Yeast Stir Plate

One item I've been planning on building for a while is a yeast stir plate. The purpose of the yeast stir plate is to boost the cell count in yeast starters resulting in higher pitch rates and healthier starters. This should reduce lag time before active fermentation begins and theoretically should improve the final product.

Commercial yeast stir plates can be fairly expensive so I'm going the DIY route. I wish I could claim I came up with the idea for the stir plate, but it's basically modeled after others on the web. The components and prices are as follows.

Disclaimer: I'm not an electrician and I can't guaranty the safety of this device. If you choose to build a similar device, do so at your own risk.

• (1) 80mm PC case fan - $2.49, Electronic Goldmine



• (2) Rare earth magnets - $2.00, Electronic Goldmine



• (1) 8x6x3 Project box - $6.99, Radio Shack



• (1) 25K Ohm 3 watt rheostat - $3.99, Radio Shack



• (1) Knob - $1.99, Radio Shack



• (1) Power supply - free



• (1) Switch - free



• Miscellaneous screws, zip ties, etc. - free



• Stir bar - approx $5 (yet to be purchased)

Here is a very basic wiring diagram that even non-technical people should be able to understand.

Click here for Steps 1-2

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Stir Plate - Step 1 - 2

I'm not going to go into a ton of detail because I figure most people that will attempt this project are somewhat technical and probably pretty handy. So here are the steps I used to build the stir plate:

1. I drilled a hole in the front of the project box for the rheostat. I also drilled a hole in the back for the power supply cord. Finally, I used a Dremel to cut out a relatively square-ish hole on the front for the power switch.

2. Next I connected the wiring...except for the fan. I didn't connect the fan at this point because it hadn't arrived yet. The connections on the rheostat are soldered, the switch uses female solderless terminals and I used a few crimp on connectors. I tried to keep things clean by using a few zip ties.

Click here for Steps 3-5

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Stir Plate - Steps 3 - 5

3. Next I mounted the fan. I chose to mount the fan to the bottom of the project box. A lot of the others I've seen have the fan mounted to the top of the project box but I wanted a cleaner look. Four #10 x 1.5 inch screws are inserted through the bottom of the box. A nut is tightened down on each screw on the inside of the box. Each screw is then screwed into the mounting holes on the fan frame. It seems pretty secure and I'll be able to adjust the height of the fan by a simple turn of the screws.

4. With the fan in place, the two wires are connected.

5. Next I attached the fender washer to the fan hub. I first tried mounting the washer using 5-minute epoxy and eyeballing the washer for center. This didn't work out very well because the washer was a little over 1/16th of an inch off center. Even on the lowest speed there was a lot of vibration. Luckily I was able to carefully scrape off the epoxy and gently pry the washer loose.

For the second attempt, I put a piece of masking tape on the fan hub, powered it on, then used a Sharpie to make several concentric circles. I then used a utility knife with the fan powered on to cut just outside the biggest circle so that the excess tape could be removed. I used the Sharpie circles as guides to ensure the washer was perfectly centered. I also used a hot glue gun to secure the washer rather than epoxy just in case it took more than one try. The second attempt was much more accurate and virtually eliminated vibration on all but the highest speeds.

Click here for Steps 6-7

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Stir Plate - Steps 6 - 7

6. The next thing I did was attach the magnets to the washer. I used the Sharpie to make a couple reference lines and temporarily taped them in place and tested for vibration. I then used hot glue to attach them to the washer.

7. The last step was just final assembly which consisted of attaching the box top, attaching a control knob to the rheostat, and finally adding a few silicone self-adhesive bumpers for feet.

Next up is ordering a stir bar and road testing the stir plate.

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Stainless Steel Ball Valves

I picked up some new ball valves off ebay. They're 1/2" Flowserve Series 4 all stainless steel ball valves and they are hefty. Each one weighs in at approximately 1.5 pounds and they're rated for up to 3000 PSI and 180 degrees Fahrenheit. I only paid $4.58 for both of them, pretty good deal. The 180 degree max temperature is a bit low so I won't be able to use them on my boil kettle, but they should work fine on the MT/LT, HLT, or conical fermenter.

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HERMS Design

I'm in the process of building a HERMS system. The brains of the system is the BCS-460 Programmable Logic Controller from Embedded Control Concepts. It will be composed of the basic elements present in other HERMS systems:

1. Hot Liquor Tank (HLT) - 5 gallon Rubbermaid cooler heated by a 1500 watt 120 volt water heater element
2. Heat Exchanger (HX) - 2 gallon Rubbermaid Cooler heated by a 1500 watt 120 volt water heater element and consisting of 10 feet of 1/2" copper tubing
3. Mash / Lauter Tun (MLT) - 10 gallon Rubbermaid cooler
4. Pump - Brand a model to be determined
5. Boil Kettle - 8 gallon

The controller will be used to turn the heating elements and pump on and off at various times throughout the brewing process.

Hot Liquor Tank >>

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HERMS Equipment - Hot Liquor Tank

The Hot Liquor Tank is based on a 5 gallon Rubbermaid cooler. The lid is drilled in the center and a temperature probe for the BCS-460 has been inserted. The HLT is heated by a 1500 watt 120 volt water heater element.

Heat Exchanger >>

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HERMS Equipment - Heat Exchanger

The Heat Exchanger is based on a 2 gallon Rubbermaid cooler. It holds approximately 1.5 gallons of water and is heated by a 1500 watt 120 volt water heater element. The heat exchange is accomplished with 10 feet of 1/2" copper tubing.

Mash Tun >>

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HERMS Equipment - Mash Tun

The Mash Tun is based on a 10 gallon Rubbermaid cooler. The lid is drilled and fitted with a grommet through which the return manifold is fitted. The return manifold is used for circulating the mash and for delivering the sparge water. It's contructed of 1/2" copper pipe and I've cut slots into the end of the T section in order to distribute the liquid without disturbing the grain bed.

1. System Startup >>

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1. System Startup

Controller turns on heating elements in Hot Liquor Tank and Heat Exchanger and heats water to preset temperatures. The water in the HLT will be transferred to the MLT and used for the mash in. Since the HEX is only 1.5 gallons and will not take very long to heat, it will probably be turned on after the strike water reached the target temp.
2. Mash >>

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2. Mash

The mash will be circulated by the pump. It will travel from MT to Pump to HX and back to MT. The HX will be used to maintain mash temperature for single infusion mashes and to increase temperature for step mashes and mash out. Sparge water will be heating in the HLT during the mashing process.

3. Sparge >>

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3. Sparge

During the sparge, hot water is pumped through the HX to the MT and the sweet runnings are collected from the MT in the BK. I may end up bypassing the HX, it just depends on whether I run into any problems with the HLT temps.

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