My only Fan!

Case fan mount.

I prefer to use low-voltage DC for my projects and private home-wiring (I am qualified to work with non-fixed mains equipment, but obviously don't touch the stuff unless I have to). My industrial-control background inclines to me preferring the 24-28V range over 5V-USB-Power, mainly because it lets me push more power down the wire a bit more efficently. It also allows me to directly tap my 24V backup-power battery and bypass the inherent ineficiency of the 230V inverter for equipment that doesn't need it.

I'm actually in two minds about my home-DC voltage. 5V-USB-Power is enough for most of what I run directly off DC, and things are readily available for that voltage these days. Plus it is really simple to wire up a micro-controller to drive things at 5V without the need for level converters, if I want to go all 'smart' device. But there is still at least one important device in my life which needs the full 28V, and at an amperage above what even 28V USB-C Power-Delivery can pump, so I have the raw 28V available on-tap anyway.

I had tried a 12/24V car fan in my appartment, but it was so cheap and badly-balanced it sounded like an aircraft engine! Instead I designed and 3D-printed a mounting bracket for a nice quiet fluid-bearing 120mm case-fan rated for 24V, which I powered via a 6-35V PCM motor speed controller such as available online for a few bucks, in a cavity within the fan enclosure:

Sample PCM controller.

I mounted it on a ball-joint arm intended for attaching small cameras on walls, also purchased for a few bucks online. And on the front and back, some metal grills I had saved off some old equipment.

It is quiet enough that I can leave it running (turned down a bit, if needed) while sleeping under its gentle air-flow in the summer.

Blender, and strait stl files for the brave, are here. Public domain, no warranties.


Air Exchanger.

Here is another fan, or two fans, actually. No fancy-pantsy 3D-print this time, just cut wood. This one fits in the edge of my window. The top fan vents air outside from the top of the room (where hot air, being lighter, accumulates) and the bottom fan draws in (hopefully) cooler air.

Window air-exchanger bar.

I put a nice push-button switch on it, even with a fan icon! LED-lit so I can find it in the dark to turn it off if I wake too cold late at night.