Sciencemadness Discussion Board

DIY magnetic stirrer

felis - 6-10-2009 at 13:04

Gentlemen,

I recently built a magnetic stirrer mostly from junk which works surprisingly well. Project details and pictures here:
Part 1.
Part 2.

Enjoy,

/felis

stateofhack - 6-10-2009 at 14:25

Thanks, much of use :D

MJ_ - 6-10-2009 at 23:01

Nice work!

Reminds me of one I made once from a PC fan, magnet and a potentiometer. Was suprised at how well it worked considering how crude it was.

Bobross - 7-10-2009 at 05:42

Excellent! I'm currently working on a stirrer hotplate, also using an Arduino. I don't think it'll end up being much cheaper than buying a second hand one once I factor in buying the Arduino board, but I'll be able to use the controller for other projects too. That code you've posted should come in handy, I'll post a report when it's finished.
I think I'm going to add an LCD display to show the heating and stirring levels, maybe I'll add a temperature control as well.
Thanks for posting.

[Edited on 7-10-2009 by Jhonbus]

grndpndr - 5-11-2009 at 23:03

FUBAR,Sorry,grndpndr

[Edited on 6-11-2009 by grndpndr]

kmno4 - 6-11-2009 at 04:12

Topic with the same title exists for a long time:
http://www.sciencemadness.org/talk/viewthread.php?tid=3056

1281371269 - 6-11-2009 at 06:20

I just can't get mine to work. I purchased a 40mm diameter neodymium magnet for it, built a case, spliced a phone charger as the power supply, but it just doesn't work and I have no idea why. With a proper teflon stir bar it doesn't work at all and with nails it sometimes works for a bit then stops. Is the magnet not strong enough? It's the strongest one I've ever encountered!

felis - 11-11-2009 at 22:31

What exactly stops working? The motor stops spinning? This means your power supply is not strong enough - get a bigger one.

watson.fawkes - 12-11-2009 at 07:36

Quote: Originally posted by Mossydie  
I purchased a 40mm diameter neodymium magnet for it
Which way is the disk magnetized? Is it North on obverse and South of reverse, as is typical? Now, what's the net torque on a metal bar lying right above the surface of such a spinning disk?

1281371269 - 12-11-2009 at 14:15

Nope it was a half south half north. The motor keeps spinning, the bar doesn't move or spins madly for a bit then stops.

felis - 12-11-2009 at 19:39

You need a pair of magnets glued to a motor with opposite poles facing up.

Sedit - 12-11-2009 at 20:22

Quote: Originally posted by Mossydie  
I just can't get mine to work. I purchased a 40mm diameter neodymium magnet for it, built a case, spliced a phone charger as the power supply, but it just doesn't work and I have no idea why. With a proper teflon stir bar it doesn't work at all and with nails it sometimes works for a bit then stops. Is the magnet not strong enough? It's the strongest one I've ever encountered!



Slow down the motor quite a bit and see if it couples with the stir bar. I find with the homemade ones of mine that if the magnet underneath spins to quickly the stirbar will now keep up correctly yet when I slow it down(used my finger for a break pretty much) it would grab the stirbar and spin correctly. After that it would pick up and run full speed but sooner or later loose its couple again and just slowly spin. Try running it slower and see if its the same as the problem I was having.

1281371269 - 13-11-2009 at 06:33

I've tried that, it's actually running pretty slowly so it's unlikely that this is the issue. The best bet is probably to try what felis said - I'll give it a go and if it still throws up problems I'll just buy a proper one.

Thanks for all the advice :).