Hello everyone, this is my first post there which makes me glad to join your community

Over two months ago I started working on my project (guys, do you know that feeling when it's Christmas Eve and all of a sudden you realized that you want to make a DIY soldering station and you can't stop thinking of it?), the aim was to make a solder station which I was leaking of and teach myself a lot of new things with especially analog electronic (till 1 year ago I was fully into high-level programming on PCs and smartphones).
The very first thing I did is I choose proper (at least I think so) soldering iron, it took few hours to dig into their specifications and do some compartments. Finally I came with a soldering iron from Solomon SL30 ESD-CMC for 50 PLN (4,3 PLN = 1 EUR, so 11 EUR / 13 USD) which did pretty good impression on me (and that was the first day I realized that electronics things with "ESD" in name are my catch-phrase like "sugar-free" for someone else etc). If you want, here's a quick look how does it look like inside:





More specs: it's a 24 V iron with thermocouple inside heater, 48 W, up to 480 Celsius degrees, ESD-safe, ceramic heater, 5-pin connector (TC+, TC-, GND, HEATER-1, HEATER-2).
The next problem for me was a power source. I found few toroidal transformers, however every single one was 12 V. I decided to unwound secondary winding and rewound it by myself, using galvanized wire from some kind of DC motor. I created two separate 12 V windings that could be connected in series to give 24 V:




Next part of the project was the digital and analog circuity prototyping, I'm already familiar with AVR microprocessors and I decided to use ATmega16 due to 16 KB flash memory that is required to handle pretty large 128x64 LCD controlled by ST9720 driver, with using of u8g library. Little quick showoff how it was looking:



Some mess around, as big as my personal life was consumed by this project

At this moment, let's have a little stop and discuss few things. I've created working prototype, however I definitely wouldn't call it fully successful. I made several design mistakes, especially thermocouple circuit - there is no cold junction compensation and there are multiple different metals - soldering station's socket&plug, ARK connector. Also, there is 620 Ohm resistor pulled to opamp's non-inverting input to compensate opamp's offset voltage. That one possibly creates a voltage divider with thermocouple's wire, which is definitely not good.
Why wouldn't I spend more time on improving it? I could work in this project for months improving every single thing, making it closer to perfect. However, I lack of good quality measurement tools, and time. Also I'm still a beginner in electronics who is keeping developing as fast as lack of good measurement and production tools can limit me

. I wanted to finish this project and go with another one.
Anyway, there's schematic and two-layer PCB layout. I did some PCB projects in past like motion-sensitive LED tape dimmer or accelerometer interface, and several others - so this one was pretty big for me.


IMPORTANT NOTICE: LM7805 capacitors was 1000 uF and 470 uF, not 2x 4700 uF
The production process was most entertaining thing for me, I pretty really enjoyed it. I used thermotransfer method and etched a PCB in sodium persulfate. Before it was etched, I had to drill drills because of my drill is very cheap one (

) and keeps bursting thin etched tracks. Especially with 0.4 drills that I've used..
Here are some pictures of production and assembly. I used case from broken ATX power supply to place components in:







Translation of screen content:
Soldering station v1
Target: 170
Temperature: 164
Current power: 30 perc
Consumed current: 635 Wh
(total) Work time: 12 hours
and current hour with ambient temperature - I put RTC in this box

I think that's all guys

Thanks for reading and feel free to comment, I'm open for suggestions. Don't blame me so much

Yours,
Adrian