the assembly.

Grounding the housing is very import, ATX usually have a ground connecting place inside the housing, check it on the photos

First I have mounted everything in the housing and start wiring everything together according the schematic. All of contacts are well soldered creating good and reliable contact and isolated with shrinking tube insulators.

Step 7: ​Calibration and Setting of the Thermostat

Picture of ​Calibration and Setting of the Thermostat

Amper/Volt meter have a small potentiometer (miniature) on the back of the panel meter, used for calibration.

After wiring everything all together calibration of the volt meter and ampere meter was necessary. With Volt meter is quite easy and accurate, I have low the voltage to the 4.5V and use the potentiometer on the back of the voltmeter to set it with my multimeter, I repeat this at 12V and 13.7V.

Calibration of the Ampere meter was little bit tricky, I have calculate current for the 5W bulb P=U*I , so that current should be at 12V I=5 / 12 = 0.416A . This is not first class ampermeter but I manage to set it nearest to the desired value, I repeat this step with 15W and 21W bulb and manage to calibrated to the nearest values, and compare this with my multimeter and it is precisely enough for normal and reliable use. Do not expect lab PSU precisely values….

Thermostat is set to activate fan at 40 C°, setting the thermostat is not very complicated and the precise instruction are on the site where I bought the thermostat. After two months of using is working ok.

Step 8: ​Interconnecting Cable for Weller Soldering Station

Picture of ​Interconnecting Cable for Weller Soldering Station

I have TCP-S Weller soldering station which have 50W /24VAC transformer what is perfect for my PSU. From old Weller handle I have harvested connector and made Interconnecting cable suitable for my PSU in case if I need more Voltage and juice.

As you can see on the schematic, for this purpose I have add 24VAC relay on the input, when the external source is added PSU automatically switch to this input what is signalized with blue LED on the front panel.

Step 9: ​Final Product

Picture of ​Final Product

It is nice PSU with small dimension, it is working fine and I am very pleased with it. Any suggestion and improvements are welcomed.


AbdallaA14 (author)2017-12-06


Thats awsom circuit,

Please can I take the calculations for Current and Voltage for this circuit?

I am student in the 4th year and I need to design this circuit as project.

please, send to me at this facebook :

Abdalla Abood(

thank u in advance

Mack937Y (author)2017-10-14

I have 120/12v transformer. I have 120 volts in my home and wish to use that transformer Do I have to change any of the listed components for 120 volt?

medzik (author)Mack937Y2017-10-15


if you use 120/12 transformer and yours household is working on 120V it will work but you will get regulation only in the range from 0V to Max. 12*1,41 = 16,92V.

All the components would work without problems, only problem could appear with the fan, in the project there is 24VDC fan and you should check the fan speed on the 16,92V, I assume that will work fine but I suggest to use 120/24V transformer for the optimal usage.

JohnE12 (author)2017-10-09

Excellent project, great idea to use an old ATX power-supply case - I'm always stumped for cases, usually end up buying a cheap aluminium box...the use of the ATX case has the advantage of supplying a switch and a power socket. Thank you, great work, and I like the way you finished the case.

medzik (author)JohnE122017-10-13

Thx for the comment

KetkA (author)2017-10-08

Hello. What a kind of sticker software did you use to do these front and
back stickers? I have not idea about what a software use. Thanks. I wait your answer.

medzik (author)KetkA2017-10-08

Hello, I used AutoCad

KetkA (author)medzik2017-10-08

Thanks! I have never used AutoCad. The result is wonderful. I made a power supply similar long time ago. You can watch it in:
It is in Spanish languaje, because I write to you from Alicante.
I am thinking into starting learning AutoCad. What a versión are you using?

medzik (author)KetkA2017-10-09

I checked out your PSU on you tube, great job , I didn't understand much comments but that doesn't matter. If you want to learn AutoCad you can download from their site, I guess first month (trial) is for free.

KetkA (author)medzik2017-10-09

yes. I am interested to do good stickers for my devices. Then I will try with AutoCad maybe 2016 versión. Wish me good luck!!!

keesj (author)2017-10-06

The pcb board of the power supply is not assembled, it is a dye kit.
This means that the resistor value have to be derived from the color code. Some of the resistor values have been printed on the pcb, but many values not.
The color code is not so bright that it can be read properly for instance purple and brown.
In the pdf manual one does'n pay attention to this and neither in the you tube film.
It is a pity one have skipped this.
Now it is useless.

medzik (author)keesj2017-10-07

Sorry to hear that, with my kit there was clearly printed values on the PCB, and then I used multimeter to define resistors values, also the colors on the resistors were clear.

KetkA (author)medzik2017-10-09

I agree with you medzik.

But you must think not all people are ready to mount this DiY kit of PCB Power Supply. I spoke about this issue to Spanish speakers into my video in Youtube. First you need to classify all components and look with a multimeter all resistors values for not to be wrong. Also you must check normal diodes and zener diodes, that have same capsulation with multimeter in Ohms to difference who are diodes and who are zeners.

If people can not difference well the components of the kit, better not to try to mount it.

OsvaldoS1 (author)2017-10-07

Great job... I will try to do one for me.. Thank you...

ron1406 (author)2017-10-06

I think in step 3 , the schematic , the green led and the blue led should be drawn in the opposite way. Now , their anode is connected to the 0 V and their cathodes go to the + (plus pole). I think this isn't going to work ....

medzik (author)ron14062017-10-07

Schematic has been updated, thank you for the information

pgs070947 (author)2017-10-05

You've lost me a bit on this.

Why do you need the complication of two power inputs?

I think I might have added a beefier capacitor on the input side to help smoothing. Check the voltage regulators data sheet to see if you need bypass caps on the ins and outs. It's good practice to have say, a 10uF and 0.1uF on both sides of the regulator for stability. Can't see any earthing either. Metal enclosures and 240-V AC needs care. Unless it's double insulated (Class 2?) it should have an earth on it.

Otherwise, good use of the ATX enclosure

medzik (author)pgs0709472017-10-05

Hy, thank you for suggestions, let me explain

Two power inputs are because I am not using voltage over 24V / 2A very often, so that this PSU satisfy my needs in 90% of time, and is not taking too much space on my workbench (Read: desk in the small apartment). But the capacity of the Voltage regulator PCB is beyond possibilities of installed transformer so I wanted to leave this option opened for me, compatibility with my weller soldering iron is a bonus, but it can easily be connected to the stronger transformer (optimal is 24VAC / 3A).

Input capacitor connected to the bridge rectifier is 3300uF what is enough for the max of 3A (1000uF per 1A).

You are right about disk capacitor 100nF on the in/out of the regulator for stability, I forgot to draw them into the schematic because I use SMD capacitors and solder them directly on the 7812, they have role of correcting fast voltage change (peaks). They are very useful for the 7812 regulator, but 7824 is used only for fan (fan will work without problems)

I forget to specified but there is a earth on the ATX housing, you can see it on the pictures (not very clear but it is there). Very good observation I have to agree that earting the metal case is essential in project like this.

pgs070947 (author)medzik2017-10-05

Still can't see the 3300uF cap.

Important things like values need to be on the schematic or in the bill of materials.

Not trying to be critical, but anything involving 230-V AC and extraneous metal (enclosure) needs to have a firm earth. I'm just worried that someone might copy as is and then gets a jolt. I appreciate that if you are using the original ATX enclosure, it will have a three pin IEC connector, but you need to stress that this earth is solidly connected to the case and ideally to the removable lid as well. A solid earth is the most important part of any equipment like this.

TechPaul (author)pgs0709472017-10-05

While there is a fuse shown in the circuit diagram , there doesn't appear to be a fuse in practice. The IEC can have a fuse but those are normally much larger than the one in the pics. Lack of earthing is also a problem with a metal case. Otherwise I'm sure it works OK

medzik (author)TechPaul2017-10-06

Thanks for comment, fuse is mounted directly on the transformer

medzik (author)pgs0709472017-10-06

Thanks for the advice, I have update schematic and mark the pictures so that it is clear that grounding is important.

3300uF is mounted on the PCB of Adjustable DC Regulated.

CharlyeZ (author)2017-10-05

Pekne si to... :-)

MilanD31 (author)2017-10-05

Mate this look excellent, I'm not shore will I make it like this but I will try and you just inspire me with your approach.

TerryC111 (author)2017-10-05

Could you explain where to buy the Carbon Fiber Vinyl Wrap? I am not familiar with this product. Otherwise, this is a great project and passing on your legwork for finding the necessary items from Banggood is perfect as I use them a lot. Thank you for your effort.

medzik (author)TerryC1112017-10-05

Thank you for comments, I have added link in components list, but it is available also on the ebay , aliexpress ....

MateuszI (author)TerryC1112017-10-05

You can find them on ebay, they come in different colours. Its purely just an aesthetic thing from the looks of it. But really does finish this project off. Love the look of it.

billbillt (author)2017-10-05


JeffreyR37 (author)2017-10-05

Very nice instructable. Well done and look forward to building this.

aroneggens (author)2017-10-05

Nice project, looking forward to seeing more projects like this!

FrontierShed (author)2017-10-02

Beautifully done! It looks like an off the shelf unit. I really like the carbon fibre finish.

medzik (author)FrontierShed2017-10-02

Thanks for the comment, I forgot to mention that I use hair dryer for the carbon fibre finish.

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