So what is a stir plate and why is it useful?

Well, as its name implies, a stir plate is a piece of equipment that continually stirs liquid by means of a magnetic stirring bar. There are a variety of practical applications for homebrewers, cocktail geeks, and home cooking. Let’s look at how to build one, and I’ll talk about some practical applications later.

First you will need to source your parts. Most of these can be obtained for free, if not, you can probably purchase everything for around $30. Here is what you will need:

  • Cell phone charger or any DC power supply in the 5-12 volt range.
  • Computer fan. Can be obtained from old computers or electronics stores.
  • Magnets – These can be obtained easily from old hard drives, although they can also be purchased cheap from craft stores.
  • Wire – About a foot of 18-20 gauge wire is needed.
  • Hardware – 10/32 nuts and bolts. Any hardware store will have these.
  • Switches – 12 Volt DC/30Amp Rocker Switch & 25 ohm 3 watt Potentiometer.
  • Project box – Any box or enclosure can be used as long as it fits your components and is not magnetic.

Now that you have your parts, let’s get this baby up and running.

The first step is to mount your fan into your enclosure. I mounted mine into a wooden box using 10/32 bolts. Locknuts are used on the bottom of the box and double up as feet. Regular nuts are used on the inside of the box to place the fan towards the top of the box. Once you have the fan positioned, mount your power switch and Potentiometer in your box and you are ready for some wiring!

The first step is to strip the ends of the wires coming from your power supply and your fan. Everything can be soldered, but I used some spade connectors so I wouldn’t melt my plastic switch. Before soldering any wires together, make sure that your power supply wires are fed into your box 😉

Take the Black wire from both the fan and your power supply and connect these two wires to the “Earth” connection on your switch. Then connect the Red/Black&White wire from your power supply and connect it to the “Supply connection on your switch. Then, using the scrap wire, attach the center pin of the potentiometer to the “Load” connection of your switch. Last but not least, attach the Red wire from your fan to the right pin on the potentiometer. Now plug in your power supply, turn on the switch, and your fan should spin. Turning the potentiometer should slow/speed up the fan. If so, you are nearly there. At this point, I was concerned about airflow to the fan, so I drilled 3 holes in the back of my box to prevent overheating.

The last thing to do before closing up the box is to position the magnet onto the fan. Turn your potentiometer all the way down so the fan spins its slowest, and place the magnet onto the fan. The idea is to get the magnet centered so that the stir bar will spin easily and freely. Once you see that it is centered, glue the magnet down to prevent it from being knocked or drawn off center, close up the box, and you are good to go. You can test your new stir plate out by placing a bar magnet, stir bar, or bolt into a flat bottomed glass container filled with water. Center it on the stir plate and let it rip! Come back soon for some practical applications to apply to your new toy. Cheers!