Another DIY stir plate

[Luke84]

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.

 

[Yob]

No speed control?

 

[Luke84]

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

 

[Yob]

Certainly helps with flasks of different sizes...

 

[Luke84]

Sorry YOB do you think something like this would work?

 

[takai]

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

 

[Luke84]

Thanks takai would this do the job

 

[SBOB]

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

 

[dblunn]

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

 

[Camo6]

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.

 

[btrots87]

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.

 

[Edgebrew]

+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.

 

[takai]

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.

 

[philmud]

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.

 

[Camo6]

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

 

[philmud]

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.

 

[lael]

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

 

[Wilko76]

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

 

[adryargument]

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.

 

[SJW]

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