# Another DIY stir plate



## Luke84 (11/6/15)

So I thought I'd share my diy stir plate with every one. 
usual computer fan 4x rare earth magnets the placement of these are critical 
They must be the opposite in polarity for the stir bar to turn took me a few attempts to get that lol so here it is.


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## Yob (11/6/15)

No speed control?


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## Luke84 (11/6/15)

Nar not yet off or flat out, will be add speed control in future just needed it for yeast propagation.


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## Yob (11/6/15)

Certainly helps with flasks of different sizes...


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## Luke84 (11/6/15)

Sorry YOB do you think something like this would work?


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## takai (11/6/15)

120ohm potentiometer will do just fine, wire it inline.


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## Luke84 (11/6/15)

Thanks takai would this do the job


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## SBOB (11/6/15)

Luke84 said:


> Sorry YOB do you think something like this would work?
> 
> 
> 
> ImageUploadedByAussie Home Brewer1434009285.659890.jpg


they work perfectly and technically better than a potentiometer as its a PWM output controller (e.g. output is always 12v just turned on/off rather than a drop in voltage to the fan)

Used exactly the same item for the stir plate I just built


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## dblunn (11/6/15)

Hi all,
I bought a cheap LED dimmer off eBay, works fine in my stirplate (also in a Tupperware container).
Dave


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## Camo6 (12/6/15)

Luke84 said:


> Sorry YOB do you think something like this would work?
> 
> 
> 
> ImageUploadedByAussie Home Brewer1434009285.659890.jpg


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.


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## btrots87 (14/6/15)

Camo6 said:


> I had one of these that made my fan let off a high pitch whine.


+1

Had exactly the same item and got a horrible high pitched noise when I used it with a couple of different fans. Ended up scrapping it and just using a potentiometer instead. Works fine.


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## Edgebrew (15/6/15)

btrots87 said:


> +1
> 
> Had exactly the same item and got a horrible high pitched noise when I used it with a couple of different fans. Ended up scrapping it and just using a potentiometer instead. Works fine.


Computer shops do sell fans that are designed to reduce the noise from PWM.


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## takai (15/6/15)

Luke84 said:


> Thanks takai would this do the job
> 
> 
> 
> ImageUploadedByAussie Home Brewer1434011465.352691.jpg


Ooops, missed this.

Something like this would work: http://www.ebay.com.au/itm/321743555938

You can probably find one at your local computer shop, and if you ask nicely they may even give you one.


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## philmud (10/8/15)

Didn't want to start a new thread, but I'm wondering if anyone has had the experience where the fan on their DIY stirplate won't turn while the magnet is attached?

The wiring is all fine because the fan turns without the magnet and a multimeter suggests that the fan is getting 12V when the potentiometer is cranked up.

Im using a large magnet from a hard drive (see picture) and I'm wondering if it's just too big, and if so, is the solution a more robust fan (I'm using this one: http://pages.ebay.com/link/?nav=item.view&alt=web&id=171576257834) or smaller magnets.


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## Camo6 (10/8/15)

What voltage power source are you using and its amperage? If you push start it will it spin?


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## philmud (10/8/15)

Using a 12v power supply & I think 2.0A. Wouldn't spin, even with a push. I raided a laptop hard drive for a smaller magnet, which worked, but it also works using some toy coins as spacers, so I'll probably go with that.


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## lael (10/8/15)

Strong magnets can interfere with the fields needed to drive the fan if the fan is on the mild side.


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## Wilko76 (19/8/15)

I had the same issue when I doubled up my magnets. Fan wouldn't spin anymore. You can glue the magnet to a large washer and it will disrupt the magnetic field enough to make it work. I used a holesaw to cut a disc out of 1mm thick plate, because height was an issue, and it was enough to get it spinning again. Or up the power supply, but I'm only using a 9v 3amp and it gets a nice vortex at 3/4 speed but I need to crank it flat-out to make it start spinning


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## adryargument (1/9/15)

Fans have wire coils in them. If you rotate the fan with the magnet on it you will *feel* it cling to the 8 coils as it transfer over them. 

Computer fans generally need 7+ volts to spin-up and 4+ to maintain spin. The magnet would increase this. If 12v can't spin-up then she ain't gonna work.


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## SJW (1/9/15)

Wilko76 said:


> I had the same issue when I doubled up my magnets. Fan wouldn't spin anymore. You can glue the magnet to a large washer and it will disrupt the magnetic field enough to make it work. I used a holesaw to cut a disc out of 1mm thick plate, because height was an issue, and it was enough to get it spinning again. Or up the power supply, but I'm only using a 9v 3amp and it gets a nice vortex at 3/4 speed but I need to crank it flat-out to make it start spinning


+1 that's what I did, and it works a treat


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## Mattrox (12/11/15)

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?


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## roastinrich (12/11/15)

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.


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## Mattrox (12/11/15)

Thanks. I got 8mm x 5mm discs.

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


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## Mattrox (20/11/15)

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.


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## vortex (10/12/15)

Mattrox said:


> 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
> 
> ...





roastin said:


> 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.


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## klangers (10/12/15)

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!


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## Benn (10/12/15)

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


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## Mardoo (10/12/15)

???


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## vortex (10/12/15)

Benn said:


> 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.


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## Benn (10/12/15)

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,


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## GibboQLD (10/12/15)

Benn said:


> 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:



Brewer Pete said:


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


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## Mattrox (11/1/16)

Mattrox said:


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





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.


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## IsonAd (17/1/16)

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 ?


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## IsonAd (17/1/16)

[Edit- double post]


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## Mattrox (17/1/16)

IsonAd said:


> 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.


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## megabyte (1/2/16)

Mattrox said:


> 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?


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## Mattrox (1/2/16)

Michael Burton said:


> 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)


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## verysupple (1/2/16)

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



Camo6 said:


> 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.


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## megabyte (1/2/16)

Mattrox said:


> 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!


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## Camo6 (1/2/16)

verysupple said:


> 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.
> ...



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


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## Mattrox (6/10/16)

I finally got my USB fan stirplate boxed up. I had been running it under an upside-down plastic container. Now it is in its own Jaycar box.


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## Mattrox (6/10/16)

A shot of the inside. I raised the fan using m3 nylon nuts, screws and spacers.

I had a spare reptile vivarium vent so I whacked it in.


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## Mattrox (4/11/16)

I bought these egg shaped stir fleas off ebay to replace the ribbed bar shown in the middle. Much less noise. 

Really happy with them.


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## Mardoo (4/11/16)

I agree. I also have the egg/suppository-shaped bars. They totally rock.


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