#+TITLE: USB desk fan modification
#+author: Svjatoslav Agejenko
#+LANGUAGE: en

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* General
+ DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
  COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
  DESIGNS AT YOUR OWN RISK.

+ This design is released under Creative Commons Zero (CC0) license.

+ Authors:
  - Svjatoslav Agejenko
    - Homepage: https://svjatoslav.eu
    - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]

  - Valeria Agejenko

+ See also:
  - [[../../index.html][Other physical projects in this repository]]
  - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]

* Project description
End-result looks like this:

[[file:make.png]]

It all started with couple of cheap USB desk fans that were a bit too
noisy:

[[file:mini%20fan.png]]

Idea is to add DC-DC step-down converter to reduce motor voltage to
make it quieter ([[https://www.amazon.de/gp/product/B07K3W78SQ/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1][Purchased form here]]). And since I already have this
USB powered thing on my desk, why not to share this power to allow
charging of various other USB powered devices.

I ended up with this schematic:
[[file:schematic.png]]

USB power of 5 volts that enters the system via DC jack is distributed
to two USB-A connectors on the front panel. Note: USB data is not
connected. Therefore this hub is for power sharing only.

DC-DC fly-back converter could introduce voltage ripple in the
system. To smooth it out, there is capacitor (C1) and inductor (L1).

Step-down voltage converter has adjustable output voltage. So after
assembling, it can be tuned with screw-driver to reach desired
noise/airflow tradeoff.

From original fan I kept:
+ engine
+ blades
+ DC jack
+ on/off swith

Engine is attached with screws to following back-plate:

[[file:fan%20housing%20-%20fan%20mount.png]]

And result is encased into pipelike case:

[[file:fan%20housing%20-%20cover%20assembly.png]]


Download:
+ STL: [[file:fan%20housing%20-%20fan%20mount.stl][fan mount back plate]]
+ STL: [[file:fan%20housing%20-%20cover.stl][pipe-like case]]
+ [[file:fan%20housing.FCStd][FreeCAD project]]

Fan enclosure attaches to the rectangular body below using following
connector (glued to the fan housing):

[[file:fan%20housing%20connector.png]]

Download:
+ [[file:fan%20housing%20connector.stl][STL file]]
+ [[file:fan%20housing%20connector.FCStd][FreeCAD project]]

Bottom part to house 2 PCBs, on/off button and DC connector:
[[file:bottom%20stand%20body.png]]

Component attachment:
[[file:make,%202.png]]

And is closed by cover:
[[file:bottom%20stand%20cover%20assembly.png]]

Download:
+ STL: [[file:bottom%20stand%20body.stl][bottom stand body]]
+ STL: [[file:bottom%20stand%20cover.stl]]
+ [[file:bottom%20stand.FCStd][FreeCAD project]]

After assembly, it looks like this from the back:
[[file:make,%203.png]]

Note, part of the body is deformed during printing. I have heated bed
and I even printed raft support in Cura and it did not help. In my
experience black PLA filament is awful in comparison to transparent
one. Has inferior flow (results in slower print speed) and tends to
deform easily. Will never buy it again.

Fan top and bottom halves are attached using [[https://www.amazon.de/gp/product/B00OOLKD2G/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1][camera tripod quick
release screw]].