I made a few small updates to the air purifier to finish it off.

New lid

To reduce sound from the air moving through the holes, I made a new lid design:

I like this design less, as it exposes more of the internal to the external view, but the result gives a more pleasant sound.

$fn=100;

translate([-5,-190/2,0]){
cube([10,190,2]);
}
translate([-190/2,-5,0]){
cube([190,10,2]);
}
difference()
{
    union()
    {
        //cube([150,150,3],center=true);

        cylinder(d=200,h=2,$fn=100);
        translate([0,0,2]){
            cylinder(d=190,h=2,$fn=100);
        }
    }


	difference()
	{
		cylinder(d=70,h=4);
		cylinder(d=60,h=4);
	}

	difference()
	{
		cylinder(d=90,h=4);
		cylinder(d=80,h=4);
	}

	difference()
	{
		cylinder(d=110,h=4);
		cylinder(d=100,h=4);
	}

	difference()
	{
		cylinder(d=130,h=4);
		cylinder(d=120,h=4);
	}
	difference()
	{
		cylinder(d=150,h=4);
		cylinder(d=140,h=4);
	}
	difference()
	{
		cylinder(d=170,h=4);
		cylinder(d=160,h=4);
	}
}

Fuse

Given the components I picked off my desk are over dimensioned and I use a standard 5V 3A wall plug to drive it, I decided to add a fuse holder and 2.5A fuse. If the mosfet fails to short, or the esp fails and closes the mosfet we have an practical short. The internal resistance of the coil + mosfet is < 0.1 Ohm and I don’t want to test the safety of the wall plug.

Extra input capacitors and better diode

I added some extra capacitors on the input and inserted an actual diode (I found on a for-parts pcb lying on my desk) as diode.

Efficiency

I did a quick test on efficiency, On the used range I get around 62-84% efficiency in the converter. Not great but good enough for its purpose. Maybe I will profile it at some point.