DIY Stir Plate

February 24, 2011 § 1 Comment

Hi Everyone!

It’s been awhile, my apologies.  I haven’t posted in awhile because I’ve been extremely busy; school, work, brews, it can get hectic quick!  But, as promised here is how to make your very own magnetic stir plate for yeast propagation. I promise it’s cheap and nearly painless.

What you will need:

A non-metal box Free I used a Frisbee, of course.
LED toggle switch $1.99 RadioShack
Control knob $2.99 RadioShack
Electrical tape $1.99 RadioShack
Potentiometer/rheostat $3.99 RadioShack
6-12 Volt power supply Free checkout your old small appliance chargers.
Computer fan Free easily retrieved from a scrapped CPU
Rare earth magnet Free I took a hammer and crow bar to a hard drive for this one.  Honestly, to hell with those little screws.  Who the hell has those little screwdriver anyway?)

Total =    $10.96

Tools to have on hand

  • Wire cutters/strippers
  • Drill & Bits
  • Gorilla Glue

Now that we have procured everything it is time to assemble.  Many sites that I checked out while trying to figure this project out had piss poor assembly instructions, I will try my best to do better.

The Fan:

First you want to secure your extracted rare earth magnet to the center of your computer fan.  I did this with a dab of gorilla glue.  Make sure it is as centered as possible or else you will have an obnoxious wobble.  Next you want to take the red and black wires coming from the fan and strip them with your wire cutters; snip any others at the source (mine was blue.)  Next, you want to cut your power supply cord down by the appliance plug end and strip the ends.  Test your wire polarities and mark the rest of your power supply cord accordingly; red is positive and black is negative.  You will want to remember this for the rest of your parts.

The Rheostat:

A rheostat is an electrical appliance used to raise or lower the resistance of a circuit correspondingly to decrease or increase the current flowing.  This piece has three terminals at the top and a resistance knob on the front.  First you will want to cut your power supply line again.  Be sparing when you cut your line, measure comparatively to your box, you still want some to make it to the wall.  For all references left to right assume we are looking on the rheostat from the knob side with the terminals pointing up.  Take your power supply positive and connect it to the far left terminal, this is your main power.  The negative from the power supply will go on the far right, this is the ground terminal.  Next you will strip the lines coming from your fan.  Connect your positive to the center terminal, this is the resistor knob and will control speed.  The negative will be connected to the far right, ground terminal.  Now plug your power supply in and test your fan.  Play with the knob and make sure everything works.

The Toggle Switch:

The toggle switch is designed just like the rheostat with a power, ACC, and ground terminal; no worries, these are all marked accordingly on the product.  Your power supply positive goes to the power terminal. Power supply negative goes to the ground.  Positive coming from the rheostat goes to the ACC, this is the switch.  The negative from the rheostat goes to the ground terminal.  Again, test your new switch, make sure it works all fancy like with your rheostat.

The Prestige:

Now you will connect your positives and negatives and tape them up.  Next, wrap all of your open connections thoroughly with electrical tape.  Drill holes for your rheostat knob, toggle switch, and power supply accordingly.  Set all of your pieces and make sure they fit snugly.  Consolodate any loose wiring with electrical tape, make sure nothing is in the way of your fan.  Now you will want to center your fan on the base of the box with the magnet facing toward where you will be placing your beaker.  I used a piece of cardboard as a buffer so that my fan moves freely, and easily glued this into place.  Some people like to use bolts and wood and fancy stuff; I say keep it simple.  Let the glue set.  Then, flip it over, connect your control knob to the rheostat knob, plug it in, and bask in the beauty that is your own, homemade, stir plate.  Be proud, it’s yours.

This is how my finished product came out.  Notice the round rheostat and the rectangular LED switch.  Also how I ran the wires around the fan and consolidate them with electrical tape.

Of course I had to rep!

For information about making a yeast starter and propagating yeast pay Mr. Malty a visit.

Have fun with this project and let me know if you have any issues (

To your health,



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