How to Make a Magnetic Stirrer That Doesn't Cost Like a Professional One





Introduction: How to Make a Magnetic Stirrer That Doesn't Cost Like a Professional One

About: I enjoy making things by myself, trying to make this world better.

I needed a magnetic stirrer for my chemistry lab so I made a cheap one that looks almost like a professional one, but doesn't cost very much.
It is made from recycled parts from an old CD-ROM, a printer motor and things from an old CRT screen board (like resistor).
       The things you need:
   - a CD-ROM metalic case (or what case you want)
   - a piece of aluminium sheet
   - 10 screws (3 mm diameter)
   - 6 screw nuts (for 3 mm screws)
   - 2 circular magnets (1 cm thick, 1-1.3 cm diameter)
   - a 5.5 cm circular aluminium sheet
   - a little passive heatsink (optional)
   - a printer motor (almost any motor could be used )
   - 1 little screw for motor
   - a LM317 chip
   - one 0.1 uF capacitor
   - one 10 uF capacitor
   - one 5K potentiometer
   - one 240 ohm resistor
   - a universal board for electronics (4 cm width x 2 cm lenght)
   - a 12 V AC power supply
    -a knob

Step 1: Step 1

Let's begin!!!
Firstly let's drill some holes.
Drill the small holes with a 3mm drill bit, the big one I drill with a 10 mm drill bit and the smallest with 2.5 mm drill bit.

Images have indications about lenght and width, so don't miss them,

Step 2: Step 2

Let's make the circuit.
When the circuit it's done, bend down the potentiometer.

Step 3: Step 3

Here are the magnets and their support.
Drill through the center of circular aluminium sheet.
I used a plastic support for more stability.

Step 4: Step 4 - Assembling

Step 5: Step 5

And there is it. It's done and assembled.
Hope this tutorial was useful for you.
You can use it for stir almost everything.
As stirring bar you can use a magnetic bar from CD-ROM or you can buy a coated one that not reacts with other materials, even neither with acids.

Step 6: The Magnet and the Power

I make my own stirring magnet covering a little magnet with hot glue.
In other photos, you can see the power.

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    Interesting project

    Interesting. I have used a very similar circuit to drive a laser diode, also scavenged from a CD/DVD burner.

    2 replies

    A note to others who read this: this circuit should not be used to drive a bare laser diode! Laser diodes are current controlled devices that are non-linear and this circuit is a voltage regulator. In other words, it is near impossible to drive a laser diode with only this circuit without risking blowing it up (laser diode current shoots up to insane amounts with a very small change in voltage). If you want to use this circuit, be sure to add a current limiting resistor like you do for LEDs, otherwise I suggest another circuit that is current regulating (have a look at Dan's high power LED driver instructables for dirt simple and cheap ones).

    Some here might reply that it worked for them, well good for them. They most likely used a laser diode module that has current regulation integrated (some look just like a plain laser diode). I dont know if the diodes in CD/DVD burners are usually packed in a module or not.

    you can actually use the lm317 as a constant current generator by using a slightly different circuit

    surely you mean a 12 volt DC power supply, not AC

    i am not being a downer, but, that magnet rotating under the aluminium plate produces eddy currents, and thus puts off a lot energy as heat i suppose... (much like an induction cooker).. if u substitute the aluminium plate with something else, it would be much more efficient...

    1 reply

    It is just a prototype. I mean it was. You can see in my projects the 2S magnetic stirrer.

    Very nice - I've been wanting one of these for ages. However, for maximum use, you need to build one with a thermostatically controlled hot plate as well!

    1 reply

    If you tell me how to make the hot plate, I'll do it.

    How would it work for mixing epoxies or small amounts of hardening liquids ? it looks good and the "Ible" quite good !

    10 replies

    Use some thick wire, bend it into a 'T' shape, chuck it into a power drill. Cheap, disposable, high-torque mixer for thick fluids. I use it to mix epoxies and silicones.

    Thanks i welded a small one together for that i was wanting something to mix without creating to many bubbles in the clear or colored resin i thought maybe a stronger magnet would do the trick with a variable speed motor and a snake egg magnet might work i still maytry it just to experiment with it

    Thanks again

    Are you trying to mix *both* components of epoxy together or adding , say, a color to one? People call many different things "epoxy", so I guess we'd need to be clear. If you're mixing color, I can see why you would need a mixer like this magnetic one or simpler ones that were offered here but if you are mixing the epoxy with the hardener, they don't need that kind of thorough mixing - they are combining at the molecular level and they are not mixing in the general sense. In other words, no reason to mechanically "mix" them together as such - all you need usually is a couple of stirs with a disposable wooden stick and the hardening process starts by itself (talking about liquid epoxy resins - more viscous epoxies may need more help in bringing components together but still nothing so thorough as a high-speed mechanic mixer ).

    As far as bubbles, magnetic mixing does not preclude bubbles - if you spin fast enough, there will be a vortex and it'll create plenty of bubbles. You need to either vacuum your resin if it's a longer hardening one (20+ min) or exact opposite - cast under 60-70psi pressure if it's a fast curing one to simply suppress the bubbles and keep them very small.

    If you're going for a completely crystal clear bubble-free transparent look, using a long-curing resin and vacuuming it while it's hardening is the only way to achieve this that I know of.

    Yes, you DO need thorough mechanical mixing. You want a homogeneous mixture of the epoxy, catalyst, and crosslinker molecules in order to build chain length and maximize structural integrity. It varies between manufacturers and recipes , but typically, Part A contains expoxy resin (Bisphenol A diglycidyl ether) and a short chain polyurethane polymer, and Part B contains polyfunctionalized amines/thiols (crosslinkers), functionalized polyamide resin, and expoxy catalyst. The epoxy needs to "run into" the crosslinker and the polymer molecules in order to react with them, and you can't get that unless you have thorough mechanical mixing. If you partially mix (and end up with "swirls") instead of fully mixing, what happens is you get polymerization at the interfaces (i.e. curing), which prevents further molecular migration. So what you are left is uncured Part A (a liquid) and uncured Part B (a liquid), trapped in a matrix of solidified resin. I've worked a lot with Bondo and I get this all the time if I portion my catalyst wrong, it ends up more rubbery than solid. While it may feel solidified, its structural integrity will only be a fraction of that if you mixed to homogeneity, or as close as you can get. Always mix 2-part systems thoroughly.

    I mix clear casting resins for some things and add colors as well i mix a-lot of small amounts of fiberglass resins i now i could never mix gelcoat with it they are way to thick but it would be nice to have the resin for fiberglass already spinning before i dropped in the catylists it would cut down on the expense of stir utensils for one thing sometimes i use resin for a sealer on wood thats going to be exposed to water i've done several outside tables with straight resin with no fiberglass and they have been outside for years with no problems but not having to deal with air bubbles would be a treat .....

    Every epoxy that I have ever used is too viscous for a magnetic stirrer. They excel at things like blending flour or cornstarch with water for cooking.

    though I know for sure that Araldite goes VERY runny when you warm it up - but the setting time seems to reduce in some sort of proportion to the temperature.

    I don't try mixing hardening liquids, but I think at maximum speed it can mix epoxies too.
    Make a magnetic stirrer, try mixing hardening liquids and then tell me if it can't mix or not.
    I think it can work without 12 V AC power supply too, so the speed will increase and also the power.

    it wouldnt work very well for hardening liquids.

    one, they are very viscious liquids, and would never achieve enough speed to thoroughly mix the two parts.

    and two, you'd need to be sure to remove the stirrer fairly quick, otherwise it'll glue it to the cup.

    Did you try to mix epoxies with it ?