Picture of 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

Picture of 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 www.kjmagnetics.com)

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
knex_mepalm5 years ago
I might choke on the magnet, if I made a string and drilled a hole and attached it would it still work?
Kaiven6 years ago
Now I want to make one of these too :( There are too many good instructables that take up my day! :D
freezier6 years ago
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.
Speedmite6 years ago
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.
conmorse7 years ago
the metal bar is a magnet though, would there be any chemicals or particles that would mix with the liquid?
cooblades (author)  conmorse7 years ago
The metal bar in the video is a magnet. You would have to coat the magnet with a non reactive plastic, or buy it already covered. Chem suppliers have them. Normal magnetic stirrers are hundreds of dollars. Here is a site that offers some examples of what I'm talking about.
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.
wotot27 years ago
i am confused on how to atach the magnets to the motor assmbley
cooblades (author)  wotot27 years ago
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.
you made me want to get my legos out again :( and I have no place to put them.
nicolasjara7 years ago
I like it.
conmorse7 years ago
Would it still be safe to drink the water?
Yes, the only thing that the thing in the cup is is a metal bar, just make sure it is clean
Yueh167 years ago
That is really smart.
VincentVX737 years ago
I've been thinking about building my own magnetic stirring device for a while now, but I must admit using legos never occurred to me...thanks for the time saving idea! Oh, and good choice on the music, Paul Van Dyk is simply mesmerizing.
Negafen8 years ago
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.
thinker Negafen8 years ago
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.
Negafen thinker8 years ago
Umm... read my post again, I'm not talking about anythnig that goes in the cup, or gets attached to the bottom. Just something that you can sit there as a quick fix for a mentioned problem in the instructable. I'm talking about after, so your guest doesn't accidentally swallow the rod. Also, it's not my instructable, and I didn't mention the stirring portions of the instructable at all. Also also, adding fins will not help in the slightest. The high rpm is what creates the vortex, add fins and you'll add too much resistance. You'll encounter something known as "spin out" which is when the magnetic coupling is not as strong as the hydraulic resistance, meaning your finned T thing will lethargically lurch around in the cup. Stick with the sciences and you'll encounter actual high speed electronic stirrers, you'll see a total lack of fins on them.
cooblades (author)  Negafen8 years ago
I hate to take sides, but negafen is right about spin out. I maxed out my device at around 3000 rpm. The vortex is amazing, it reaches the bottom completely as you could see in the video. It mixed 3 tablespoons of ice tea mix in a few seconds (not that I'm going to drink it). I gave the inversed T idea a shot and the bar is very unstable, sorry thinker :-(. The fins approach I'm not even going to try because at 3000 rpm I know I would lose coupling.
ahh reet no problemo, when i posted that i wasnt sure whether it would create drag on it or not but now i think about it it does make sense >_< and yeah, i get what you mean about the bar being unstable after i tried my own idea. thanks for readin it tho,
lemonie8 years ago
This is really cool. I've spend so much time using expensive Ika stirrers...


ewilhelm8 years ago
Nice use of stop-action on the lego build part!
josh921768 years ago
There was also another version published by g0pher, didn't use lego though ;-)
cooblades (author)  josh921768 years ago
cool I will take a looksie
This is really neat, i think I'm going to make this tomorrow, Thanks alot for sharing :D