DIY magnetic stirrer

I just finished my homemade stirrer, I used:

1. DC motor from old inkjet printer
2. Magnet from broken 3.5" Hard Drive
3. Spare AC to DC 5V/2A adapter from a PSP
4. Wood and Plastic Sheet for the casing

It was pretty easy once I figured out how to adapt the magnet to the motor, first I used some rubber bands connected to a ball bearing where the magnet was going to fit but finally I just simply glued the magnet to the motor and it fitted quite nice and is also balanced.

The motor and magnets were free, the adapter and casing costed about $5 combined.

First picture shows all parts (red layer is water with colorant and clear layer is mineral oil).
Second picture is a macro of the motor attached to the base.
Third picture shows the stirrer working (you can no longer see the two layers).
Fourth Picture is a macro to the "whirlwind" (I don't know the proper word in english) which is barely visible btw.












[Edited on 6-12-2010 by puppycock]

Quote: Originally posted by puppycock

Fourth Picture is a macro to the "whirlwind" (I don't know the proper word in english) which is barely visible btw.

Quote: Originally posted by Gearhead_Shem_Tov

Variacs are usually autotransformers; they don't have two windings, primary and secondary, rather they have one winding used sorta like a potentiometer voltage divider. This means they don't provide galvanic isolation between input and output. As long as what you think are Hot and Neutral on your AC input lines really are, then you're OK. If they are reversed, though, you could have the lethal situation of having Hot connected to what should nominally be at AC ground potential. Since this is often connected to a metal chassis, the first time you touch both the chassis and a true ground will unfortunately also be your last time. -Bobby

My magstirrer.
LM317 as a speed controller and a hdd magnet glued on a 92mm casefan.

Simple cheap and good enough.

Here's a gallery with more indepth and build pix.
http://img72.imageshack.us/gal.php?g=img8351c.jpg

Quote: Originally posted by Stasis

Quote: Originally posted by Gearhead_Shem_Tov   ... As long as what you think are Hot and Neutral on your AC input lines really are, then you're OK. If they are reversed, though, you could have the lethal situation of having Hot connected to what should nominally be at AC ground potential. Since this is often connected to a metal chassis, the first time you touch both the chassis and a true ground will unfortunately also be your last time. -Bobby Ah ok, thanks for the info. Live and Neutral are always the same sides, but in saying that, it's hardly something I'd be willing to mess around with..

Stator and back-EMF

I made a while ago (all the process wasted only about 1 hour) a improvised magnetic stirrer to make some experiments with mead (fermented honey)..

Two same HD magnets were glued on a mild steel disk and this on a ordinary 12V PC cooler:






Some small wood pieces were glued in the way seen in picture to form a little gap between rotating magnet and upper surface in which the container with stirr bar will rest.
The steel disk was necessary to shield the cooler against the magnetic field of the magnets. Without it the cooler just dont spin.
Detail:




A cheap plastic bowl was used as this 'upper surface':




glued:


and this was glued above an old ATX PC power supply (with most of it wires removed). I forgot to took photos of that step, but doesnt matter as it will be evident below.

Next, the stirr bar.

Looking my box with an assortment of electronic components (most of it scavenged from scrap), I found an interesting small inductor:




removed the copper wire:




Then sanded the soft ferrite rod and washed it in hot acetone (to remove glue traces), then water, then dried it.
Next step was tight winding PTFE tape on it.




The result:



The whole thing at work:





Video I made from operation:

<iframe sandbox width="420" height="315" src="http://www.youtube.com/embed/noIIbJhec_E" frameborder="0" allowfullscreen></iframe>

[Edited on 17-10-2011 by Aqua_Fortis_100%]

Thanks Nicodem, actually this is so obvious that I didnt noticed. =)

Anyway, this is not to be a problem tought, since like I said, I will use it to make mead (to stirr yeast in a closed system and make something better suited to get me and my several girlfriends drunk ).

My plan to make a stirrer ideal to chemistry hobby includes a heating unit too, like 'professional' units. So the tip you gave about motor will be useful and I will use that in future, thanks!

Quote: Originally posted by gatosgr

Why not use the circuit of a bldc motor and just rewind the coils or use a ferrite material shaped to redirect the magnetic flux at the top where the stir bar would be? [Edited on 6-6-2016 by gatosgr]