PC fan controller schematic+PCB concerns

Hi everyone,
I wanted to make myself a fan controller for my pc, since my MOBO can only controll PWM fans (4-pin) and I have only 3-pins (voltage regulated). The idea is to controll them using potentiometers and output the speed on 7-segment, 2 digit led displays (percentage or hundreds of RPM, not sure yet). So I used LM317 for the voltage regulation, arduino nano to calculate the output speed and an ICM7218CI as a LED driver, becouse I could only get common anode displays, that are blue. That’s it for the intro :slight_smile:

For the schematisc:
Voltage controller

Tacho output:

These are one of my main concerns. Will they work? I’ll also attach the full schematics, made in Eagle.

The 2nd problem is the PCB, i’ve never done one before. I can use my university’s equipment to etch or mill it. But is the attached layout any good?
Each fan has rated current of 0.09Amp (0,12A safe). The traces are 16 mills.
Is it to low for power/gnd traces? How wide should they be?Do I need to add polygons for GND? Is resistance and temperature rise the main concern, or rather the inductance and capacitance between traces?
Hopefully the last one: Will I be able to solder everything with cheap soldering iron with a tip like half cm wide, just using thin tin? Or will I have to buy/borrow a smaller one?

Excuse my English please and thanks in advance :slight_smile:

schpdf.pdf (19.1 KB)

brdpdf.pdf (39.8 KB)