This design is based on T12 Compatible Soldering Station and its firmware is modified STM32 Soldering Station Firmware.

Both of soldering tips are controlled by their own PID software regulators, i.e. independently.

Let me thank again to David, who takes care of the project! He does a really great job and his permission allowed me to modify firmware.

From 3D printing point of view, just panel has changed - stl file is possible to download below. The entire box with battery adapter is available at original design site: T12 Compatible Soldering Station.

I bought the soldering tweezers from AliExpress shop.

In the following pictures and links, you can see and download all the important documents and supportive files ...

Schematics:

Layout:

Bill of materials: Soldering_Tweezers_10_BOM.pdf

Gerber files for controller: Soldering_Tweezers_10_Gerber.zip

The modified firmware (version 1.13.10): STM32SolderingTweezers.hex

Updated panel stl file for 3D print: Soldering_Tweezers_Panel.stl

You can see temperature of first soldering tip on the display as big number, temperature of second soldering tip is indicated as difference from first one (by smaller font). In case of need, there is also option in menu for disbalancing soldering tips between each other ("EDIT TIPS" - "TWEEZERS" - "t2 diff.", where "TWEEZERS" name can be modified by user).

I tested the station successfully, and it works as expected.