12/27/2025 11 AM - Found parts

The reason I wanted to make this project was to experiment with electronics, but getting an exact voltage and current is annoying.

When I looked online, I saw 300 W power supplies on AliExpress for around $40, so I figured I could do it cheaper myself.

My plan was to use a switching power supply with constant voltage, then add a buck converter to step the voltage down and control the current.

I decided to go with the LRS-350-36 for now, though that might change later. (since it is kinda expensive)
For the buck converter, I searched through a lot of options on AliExpress but couldn’t find a good one with high enough amperage. I kept seeing these 300W 9A converters, but I wanted more current. Then I stumbled across a 300w 20a buck converter also known as the SZBK07. That was good enough for my needs.
I found a voltmeter that would work nicely.

Random image of the buck converter

12/27/2025 1 PM - ac power and stuff

In any good power supply, there is always a switch.
So I looked for one and I came up with this. It is a standard SPST switch and it'll work just fine.
I orginally was just thinking of a pigtail cord for the AC input. I decided that a C13/C14 plug would be more versatile because you can plug and unplug it from the actual device (and it's cheaper than the pigtail too)!
I chose this for the actual panel, and this as the cable.

input:

12/27/2025 3 PM - output ports

Now I had to figure out what the output was going to be. Originally I just planned to attach 2 stripped wires to the end, but that would be kinda hard to use. So instead I decided to use alligator clips.
I chose to use 4mm banana jacks.
I looked through many types. At first, I found this terminal and this jack.
After, I found some that were paired.
I thought they would work nicely, but when I looked at the alligator clips, I realized it would be easier to have these banana plug sockets since they fit nicely with these alligator clips and could be removed easily.

idk product image

12/28/2025 9 AM - refining parts

When I was looking for some Mean Well LRS 350 36, they were all pretty expensive. I considered a buck-boost module instead of just a buck module, so I could run it on a lower voltage power supply (which were cheaper). However, I couldn't find any high-power ones that fit my needs.
I also considered having a boost converter then a buck converter, but that would be inefficient and lower the maximum output.

Then, RIGHT BEFORE i was going to publish it, I found this 48V 480W power supply. Not only was it more than we needed, it was also CHEAPER!
To fully use this to the maximum wattage, I decided that it would be smart to upgrade the buck converter too. I looked through many different converters (mainly 500w and 600w), and found that these 600w buck converters could take the 48v and turn it as low as 2.5v.

12/28/2025 1 PM - ammeter, voltmeter, wiring diagram

Voltmeter problems

When I was working on the wiring diagram, I realized that the voltmeter / ammeter I chose before wouldn't cut it since it doesn't come with a shunt. I found two alternatives this and this. They are virtually the same but they come with shunts. Now I had to figure out how to actually wire it. Luckily, I found a schematic online that basically told me how to do it.
Then I had another problem. When looking at the meter's specs, I found that the working voltage was from 4.5V-30V. This was bad, because my voltage would be 48V, way over the limit. The only practical way to solve this would be to add another buck converter. The hard part was to find a buck converter that had a high enough input voltage. I stumbled across this board which could take up to 100V. Also this one which was adjustable.
Whatever board I chose, I decided to go with 12V output since it met the voltmeter requirements and because it would make adding fans easier. (if i do decide to add some fans).

Wiring Diagram:

12/28/2025 6 PM - fans + cooling

I found these 80x80x25mm fans that worked for 12v. They would fit my needs nicely. I just had to figure out how to power them on when it got hot.
I settled for these thermal switches at 40*C and normally open. I chose 40 degrees C because that was the maximum operating temperature of the power supply.

When deciding to add 2 fans or just 1, I calculated that there would be at least 50W at heat when running on high loads. That is a lot of heat, so I decided use 2 fans. One fan would be intake, one would exaust.
I also considered where to place the thermal switches. I figured one would go on the psu, and the other on the buck converter, since they were the main generators of heat. Then, I would OR their outputs together.

Updated wiring diagram:

12/28/2025 7 PM - buck converter dilemma

When looking over my materials, I found that the 600W buck converter had an output voltage from 2.5V-38V (in my case), and had a minimum output amperage of 1A. When I looked at a 500W converter, it had more control, able to go from 1.9V-46V and current from 0.3A. However, the drawback (of course), was that it was only rated for 400W continuous, which was quite a bit lower than I'd like it.

I'll have to consider this more later

12/28/2025 8 PM - Found better parts, first parts list

I looked through the parts I've found in the past and organized it into a single list. I also had to replace some parts since they were too expensive or needed shipping:

• the C13 cable: way too expensive
• the thermal switch: shipping
• the 80x80x25 fans: too large, had to replace them with 60x60x15
• rocker switch: used a larger version

I also organized it based on section for conviencience (ur welcome).
also btw i updated the wiring diagram to use more specific names
another update I figured the 600W converter would be better since not many devices are even sub 2.5V**

Parts List

Input

• 1x of Power Supply Cable 3-Prong 1.2m, TYPE USA, PRICE $3.49
• 1x of IEC320 C14/C13 Panel Socket, TYPE Type 4/China Mainland, PRICE $1.33
• 1x of KCD1 Rocker Switch SPST, TYPE 15X20mm/5PCS, PRICE $2.39
• 1x of 48V 10A Switching Power Supply 480W, TYPE N/A, PRICE $26.99

Cooling

• 2x of 60mm 12V DC Cooling Fan, TYPE 6015/12V, PRICE $2.61
• 2x of Thermal Switch KSD-01F, TYPE 40C/H (Normally Open), PRICE $1.33
• 1x of DC-DC Buck Converter 60V 3A, TYPE 2–34V, PRICE $2.79

Output

• 1x of 600W DC-DC Buck Converter CC/CV, TYPE N/A, PRICE $11.62
• 1x of DC Voltmeter Ammeter 0–100V 50A, TYPE Red Blue With Shunt, PRICE $3.98
• 1x of 4mm Banana Jack Panel Mount, TYPE Black/1PCS, PRICE $1.26
• 1x of 4mm Banana Jack Panel Mount, TYPE Red/1PCS, PRICE $0.99
• 1x of Banana to Alligator Test Leads 90cm, TYPE N/A, PRICE $3.04

New diagram:

12/29/2025 8:33 AM - cadding

I spent a long time caddingthe case for the box.
While cadding, I had to fix a few things (and noticed some):

1. The power supply took up most of the space, so the case should only be a little bigger than that.
2. The 80×80×25 mm fans were too large to fit in the compact case, so I switched them to 60×60×15 mm.
3. When compared to everything else, the rocker switch was far too small, so I switched to a larger one to make it easier to use.

Here’s what I did:

1. Created the dimensions of the box
2. Outlined the text on the front
3. Created cutouts for the fans
4. Created cutouts for the switch and power input on the back
5. Cut out parts for the display and outlets on the front

However, there was one issue I didn’t realize at first: the potentiometers used to adjust current and voltage were on the board and were extremely small and hard to reach, so they needed to be made more accessible.
I don't have a good solution right now.

12/29/2025 8:57 AM - potentiometer

The best I can think of is to take them out of the buck converter, but that'll still be difficult to use, since the knobs are minuscule.
I tried to find potentiometers with knobs, but there were very few. They also have a low rating and are kinda annoying since I don't want a pile of pots I'll never use.
I then had the brilliant idea to search for 3d models of knobs to print them out, and I found this thing! But the problem was that it needed a 4mm shaft with the potentiometer to work.
Then I found this, this, and this

Then I changed the cad to reflect this.

12/29/2025 10 AM - last touches to github

did some last touches to the github before i submit, hopefully it'll be approved.

• added cad model + image
• added wiring diagram
• added bom.csv
• touched up readme.md

1/3/2026 - Completely redid the whole cad

uh also note to reviewers I really dont want to spend the time redesigning these complex modules

I completely overhauled the CAD model, and I replaced all of the blank slots with the real models of components. I added these components:

• 600w buck converter (replaced)
• KCD1 switch
• voltmeter / ammeter
• 2x 60x60x15 fans
• c14 panel plug

To fit this, I had to increase the width by 0.5 inches and the depth by 1 inch. I also had to slightly reposition a few existing parts to maintain proper clearance. Each adjustment needed testing and alignment.
(also added to the github + added new image folder)

But, after like 5 hours of hard hard work, I bring to you: the new BEAUTIFUL CAD

1/5/2026 1 PM - microcontroller + all the other parts

they want me to do more work, so here i am, adding a microcontroller.

At first, when I was thinking about this yesterday, I thought the microcontroller would be great at measuring temperature then controlling the fans with pwm so it wasn't just on or off.
This was cool, sure, but it seemed lame to use a WHOLE microcontroller on it.

Then, later, I also thought of wiring up my own voltage and current sensor (voltmeter / ammeter), and display everything on a screen (temps, fan speed, voltage, current, wattage)
But this took a lot of time to accept, since I didn't want to throw away my old components (the voltmeter / ammeter)

So, I looked for some parts that would do the trick:

• A TFT LCD screen. 2.0 inch or this 3.5
• Now I need something to measure voltage + current. I was searching for a long time, and then I found the INA series. There are a lot of different variations, but the INA228 was optimal, since it allowed for 85V / 20A measurements. This is the best I found: https://www.aliexpress.us/item/3256810323201401.html.
• I looked a long time for a temperature sensor. I was deciding between the DHT22 and the AHT20. The DHT22 had a higher range from -40 to 125 (85 for the AHT20), but it had worse resolution (0.5 vs 0.3), so I went with the AHT20. This one would be great: https://www.aliexpress.us/item/3256806795952050.html
• For the actual controller, I think an ESP32 will be fine. https://www.aliexpress.us/item/3256805767190776.html

1/5/2026 3 PM - new wiring diagram

yeah so i did the new wiring diagram
this was very painful to give up all the time i spent researching how to wire that stupid digital ammeter / voltmeter and the thermal switches and basically everything

also, for the fans, I'll need to use 4-pin fans with pwm control otherwise there's no point in a microcontroller. I found these: https://www.aliexpress.us/item/2251832835370376.html (they are more expensive though)

Let's also find a 5V buck converter so I can power all of the little sensors. luckily, the same one as last time will do: https://www.aliexpress.us/item/3256806811379418.html
The only little problem is that we'll need one for both 5v and 12v. I checked the max current, and all of the sensors + display shouldn't exceed it.

However, I think there may be a problem where I2C is too slow, since it is trying to communicate with all 4 i2c devices, and the screen is really large.

This literally took forever, trying to figure out all the pins for the new parts.

i guess i just have to fix the cad now :(

1/5/2026 6 PM - fix cad + wiring diagram

fixing wiring stuff

before I thought that the lcd display needed to use i2c, but I figured out that spi would also work. I chose to switch it since it's faster and doesn't have any devices on it

Also, I realized that since I have 2 of the exact same temperature sensors, their i2c address will be the same, which will cause issues, so i might have to get a multiplexer.

new cad for the 3.5 inch screen

this took more work than i thought. at first I thought I would just change the dimensions of the rectangle in the sketch, but no. I had to make the box a little wider to make it look good, since the new screen was a little bigger. (so now width is 6.5 inches, depth is 12.5)

also you may have noticed I put the output on the bottom and the adjustment on top now :) (i thought it looked better and more symmetrical that way)

back view:

1/5/2026 9 PM - a lot of stuff and code

fixing temp sensor

because im lazy, instead of using a multiplexer (which I considered for a while), I decided to use a sht40 temperature sensor (also i2c, also pretty accurate) with a AHT20+BMP280
yeah its kinda bad but whatever

pwm issues

then i was looking back and I also found that the 3.3v from the esp32 was probably NOT going to work for the pwm.
:( very sad i know
so I searched online and found the IRLZ44N, which is a nice logic level mosfet that will work great for my purposes of a pwm. note this was undid

then i realized, that I was doing too much, and that was only for a 2 pin fan.
I searched for a tutorial, and found this video, it said that 3.3v logic is fine for a fan so i had to undo my 45 minutes of work.

also I wired up the tachometer pin to the esp32 because I figured it would be better since it allows detection of stall and reading rpm.

while coding, I changed up the wires to the display once again and I also changed the intake fans pins from 1 & 3 to 16 & 17 so I could download code while they were plugged in

final wiring diagram, i hope:

coding

the hardest part was just getting the display code and reading through that stinky documentation.
and all the sensors documenation were pretty awful, and I had to figure out how to use all of them.

luckily, it only took like 3 hours before I got a version that might or might not work

please accept reviewers
code is on github
features:

• Reads temperature (AHT20 + SHT40) and humidity.
• Measures voltage, current, and power (INA228).
• Controls two fans with PID-based PWM to reach target temperature.
• Monitors fan RPMs and detects fan failure.
• TFT display shows all measurements, fan status, and system alerts with color coding (normal/warning/critical).
• Updates sensors every 2s, RPM every 1s.
  

1/10/2026 - last bom update

so i took a little break from this, but im back now, and hopefully it gets approved

part changes + additions

when making the new bom, i also looked for some new fans (btw i cant find any 60x60x15 so 60x60x10 will do)

• https://www.aliexpress.us/item/2255800737378210.html (this one is new but only 1pcs shopper)
• https://www.aliexpress.us/item/3256806285412293.html (but needs 7$ shipping)
• https://www.aliexpress.us/item/2251832835370376.html (original - 1pcs per shopper) so to fix this, i have to get 1 of both options 1 and 3 what is this chopped ahh project bro

also: I selected some cheap 22awg silicone wire to connect small components like the potentiometer
decided that multiplexer probably not needed, since after researching default addresses for a while, I found that they shouldn't conflict.

more - a lil research also brought me to this: https://www.aliexpress.us/item/3256807060355465.html (a cheaper cord)

fuses: I've forgotten about the fuse, and I'm expecting max 20a, so a 25A fuse is reasonable: https://www.aliexpress.us/item/3256806057525580.html?
also removed the temp sensor and the digital voltmeter and ammeter, since im replacing that with the esp32 microcontroller

not only that, I think I've also forgotten about them heatsinks, so i plopped that in too - these will be good for cooling other hot parts like the lil buck converters and maybe the esp32: https://www.aliexpress.us/item/2251832663311102.html

btw i reorganized the bom since there were so many out of place parts, turned it into a csv too and shoved it into github. also updated the cad images this is hella repetitive

so here's the bom:

Cooling

• 1x of 60x60x10mm PWM Fan (Delta EFB0612HHA), TYPE standard 4pin/6010/EFB0612HHA, PRICE $3.96: https://www.aliexpress.com/item/2255800737378210.html
• 1x of 60x60x10mm PWM Fan (ADDA AD06012HX10AB00), TYPE Standard 4PIN PWM/black/NO RGB, PRICE $5.98: https://www.aliexpress.com/item/2251832835370376.html
• 1x of 50pcs/lot Aluminum Heatsink 8.88.85mm Electronic Chip Radiator Cooler w/ Thermal for IC,3D Printer, TYPE N/A, PRICE $2.42: https://www.aliexpress.com/item/2251832663311102.html

Sensors + Modules

• 1x of SHT40 Temperature & Humidity Sensor Module, TYPE SHT40/China Mainland, PRICE $2.14: https://www.aliexpress.com/item/3256809091535018.html
• 1x of AHT20 + BMP280 Temp/Humidity/Pressure Sensor, TYPE Module, PRICE $1.63: https://www.aliexpress.com/item/3256806795952050.html
• 1x of ESP32 WROOM-32 Dev Board (USB-C), TYPE 1PCS-CP2102 TYPE-C, PRICE $0.99: https://www.aliexpress.com/item/3256805767190776.html
• 1x of INA228 Voltage/Current/Power Monitor Module, TYPE 228 welding, PRICE $5.70: https://www.aliexpress.com/item/3256810323201401.html
• 1x of 3.5" TFT LCD Screen (ST7796, 320x480), TYPE N/A, PRICE $7.56: https://www.aliexpress.com/item/3256809650697406.html
• 1x of Adjustable Buck Converter 60V 3A, TYPE 2-34V, PRICE $3.33: https://www.aliexpress.com/item/3256806811379418.html
• 1x of Buck Converter 60V 3A (5V Output), TYPE 5V, PRICE $3.25: https://www.aliexpress.com/item/3256806811379418.html
• 1x of Buck Converter 60V 3A (12V Output), TYPE 12V, PRICE $3.34: https://www.aliexpress.com/item/3256806811379418.html
• 1x of 600W CC/CV Buck Converter (12–75V Input), TYPE N/A, PRICE $11.66: https://www.aliexpress.com/item/3256807619950116.html

Power + Wires

• 1x of 5Pcs Circuit Breaker Overload Protector Switch Fuse 3A 4A 5A 8A 10A 12A 15A 18A 20A 25A 30A Resettable 220V with Waterproof Cap, TYPE 5pcs/25A, PRICE $5.42: https://www.aliexpress.com/item/3256806057525580.html
• 1x of IEC C13 AC Power Cable (USA Plug, 1.2m), TYPE USA, PRICE $3.50: https://www.aliexpress.com/item/3256807060355465.html
• 1x of IEC C14 Panel Mount AC Socket, TYPE Type 4/China Mainland, PRICE $1.34: https://www.aliexpress.com/item/3256808473935736.html
• 1x of 4mm Banana Jack Panel Mount (Red), TYPE Red/1PCS, PRICE $1.34: https://www.aliexpress.com/item/3256805937948099.html
• 1x of 4mm Banana Jack Panel Mount (Black), TYPE black/1PCS, PRICE $1.26: https://www.aliexpress.com/item/3256805937948099.html
• 1x of Banana Plug to Alligator Clip Test Leads (20A, 90cm), TYPE N/A, PRICE $3.05: https://www.aliexpress.com/item/3256806675649321.html
• 1x of KCD1 Rocker Switch SPST, TYPE KCD1 15X20mm/5PCS, PRICE $2.40: https://www.aliexpress.com/item/3256808591861621.html
• 1x of 22 AWG Silicone Wire (4 colors, 25ft each), TYPE 22 gauge silicone wire each color 25ft, PRICE $9.98: https://www.amazon.com/gp/product/B07HGT44XY/
• 1x of 48V 10A Switching Power Supply (480W), TYPE N/A, PRICE $26.99: https://www.amazon.com/gp/product/B096VJMQFM/

new wiring diagram

added fuse into it

2/18/2026 - Made a kicad schematic

took like 3 hrs of my life, but at least i got to learn about the kicad symbol maker tool
the only hard part of doing this was to find the proper symbol for each thing. honestly i just found a random one with the right pins and renamed it. and i had to make my own lcd screen with the symbol maker tool
please dont make me do anything anymore

3/8/2026 - made a lid

so i cadded a very nice snap lid:

the only problem i had was that i couldn't really fit the snapping part in the front so i only used 3 (not 4)
also, the back snapping point is a little close to my fan, but it should have enough clearance (in the cad at least)

With lid on final assembly (electronics still inside ofc):

so i uploaded this to the github with new images and we're done now