I know there are about a million websites out there showing you how to make a DIY stirplate but I thought this might be worth posting because I have not seen one quite like the one I came up with wholly by accident. Before I get to it, you can stop reading if you are looking to make a variable speed stirplate because this one is very simple one without the variable speed option. That said, I don’t really think you need it but that’s just my opinion. This project is super easy and will save you at least $40 compared to buying a premade one which is not much more different than this.
As I said above, this turned out to be a totally by accident stirplate because I already had the fan that ended up fitting just perfectly to the project box I bought from amazon. This stirplate should take you all about 10 minutes to put together because unlike others I saw online, this one happens to fit perfectly.
120mm computer fan – now I am not including this on the price list because I had already bought a box of these for a kegarator and son of fermentation fermentation chamber. That said, you should be able to pick one of these up for under $10. You could use a smaller fan but it won’t be nearly as easy to put together with the specified project box.
Rare earth magnets – I bought some tiny rare earth magnets from ebay for about $6 but you can easily use a computer hard drive magnet. Make sure you don’t get super thick magnets because the project box top will not fit on top of the fan without spacers. The magnets I got were about 2-3mm in diameter x 1mm in thickness, in hind sight, slightly bigger ones would have been better because I had to stack two magnets on top of each other for a total of 4 (2 per side).
120mm Project box– I think this is the key to this project because the 120mm fan fits this project box PERFECTLY. Absolutely no need to drill holes, line stuff or anything. The fan fits the box like a glove. You just need the right diameter and length screws to sandwich the fan in between the project box and project box top. $7
Magnetic stir bar – I went with a 1″ stir bar. You can do a little bigger but I think 1″ is about the smallest you can go. $6
Power supply – If you’re like me, then you probably have a pile of these laying around so I didn’t add this to the project cost. I had a 12v power supply lying around that worked well for my purposes.
Screws – You will need screws that are skinny enough to fit through the fan holes and be long enough to reach the project box holes. I think about 1 1/4″ or so screws will work. Take your project box to home depot or whatever to make sure you have the right screws.
Building this should be super easy and will probably take you less than 10 minutes. You will need super glue or hot glue gun, a screw driver, a drill and either electrical tape or sauter to connect the wires.
First step is to glue the magnets to the fan center. Easiest way to do this is to put the magnets on the stir bar to get the proper alignment because you have to get the magnet poles properly for this to work. After that, either super glue or hot glue the magnets to the fan center.
Once you have that glued on, cut whatever end is on your power supply and connect it to your fan. Again, this one is not using a variable speed controller. Also, make sure you put a knot on the power supply on the inside of the project box so that you don’t accidentally pull the cord and disconnect the wires. I sautered mine and used shrink tubing to protect the connections. Of course you will need to drill a hole on the project box big enough to fit the wire.
Now it’s just a matter of sandwiching the fan in between the project box and the project box top.
That’s all there is to it now just plug it in with a glass container on top with the stir bar to test.
My power supply is not particularly strong so I don’t get a huge vortex when the flask is filled to capacity but it stirs the yeast more than enough. You don’t need a huge vortex, you just need the yeast to stir and this does a great job. Feel free to add a speed controller and larger power supply if you need it. I only make 1L starters for my small batches so this is perfect for me.