Self Stirring Mug Using Lego




I saw this self stirring mug on YouTube and then this friend introduced me to a piece of lab equipment called a magnetic stirrer. So I decided to create a little prototype of both using Lego pieces.


Step 1: What You Will Need

You will need the following pieces (Give or take)

Tape (Electrical works well)
2 Bar Magnets (or a lot of disc magnets)
(I used the surplus from

Lego Pieces: (if you decide to make it using Lego)
1 9V Motor
1 9V Battery Box
1 Lego Cable
1 6 x 8
2 6 x 10
4 1 x 2 (the ones which have the slots to hold a motor)
12 1 x 8
4 1 x 2
2 1 x 6
4 1 x 8
6 1 x 10
1 Crown Gear 24teeth
2 24 tooth gears
2 8 tooth gears
Some bushings and pins to connect it all

Step 2: Gear Train

The Lego motor spins at roughly 360 rpm which is quite slow so in order to speed this up we utilize a gear train. Below is a picture of the assembly. The end of the gear train is on the upper left and it will be the part that is attached to the spinning magnet bar.

Step 3: Build a Frame

You want to build a frame to support a cup so in this design I built it using Lego pieces. What is important though is that your frame is sturdy enough to hold a cup with liquid and has some clearance for the spinning magnet mechanism. I used a Lego connector that looks like a T shape to attach the magnet onto the gear train. I also used some tape to secure it. When the setup is complete you should be able to place the bar magnet on top and it will lock into place. I chose neodymium magnets because they were strong.

Step 4: Unresolved Issues

There aren't many steps to this because this was a short project and the video explains a lot of the details. If there were any parts that were unclear I would be glad to explain them or append to the instructable.

There were better ways to mix and blend but this one used magnets and Lego and was entertaining to watch. I didn't use this for drinking purposes due to some cleanliness issues but it sure did mix that iced tea well.

I used a plated magnet and to my knowledge it is plated in zinc. Not wanting to drink zinc I planned to cover the magnet in some form of non toxic plastic. In the past using some spray on liquid rubber to waterproof my use drive and I was hoping to find some similar to coat the magnets.

Also if anyone was planning to make this for drinking purposes I would recommend building a specialty cup that has the magnet fixed to the bottom so that it isn't a choke hazard.

Thank you and I hope you enjoyed this Instructable!



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    28 Discussions


    11 years ago on Introduction

    the metal bar is a magnet though, would there be any chemicals or particles that would mix with the liquid?

    3 replies

    Reply 10 years ago on Introduction

    You can buy the teflon coated-magnets without buying the whole stirrer. Here is a link to a place where they are pretty cheap:

    I actually prefer the ovoid (egg) shaped ones, as the bottom of my some of my mugs are not flat in the middle and the other stir bars don't spin as fast. Plus, they are small enough that they work in all sizes of cups.

    Teflon is non-reactive (for high acidity drinks like orange juice) as well as highly resistant to heat (coffee) although the magnet doesn't like the hot temperatures... But they are cheap enough and even with abuse they last for years and years.


    8 years ago on Introduction

    I might choke on the magnet, if I made a string and drilled a hole and attached it would it still work?


    9 years ago on Introduction

    Now I want to make one of these too :( There are too many good instructables that take up my day! :D


    10 years ago on Introduction

    ok. so as someone who owns a real hotplate / stirrer, i have one little detail everyone seems to be missing. that bottom magnet that is attached to the motor? Its not a bar magnet. Its a ring magnet. you want a ring that is about 3 inches outside diameter. epoxy it to a metal circle which you attach to a suitable motor. make sure it is centered or bad things will happen.


    10 years ago on Introduction

    I made this a day or two ago, great instructable! I didn't use exactly called for, but it worked. Problem is with making one of these it that you HAVE TO HAVE the perfect magnets. Most magnets I had were too weak or too bulky. Anther problem with making one is that the legos are hard to balance on a rod, even with adding a T-bar. and conmorse is right. Unless you get a magnet meant for this, magnet particles and possibly paint could get in it. Fun, but impractical.


    10 years ago on Step 3

    i am confused on how to atach the magnets to the motor assmbley

    2 replies

    Reply 10 years ago on Step 3

    I have a T shaped Lego piece attached to the motor shaft. I taped a strong bar magnet to that piece. Its shown in the second and third picture of step 3. Then the red plate is placed over and a freely moving magnet is placed on top. The magnetic attraction of the bottom magnet causes the top one to spin.


    Reply 11 years ago on Introduction

    Yes, the only thing that the thing in the cup is is a metal bar, just make sure it is clean


    11 years ago on Introduction

    To prevent someone from swallowing the stir rod take a disc shaped magnet and hold it to the bottom of the cup. The indentation that is likely in the cup will hide the magnet, and both magnets should stick in place. If the stir rod isn't a strong enough magnet to hold the second magnet to the bottom of the cup, then use the second magnet to drag the stir rod out of the cup before drinking.

    1 reply

    Reply 11 years ago on Introduction

    erm a MUCH easier and better one to do would be simply have an inversed "T" where the "-" part is the magnet and the "|" part is a large piece of metal/plastic, if the magnet is plastic coated so it is non-toxic and the attachment doesnt use toxic chemicals then it should still be drinkable, as the handle is vertically attached (perpendicular) it will be in the centre of the vortex created by the magnet and so will not creating any detrimental effect to its speed and being easy to remove. This also leads to a possibility of making it with larger bottles as you could add fins to the handle to create flow.