Let's Make a Stirplate

The last two weeks, I have been working on completing a home-built stirplate.  A stirplate allows a meadmaker (or homebrewer) to culture a larger yeast colony than what comes in the yeast packets or vials prior to pitching.  A yeast starter better acclimates the yeast to the must, and improves fermentation rates due to the healthier yeast and larger starting colony size.

My design for the stirplate is based on the one available at stirstarters.com, with a minor modification to the resistor and potentiometer.  The smallest potentiometer available at Radio Shack was 5k-Ohm, so I was forced to increase the resistor size accordingly to ensure a proper voltage drop across the fan.

The supplies (all prices at Radio Shack unless otherwise listed):

• 1 SPST Sub-Mini Switch ($3.49)
• 1 micro-F Capacitor, 2 pack ($1.99, $1 each)
• 5 k-Ohm Linear Potentiometer ($3.49)
• 680 Ohm Resistor, 5 pack ($1.49, $0.30 each)
• LM317T Voltage Regulator ($3.49)
• Breadboard ($3.49)
• 8"x6"x3" Project Box ($8.99)
• Four 3" machine screws ($1.26 x2, extra needed for additional nuts to mount fan)
• 12 V computer fan (free, salvaged from an old computer build)
• 4 D83 Neodymium Magnets (free, leftover from another project, usually $1.33 each)
• 12 V 1 Amp power adapter (free, harvested from old Verizon router)
• 22 AWG wire, soldering iron, lead free solder, electrical tape, hot glue gun (price not included)

Total price, tax included: $28.38 ($34.02 with magnets included, fan likely less than $10 additional)

Following the schematic from stirstarters, I laid out all the components and got to work building.  I highly suggest that anyone working with electronics have the appropriate multimeter, and measure the system components before soldering into place.  I should also warn you that the potentiometer will catch on fire, I repeat, it WILL catch on FIRE, if you short the voltage regulator.  Just be careful; I will not be held responsible for any accidents that occur.

Not knowing the pin layout for the LM317T and the potentiometer, I sought some help from a friend working on the same build.  You can find information on the pin layout for the LM317T here.  The potentiometer layout can be found here.  Note that you can reverse terminals on the potentiometer to control the clockwise/counterclockwise rotation of the potentiometer corresponding with an increase in power to the stirplate.  My design used the middle terminal for input, and the ground terminal as the output.  I only wired to two of the pins.  Test it out with a multimeter, and see what you prefer.

It had been years since the last time I put together an electronics project, but the build was easy enough.  First-timers shouldn't have any problem securing all the wires together.  And if soldering doesn't appeal to you, you can add some connectors to the supply list to complete the build.

           The Work Area                        Finalized wiring, Fan removed

All Screwed Together

Once finished, I put it through a test using a 1 gallon carboy filled 3/4 to the top.  Sure enough it created a steady vortex, more than enough for building a good yeast starter.  I still need to trim the potentiometer and add a knob, but looks weren't what I was going for.  It is functional, and more than capable for my needs.  Success!

Completed Project with Steady Vortex