Another DIY stir plate

[Mattrox]

I ordered this today.

http://www.amazon.com/gp/aw/d/B00080G0BK/ref=mp_s_a_1_1?qid=1447320054&sr=8-1&pi=SX200_QL40&keywords=thermaltake+usb+fan&dpPl=1&dpID=51qK1C-adTL&ref=plSrch

USB fan with a speed control knob built in. Saves some work, can be powered from my phone charger, works for the USA crowd.

Was about to get some magnets from eBay. Will 10mm x1mm discs work?

 

[roastinrich]

I found to 10 x 1mm more likely to throw the bar. I used the 10x 5mm but you could always super glue a few 1mm together if the force is not with you.

 

[Mattrox]

Thanks. I got 8mm x 5mm discs.

I'll play with positioning before I glue them in place.

 

[Mattrox]

I got my USB fan from amazon today. It's easy to take apart. Here is the result.



Only needs a few parts to turn it into a stir plate.

 

[vortex]

I ordered this today.

http://www.amazon.com/gp/aw/d/B00080G0BK/ref=mp_s_a_1_1?qid=1447320054&sr=8-1&pi=SX200_QL40&keywords=thermaltake+usb+fan&dpPl=1&dpID=51qK1C-adTL&ref=plSrch

USB fan with a speed control knob built in. Saves some work, can be powered from my phone charger, works for the USA crowd.

Was about to get some magnets from eBay. Will 10mm x1mm discs work?

I found to 10 x 1mm more likely to throw the bar. I used the 10x 5mm but you could always super glue a few 1mm together if the force is not with you.

I fail to see why these button/disc magnets continue to be used by brewers. They are really not very good for this job. Their magnetic field is tiny and they throw the stir bar too easily, and yet people persist. HDD magnets are also not large enough for big stir bars, but their polarity is correct at least.

I have had excellent success with rectangular magnets:
Untitled by vortexau, on Flickr

http://www.ebay.com.au/itm/5pcs-Rectangle-Strong-Block-Bar-40-x-10-x-4-mm-Magnets-Rare-Earth-Neodymium-N35-/141508331995?hash=item20f28dc9db:g:SKoAAOSwofxUjqFh

I don't recall ever throwing a stir bar. Bar locks in as soon as it passes over the magnets, no messing around with trying to get it to line up like when I built my first one with button magnets. Just make sure they're organised so that one side is N and the other is S facing up, but that's no different to the button magnets.

 

[klangers]

I also use rectangular magnets after fussing around forever with little crap ones. Mine just happily sit on the fan with no glue whatsoever. A little $20 PWM speed controller from jaycar and off we go.

A few observations about bar throwing:

• Bars seems to be thrown at certain speeds when stirring. These typically seem to be lower speeds, or when the fan is accelerating the bar slowly (ie winding up the speed dial slowly) in still water. Water currents play a part
• Bars are almost always thrown if the flask is not at least approximately concentric with the fan.
• Bars are almost always thrown if the axis of the flask is not parallel with the axis of the fan

Investigate these problems before assuming MOAR MAGNETSSSS!

 

[Benn]

How would one go about incorporating heating into a DIY stir-plate?

 

[Mardoo]

???

 

[vortex]

How would one go about incorporating heating into a DIY stir-plate?

Not sure why you'd bother. Room temp is all you need for starters; and it can be boiled on the stove to sanitise.

 

[Benn]

I've seen heated stir plates for about $80 at a home brew shop. Room temperature in my shed (where the kids can't fiddle with brewing equipment) mid-winter is about 10 degrees most days, not ideal temps for yeast cultivation. Not always practicle or enough room to in the Ferm fridge to ferment and grow starters simultaneously.
Cheers,

 

[GibboQLD]

How would one go about incorporating heating into a DIY stir-plate?

If you're looking to make an all-in-one unit, you could do something with a peltier or three, I guess -- just have to build in some kind of temperature controller / cut-out to stop it from cooking your yeast if/when the controller fails.

If you're not too worried about how it looks as long as it gets the job done, there's a few ideas over here, the most practical being Brewer Pete's:

small thin plastic tub of water on stirplate, fishtank heater in that and flask in the water bath for me

 

[Mattrox]

I got my USB fan from amazon today. It's easy to take apart. Here is the result.

image.jpg

Only needs a few parts to turn it into a stir plate.

On the lowest speed setting it pulls a whirlpool. I can turn it up a touch. It does throw the stirrer when going too fast. My stirrer has the rib in the middle.



Now I just need a box for permanent mounting.

 

[IsonAd]

Interested in giving this a go. How much was shipping on the fan? Wasn't their one on eBay or something that would have been easier than going through us amazon ?

 

[IsonAd]

[Edit- double post]

 

[Mattrox]

Interested in giving this a go. How much was shipping on the fan? Wasn't their one on eBay or something that would have been easier than going through us amazon ?

It wasn't too expensive. I think the fan was $11 US at the time and shippung about $7 US. It ended up pretty much spot on.

There was one on e-bay but I don't think it was branded. So I went the fan that the Americans had used, which I know worked for them.

 

[megabyte]

It does throw the stirrer when going too fast. My stirrer has the rib in the middle.

Nice build, I like that it uses a 5v USB fan since power adaptors can make up a big portion of your build cost. I wouldn't worry too much about the pivot ring in the middle of your stir bar, I've never found it to have much effect of the magnetic retention, but it will cause it to rattle and the noise may send you bonkers overnight

What size are those magnets though, they look a little small?

 

[Mattrox]

Nice build, I like that it uses a 5v USB fan since power adaptors can make up a big portion of your build cost. I wouldn't worry too much about the pivot ring in the middle of your stir bar, I've never found it to have much effect of the magnetic retention, but it will cause it to rattle and the noise may send you bonkers overnight

What size are those magnets though, they look a little small?

They are tiny. I have them stacked 2 high. Not sure if that matters at all.

I would go for bigger magnets if I did it again. But it works, so meh....

Yes it does rattle but overall it's not too bad. Now I have to put it to good use. (And finish the build)

 

[verysupple]

Commenting on a pretty old post, but others might find it useful.

I had one of these that made my fan let off a high pitch whine. Never bothered to find out why and lost it in the shed somewhere.

I've got a couple of DIY stirplates with DC jacks and would just use a different voltage transformer depending on starter size but recently updated them with a couple of these which seem to work fine and easy to combine into the build.

The high pitched whine from the PWM is the transistor switching at the frequency determined by the RC circuits. I built my own, so I just swapped one the resistors for a different value and the whine went away. I.e. I changed the switching frequency to an inaudible one. So, if you're handy with a soldering iron, the problem goes away for the cost of a resistor - about a cent or two.

Happy brewing.

 

[megabyte]

I would go for bigger magnets if I did it again. But it works, so meh....

Exactly. No need to spin it like crazy so long as there's a decent vortex IMO. Good luck with the rest of your build!

 

[Camo6]

Commenting on a pretty old post, but others might find it useful.


The high pitched whine from the PWM is the transistor switching at the frequency determined by the RC circuits. I built my own, so I just swapped one the resistors for a different value and the whine went away. I.e. I changed the switching frequency to an inaudible one. So, if you're handy with a soldering iron, the problem goes away for the cost of a resistor - about a cent or two.

Happy brewing.

Thankyou, my good man. I shall sleep soundly tonight!