Comments on: A Stirring Hack

By: BBCOR Approved Bats

BBCOR Approved Bats — Wed, 15 Jun 2011 17:57:50 +0000

Fine article. Theres a lot of good info here, though I did want to let you know something – I am running Mac OS X with the latest beta of Firefox, and the layout of your blog is kind of flaky for me. I can read the articles, but the navigation doesnt function so good.

By: XBox Hacker

XBox Hacker — Sat, 09 Jan 2010 17:29:44 +0000

I agree with teflon coating.

By: normaldotcom

normaldotcom — Fri, 09 Oct 2009 21:52:06 +0000

I made one of these a few months back, with a PWM’ed high-speed muffin fan, some hard drive magnets, a H-bridge, and an avr… it actually worked quite well.

By: coo no L blades

coo no L blades — Fri, 09 Oct 2009 19:54:33 +0000

Hehe, nope mine isn’t used in corrosive liquids. But I’m sure you’ll figure out a way to beat that.

It still seems like the main issue is the magnet decoupling with the motor. If that’s the main issue making your motor slow down won’t make it stir any harder.

I think your application would be cool for a magnetically coupled rotor in an underwater vehicle. In fact hurry and wrap this up so I can “borrow” your design. j/k

By: Carlos

Carlos — Fri, 09 Oct 2009 17:42:43 +0000

Make a search at the Google Patents about stirring plate or Stir Plate to avoid problems.

http://www.google.com/patents

By: liam

liam — Fri, 09 Oct 2009 16:18:23 +0000

I’d write a simple PID controller to run a power resistor/thermocouple and get sophisticated temperature control. Throw a peltier in there too and get very flexible control.

By: Vaevictus

Vaevictus — Fri, 09 Oct 2009 15:35:59 +0000

Easy. Best use for a stirrer: for a yeast starter for brewing beer.

By: ClutchDude

ClutchDude — Fri, 09 Oct 2009 13:35:31 +0000

While a simply LM317 could adjust the speed, I too think it’d be neat to rig all sorts of sensors into the Arudino, possibly an array of stirplates for automated…um…mixing and heating?

THEN use it to give out status updates so you could be comfortably sitting in your office, monitoring it rather than the lab, as BuudhaFW stated.

It’d be real neat to measure turbidity(?) and temperature and adjusts based on a profile. (I can think of yeast starters benefiting from this a lot!)

@eutatic

The stirplate can be sealed to keep any vapors from entering. After all, it’s only be used to spin a magnetic field.

By: Eutactic

Eutactic — Fri, 09 Oct 2009 12:23:30 +0000

I hope that fan (and to an extent the whole project) is non-sparking if this stirrer is going to be used with flammable solvents.

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By: jproach

jproach — Fri, 09 Oct 2009 06:01:03 +0000

Teflon (PTFE) stir bars are cheap enough on ebay that I wouldn’t bother trying to hack something as a replacement IMO.

Great otherwise though.

By: BuudhaFW

BuudhaFW — Fri, 09 Oct 2009 03:31:31 +0000

And you should use teflon to coat your stir bars, easier to clean, longer lasting and stable in almost anything.

By: BuudhaFW

BuudhaFW — Fri, 09 Oct 2009 03:30:19 +0000

Wow never really thought of bringing arduino into the lab. The above mentioned functions would be great if one could simply enter parameters, and have the device shut off if it drifts out… perhaps I could monitor multiple experiments from the office (better air, less ether and I could drink coffee). Hmmmm I like this.

By: Rachel

Rachel — Fri, 09 Oct 2009 02:58:43 +0000

It’s more efficient because it doesn’t need to turn the relatively massive motor spindle, and lose energy from its bearings. And with no moving parts, it’s much more durable and longer lasting. It can be made very thin too.

Aside from the electromagnet design, it should be fairly easy to male. Simply rectify the AC line current, and pulse it through the coils with some big MOSFETs.

As for making stirring bars, few materials other than glass or teflon will stand up to harsh chemicals. I once tried sealing a neodymium bar magnet in glass tubing, but I foolishly neglected the Curie point of the magnet and ended up with a useless glass lump.

By: wdfowty

wdfowty — Fri, 09 Oct 2009 02:32:11 +0000

Munden beat me to it. Lol just about the only thing twitter is good for.