DIY Stir Plate

Hello Brewers,

Time for an equipment upgrade!!! In this post I'll be writing down basic instructions to make a DIY Stir Plate at a very affordable price. The equipment used in this project are sourced locally.
Starting with the basics. Why do I need a Stir Plate?

Many homebrewers under-pitch yeast (unintentionally) by using old, partially viable yeast that is very near or way past the expiry date. A stir plate helps you culture higher cell counts of good, healthy yeast for quick fermentation, lower risk of infection creeping in and off-course, better tasting beer. All this takes lesser time (12-18 hours) than a regular yeast starter (3-4 days). Stirred starters are continuously aerated with oxygen which is vital for yeast propagation and health. Stirring diffuses out carbon dioxide, a by-product, which inhibits yeast growth. It also keeps the yeast suspended and in constant contact with the nutrients thereby giving you healthy strains of yeast. You also save on yeast packets if you harvest your yeast from previous batches. This in-turn gives you a lowered cost on ingredients per batch.
"You can actually make a starter for 20L batch using the yeast sediment from just a pint bottle of your homebrew." How cool is that !!
video

Coming to the real deal. The Build

I have managed to build the Stir plate within ₹600. I have mentioned the estimated price of materials required in [ ]. There are various grades and quality of the material that can be used. I personally used mid range articles. I urge you to scavenge your house for items listed below, this will only make it cheaper.

Besides this you will also have to buy a borosilicate conical flask [₹250-600 depends on volume it can hold] and a magnetic stirrer bar [₹200-300]

Material:
  • 1 Project box / Empty container / Wooden box [₹0-200]
  • 4 Long screws, 4-8 nuts and 8-16 washers [₹20-40]
  • Wire and 1 plug [₹40]
  • 1 DC cooling fan (generally 12V) [₹90-200]
  • 1 AC to DC converter (12V 1A) [₹200-400]
  • 2 Rare earth magnets [₹80-150]
  • Fevikwik [₹5]


Tools:
  • Screw driver
  • Wire stripper
  • File/knife
  • Drill machine


  1. Ready your project box. Place the DC cooling fan over the it and mark out the approx locations for holes to be drilled. 
  2. Drill the holes and insert 4 long screws along with washers and check the alignment of fan and screws.
  3. Ready your electrical tools. Connect one end of the wire to the plug. Other end of the wire will be connected to the AC end of your AC to DC converter.
  4. DC end of the converter will be connected to the DC fan. You can securely place this converter inside of the box to make it more compact. You will have to drill a hole to let the wires in.
  5. Draw a line in the center of your DC fan and use fevikwik to stick the rare earth magnets on the spinning side.
  6. Position the fan with magnets facing inside of your project box.
  7. Recheck your electrical connections. Tighten all screws.
  8. Fire it up and check for contact between fan blades and the project box. Adjust the height of magnets from position box using washers/screws.
  9. Your DIY stir plate is now ready for use

For a test run, fill the flask with water, slide in the magnetic stirrer, place the flask on your Stir Plate and switch it on. You should have a whirlpool like in the above video.

All in all, your stir plate along with flask and stirrer will cost your around ₹1000

Comment in the section below if you have any doubts/queries.

Cheers till next time!

12 comments:

  1. Replies
    1. Rare earth magnets are available on ebay and amazon, example - http://www.ebay.in/itm/Strong-Rare-Earth-Neodymium-Magnets-10Pcs-10mm-Square-/181723784559?hash=item2a4f94e56f

      OR

      http://www.ebay.in/itm/10pcs-of-12mmx-1-5mm-Rare-earth-NdfeB-neodymium-strong-magnets-N52-Free-Shipping-/131624539668?hash=item1ea56f1614

      You just need 4 pieces, 2 on each side.

      Delete
    2. Something like this -

      http://www.amazon.in/MFM-Neodymium-Magnets-NdFeB-10x10x2/dp/B00VD0NKZS/ref=sr_1_11?ie=UTF8&qid=1444642274&sr=8-11&keywords=neodymium+magnets

      Delete
    3. Hi, yes, above links are exactly the magnets you need. The ones Sapan and I use are a bit stronger because they have a pull force of about 3lbs.

      Any neodymium magnet with a minimum pull force of 1.5lbs will work fine.

      If you are unsure about the rating, buy any button magnet with N40 or N42 specification.

      Delete
  2. Hi, any specification, essentially the material, for the magnetic stirrer or the stirrer magnet.. and where to get it from.

    ReplyDelete
    Replies
    1. We have used a 3cm - 3.5 cm stir bar and it works fine. Most of these are teflon coated and inert to chemicals.
      It looks like this - http://www.snapdeal.com/product/techtone-magnetic-stirrer-bar-35mm/1574501774

      Most lab supplies shops in the city have it, since its a very common lab item.
      Try to convince them to give you a single piece.

      Delete
    2. Few more on Amazon - http://www.amazon.in/Techtone-Magnetic-Stirrer-Bar-28mm/dp/B00R95B2AQ/ref=pd_sim_sbs_201_1?ie=UTF8&dpID=41jBIQBaOaL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=13JS1DZS7MDYP8VP4NGM

      Delete
    3. Hi, Arup

      As Sapan mentioned 3-3.5 cm stir bars are exactly what you need. The real test is getting your magnets positioned properly. The stir bars should be within the magnetic field so that it doesn't get thrown off while spinning.

      Also there are different types of stir bars. What you need is the one with a ring in the middle. This helps to reduce the contact surface between the flask base and the stir bar that will help it spin more freely.

      I suggest you do some research on various lab/chemical suppliers in your area, they will most definitely have it.

      Delete
    4. Hi, thanks for your suggestion, I have got the right one (3 cm) from a lab shop in Kolkata. What I require is a sketch of how the rare earth magnets are to be fixed on the DC cooling fan.... if any polarity to keep in mind while fixing, and how far apart they need to be places, etc.

      Delete
    5. Hi Arup,

      Check this video where they show how the rare earth magnets are fixed. - https://www.youtube.com/watch?v=XVLB9c0j1iU

      Delete
    6. Have seen the video... thanks... will make one now.

      Delete
  3. These plates are really helpful in the testing and to get accurate results. Now these days magnetic stirrer hot plate are very reliable for the testing in laboratories. Its advance features like easily adjustable up to 250°C and reaches its maximum temperature within a second. The magnetic stirrer that is fitted in this device is adjustable from 0 to 1400 rpm.

    ReplyDelete

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