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Magnetic Stir Plate – DIY Build

Once I had success with the temp controller, I was amped to embark on another DIY homebrew project.  For the last year or so I have been making yeast starters and nurturing them by the “every now and then” shake the flask or growler method.  Like that of the controller, I wasn’t too excited about spending a bunch of money on a magnetic stir plate.  For example, More Beer sells theirs for $99 bucks.

Again, I turned to Home Brew Talk and found a plethora of DIY builds.  I learned that almost everyone had their own style and preferences on how to mount the fan, but all the other mechanical components were basically the same.  This post on HBT was helpful for me:  Stir Plate

List of what I used:

  • Project enclosure ($6.99 – Radio Shack)
  • 3″ 12V computer fan ($15.99 – Radio Shack)
  • Rheostat 25 ohm-3 watt ($4.99 – Radio Shack)
  • Panel mount coaxial power jack Size N to match the power supply connection ($3.19 – Radio Shack)
  • Rocker switch ($3.19 – Radio Shack)
  • Silver Tone Knurled Knob ($2.99 – Radio Shack)
  • 8-32 2″ screws to secure fan to enclosure ($2.99 – Home Depot)
  • 9V power supply (Free – Old power supply from work)
  • 1 washer (Free – Had on hand at home)
  • 1 hard drive magnet (Free – Taken from an old hard drive from work)
  • Wire for additional connections (Free – Had on hand at home)
  • 1″ stir bar ($6.22 including shipping – Chang Bioscience Ebay Page)

Total cost: $46.55

I was happy with the cost savings with exception of the computer fan.  After I bought the 3″ from Radio Shack, I found that they could be had for much less online.  I stuck with the one I got and went ahead with the build.  $46 still seemed better than spending $100.

I used a step bit to drill the holes for each component.  This allowed me to make a perfectly sized hole without needing to swap out drill bits and spend time figuring out which size would be best.  The rocker switch is mounted on the left side and the rheostat is on the right.  I soldered all of the connections and wrapped with electrical tape.

Since I had no clue on how to wire this thing up, I turned to the net. This is a diagram I used to first make sure I could get the switch wired properly.

I mounted the coax power jack to the rear of the project box.  Again, used the step bit to drill a perfectly sized hole.

I centered the washer as best as possible and mounted to the fan 4 small drops of liquid nails.  After it was dry and secure, I mounted the magnet.  Although the magnet stuck pretty well to the washer, I decided to use a small amount of liquid nails to get a more solid mount.

I used 8-32 2″ flat head screws to mount the fan.  I inserted the screws from the bottom of the project box and had plenty of height to get the fan close to the top of the box.  I secured the screws to the box with 8-32 sized hex nuts and then also used washers to keep the fan raised off the base of the project box.  Lastly, I used hex nuts to complete it all and further secure the fan.

Rocker switch and rheostat installed.

Completed stir plate.

For the test run I used 1,200 ml of water.  I was pleased with the results and got a good vortex going on the first try.  Pretty stoked for the next brew day and not having to try and remember to shake the yeast starter.

This build was a little more involved for me because it had parts I had never heard of before; plus, the wiring looked more intimidating because it included a switch, fan and rheostat.  You Tube proved very helpful and also my online searches for wiring diagrams.  I was stoked that all the electrical was working perfectly the first time.


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