diy stir plate

I’ve been hearing and reading from a lot of sources that a making a yeast starter is another powerful tool to make great beer. Giving your yeast ample time to multiply and activate before you pitch is essential to meet proper pitching rates for both store-bought packs and cakes recovered from your primary of a previous batch. In a nutshell a stir plate is used to aerate the starter wort/yeast mixture by spinning a magnetic bar inside the flask. This action keeps the yeast in suspension and continuously mixes oxygen into the mixture. Oxygen – while bad for the beer (aka starter wort) – is an important growth nutrient.

Personally, I am using the plate to start-up a cake I had recovered and washed from a previous primary. It’s been in the refrigerator for about two weeks, so this process (I let them stir and multiply overnight) makes them ready to pitch later during brewday.

Making your own stir plate is simple. The tools you’ll need are a screwdriver or two, drill (with bits), superglue and a soldering iron. I followed instructions or pictures from these following sites: via Homebrewtalk, via David Trumbel, via Beertools. Given that I had a few of this items laying around, this all in all cost me approximately $25.


Parts

• 1 – 4″ PC DC Fan (check the voltage, make sure it will match what you’re feeding it)
• 1 – Project Box Radio Shack #270-1806
• 1 – Rocker Switch Radio Shack – #275-694
• 1 – Knurled Knob Radio Shack – #274-424
• 1 – 25 Ohm Rehostat Radio Shack – #271-265
• 1 – 12v DC Power Supply (old cell phone/camera charger)
• 1 – Rare Earth Magnet from old PC Hard Drive or decent magnets
• Wire (you’ll use under a foot)
• Some way to stabilize the fan (I superglued it to a small, empty spice container)
• Magnetic stir bar (you can find these cheap online)
  

Costruction

1. Drill holes for on/off switch, power supply wire, rehostat in the project box. Ensure everything fits properly.

2. Prepare the fan wires; mine had PC power supply hookups so I did not have to strip the wires.

3. Prepare the power supply wires. Snip the end with the device plug in adapter. Now to quote Homebrew talk user Anthony Lopez “Some phone chargers will have two wires, while others I’ve found have a “braid” going around another insulated wire. The “braid” is our ground or negative and the inner cable is your power side. For the chargers with 2 single wires inside, black is your ground.”

4. Connect the ground (black) of the power supply to the ground (black) of the fan.

5. Solder the male end of the power supply wires (red or striped) and solder it to the top terminal of the power switch (may be labled supply). If you have it oriented correctly (the ‘O’ on the bottom for off) this is usually the top terminal on the back of the switch. Here is a decent picture of that.

6. Connect the other terminal of the power switch (may be labled load) to the middle arm of the rehostat using a short length of wire. Solder it in.

7. Almost done wiring; now connect the ‘red’ of the fan to an outside arm of the rehostat. This is were I got confused – and it may be a good idea to test out your setup before you solder it in, to ensure you have the polarity right and your rehostat is working.

8. When all of the soldering is done and you’re satisfied, find a makeshift way to stabilize your fan in the position you’d like. Like I mentioned, I superglued it to an old spice container (which was also superglued to the bottom of the project box). Another note if you’re using superglue; give it a few hours to dry before you close up the box or you’ll get crusty junk coming out all of the openings of your device, yuck.

9. Use common sense/test runs, to align the magnets properly to spin the stir bar. Glue them down.

10. Clean up the inside of the box and when you’re sastisfied, screw up the box and enjoy!

Another quick note, if you’re in Chicago and want some help building one of these, drop me a line. I don’t mind :)

This entry was posted on Saturday, June 6th, 2009 at 10:57 am and is filed under equipment, musings. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.