My First PCB: Air Conditioning Fan

green light and fan pcb plugged in

As you may know, I enjoy making various personal air conditioning systems using old computer fans and the Arduino. In order to try making my first printed circuit board (PCB), I designed a personal air conditioning fan system that plugs into any standard USB port, and can be powered via computer USB or 5V wall adapter. Except for the printed circuit board etching kit my dad gave me for Christmas, pretty much every component I used was salvaged from old electronics (this is seriously low budget!).

usb fan circuit_schem

Basically, a fan is connected to and on-off switch to act as air conditioning. An RGB LED can be lit either green or blue, and a slide potentiometer both changes the color and adjusts the brightness.

parts to fan light circuit pcb copy
The parts used for the circuit.

Here’s the components I used, plus their sources:

  • Standard DC toy motor, from an old electric toothbrush
  • CA RGB LED, an old one that I had burnt the red lead out, so only the green and blue diodes worked
  • Black LED collar, from an indicator LED on an old computer tower (doesn’t do anything, just makes the RGB look cool)
  • 3-pin slide switch, from a broken ‘build your own plastic mechanical spider’ kit that my brother had
  • 3-pin slide 250K Ohm slide potentiometer, from an old space-age toy gun
  • 470 ohm resistor
  • USB-Type A to USB-Mini cable, from some old LeapFrog toy (I cut off one end and left only the Vcc and GND lines of the remaining wire)
  • 3D printed fan blades (I tested two different ones, and I’m working on designing my own)
My initial sketches for the layout of the board.
My initial sketches for the layout of the board.

I prototyped the circuit with a breadboard first, and then designed the PCB layout on paper, making it as space efficient as possible. Then I cut a 1×1 inch square (5×5 cm) from a larger piece of copper board, added the ‘wires’, or the black rub-on stickers that prevent parts of the copper surface of the board from being removed.

Partially etched PCB.
Partially etched PCB.

Next was to actually etch the board by putting into a solution. After doing some research, I found that you can use a mixture of vinegar, hydrogen peroxide, and salt, instead of the standard ferric chloride etching solution. Household chemicals are safer to use and won’t burn your skin if you spill it! I added equal parts vinegar and hydrogen peroxide, placed the board in the solution, and then sprinkled coarse salt on top.

Overall, it took about eight hours for all the excess copper to dissolve. I changed the solution twice, as the reaction slowed down as the solution dissolved the copper. The second time I added a higher concentration of vinegar, because it seemed to speed up the reaction more than the hydrogen peroxide or salt.

Some of the tools I used.
Some of the tools I used.

With the board etched, I used my dad’s drill press to drill holes for the components, and some steel wool to remove the black etching lines. Using my dad’s improvised soldering iron (a woodburning tool, a little high temp, but worked okay), I had my first experience soldering components to a board! The end result was decent, though it took me a long time to do it.

The two fan blades I tested out.
The two fan blades I tested out.

The last step was getting a fan blade for the DC motor. I printed two different fan models to test, and I’m working on my own right now. The green one below looks much fancier, but it moves significantly less air than the blue fan. It also has sharp edges, and I cut my fingers on the spinning blades more than once. I may print a scaled up version of the blue fan when I get the chance.

Prototype of my fan blade design made in Tinkercad.
Prototype of my fan blade design made in Tinkercad.
The finished circuit laid out.
The finished circuit board laid out.

Since the circuitry and parts have been gathered and put together, I now have to make some kind of case for the whole thing. Right now, the fan is practically unusable because the motor can’t stay upright. I could 3D design a case, make some kind of insulated wire stand, or make something with wood and cardboard.

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