My Stirplate... Cheap and Easy Build...

[Flomaster]

throwing bar = weak magnets, double or triple those bad boys up

-=Jason=-

 

[Snafu]

I've used a 5.7v, 10v, and 12v power supply to see which one works the best. The 5.7v works but only gets a inch dimple or so for a vortex. The 12v throws the bar immediately. The 10v spins for a few seconds before it throws the bar.

The bar is 2 x 3/8. I think its probably too large but its the only one I have and they are expensive since the shipping on them is alot and I don't want to pay another $17 to see if it fixes the problem.

Any suggestions on what to do to perhaps make the 10v work or should I just settle on the 5.7v.

You can also check the yellow pages for local lab supply shops, I found one right around the corner from my office (they typically don't advertise) and paid 2 bucks each. I've asked for a catalog to see what else they have.

 

[camiller]

throwing bar = weak magnets, double or triple those bad boys up

-=Jason=-

Could also mean that the magnets are not quite lined up directly across the center of the fan such that at lower speed the bar doesn't get thrown but at faster speed it does.

 

[jtkratzer]

I've been doing a bit of reading and looking at different designs to build a stir plate and a question comes to mind right away: is there any reason people are not removing the "fins" from the fan to reduce the workload on the motor within the enclosure or is anyone drilling/cutting "exhaust" holes for the air flow to move and keep the circuit board cool for those using an LM317 solution?

 

[Anthony_Lopez]

I've been doing a bit of reading and looking at different designs to build a stir plate and a question comes to mind right away: is there any reason people are not removing the "fins" from the fan to reduce the workload on the motor within the enclosure or is anyone drilling/cutting "exhaust" holes for the air flow to move and keep the circuit board cool for those using an LM317 solution?

You could definitely do either of those, but it's just a matter of effort. I'd prefer to not risk ruining a fan.

 

[FrewBrew]

So Im sitting around the other day going through my computer closet saying to myself "I bet I could make myself a stir plate out of a fan and some rare earth magnets." Before I bothered planning it out I searched real quick and you went ahead and wrote it all up for me.

Thanks for the great write up, Im stopping by the shack tomorrow!

 

[Homercidal]

throwing bar = weak magnets, double or triple those bad boys up

-=Jason=-

Which is why I have ordered some magnets off ebay, even though I have TONS of the hard drive magnets laying around the house and work.

I got a whole bunch for a few dollars. I'll probably even invest in a PWM circuit to control the speed with. The simple Potentiometer I am currently using works fine, but the PWM is nearly infinitely variable, and only costs a few dollars.

 

[Flomaster]

Which is why I have ordered some magnets off ebay, even though I have TONS of the hard drive magnets laying around the house and work.

I got a whole bunch for a few dollars. I'll probably even invest in a PWM circuit to control the speed with. The simple Potentiometer I am currently using works fine, but the PWM is nearly infinitely variable, and only costs a few dollars.

I need to look into that PWM option

-= Jason =-

 

[eppo]

Hard drive magnets work fine.
Just an FYI, I used to use some cheap ebay stir bar, I lost it and picked up a 1 inch Fisher stir bar. This one is a lot heavier and much stronger! I can't throw it, even at high speed!

 

[Homercidal]

Hard drive magnets work fine.
Just an FYI, I used to use some cheap ebay stir bar, I lost it and picked up a 1 inch Fisher stir bar. This one is a lot heavier and much stronger! I can't throw it, even at high speed!

Yeah, that's what I thought when I built mine, but after several uses, it tends to throw the bar, and it's MUCH easier to line up a couple of round magnets than to find the magnetic center of hard drive magnets.

Well, we'll see anyway. I haven't had time to actually load them up yet, but theoretically it should work much better. And I might buy a larger stir bar and pass my small one down to my buddy...

 

[Anthony_Lopez]

FYI- most commercial stir plates use bar magnets like the ones listed in the original post

 

[Homercidal]

I need to look into that PWM option

-= Jason =-

I bought a Futurekit DC Motor Control Circuit to power my Boil Kettle. The idea was that swapping a resistor allows the timer to work well for powering an SSR connected to the 220V heating element, allowing a precise boil rate on the cheap.

The circuit, as designed, works for controlling 12V DC motor speeds, like those used in computer fans. After I built the circuit (it was not prebuilt, like I thought, but only took 1/2 hour to solder together including getting out the soldering iron and stuff and putting it away again). I tested on a computer fan and the fan smoothly goes from very nearly nothing to full speed. Not like the potentiometer that I stole from some other project, which has a "lowish" setting and a very small range.

it works so well that I'm considering buying a few to save on shipping (The circuit costs less than $8, but the shipping doubles that) and building a few more stirplates, and of course I'll need another one for the BK!

Here is a link to a place selling the kit. There are others selling the same thing:

http://www.bakatronics.com/shop/item.aspx?itemid=383

 

[camiller]

FYI- most commercial stir plates use bar magnets like the ones listed in the original post

Currently the original post points to these at K&J Magnetics, but those are magnetized through the 1/8" thickness such that the large flat faces are the poles. I am thinking that if you really want a bar magnet, this one or this one would be better since they are magnetized along the long axis. Or maybe this one which is flatter.

 

[Schnitzengiggle]

FWIW, K&J Magnetics may not be the cheapest, but they have great service, fast shipping, and quality magnets. I used them when building my stirplate.

 

[Hebby]

Just finished making this last night. Took about 45 minutes. Used solder and shrink wrap for all the connections. I used a 12V Linksys router power supply. I haven't received my magnets yet but they should be here soon. Thanks for the post it made it easy to put together.

 

[Cranapple]

Thanks a ton Anthony, I built this in my spare time over the last couple of weeks. It was a wicked fun project, as I've been wanting to start learning a little bit about electricity (I'm a mechanical guy) and I was able to do an "electronics" project related to beer! Total cost was $20-$25 (I burned out my first potentiometer and had to buy an extra package of quick disconnects.)

Mine works great, although the 1" stir bar only creates about a 1" deep vortex at full speed (even in a 1/2 gallon growler though). I know that's sufficient for what it needs to do, but I'll probably still switch it out with an 8-12V power supply if I find one for free somewhere.

I'm going to try my first yeast starter this weekend, on my first lager. I hope that's not too much new stuff in one try, lol.

 

[Anthony_Lopez]

Currently the original post points to these at K&J Magnetics, but those are magnetized through the 1/8" thickness such that the large flat faces are the poles. I am thinking that if you really want a bar magnet, this one or this one would be better since they are magnetized along the long axis. Or maybe this one which is flatter.

I agree. those would work as well. I used the ones listed in the orginal post because I wanted to use a high voltage power supply and have two stacks of magnets. I personally like this one for a long bar application. I'll order a few and see what I get...

 

[jtkratzer]

I just harvested 6 magnets from some hard drives on the way to be destroyed at work and it got me thinking when I was stripping these down to the bare chassis - is anyone using the motor from the drive that spins the platter?

 

[Anthony_Lopez]

I just harvested 6 magnets from some hard drives on the way to be destroyed at work and it got me thinking when I was stripping these down to the bare chassis - is anyone using the motor from the drive that spins the platter?

A few of our electrical engineers and I tried to do that last year and we couldn't figure it out. Granted we only spent 15-20 minutes messing with it. From what I remember, they are only meant for very high RPM with light loads.

 

[Homercidal]

True, they have low torque and high speed. It only takes a light touch to drag them down.

 

[jtkratzer]

Noted. They're going in the trash.

 

[weconway]

This has been on my "to make" list for a while. I've been collecting components for a few weeks.

I wired everything up tonight to make sure it would work. Well I couldn't get the scavenged fan to start turning on its own power, and the vortex it created was a bit weak.

So I dove into the donor scrap PC that gave up the HD magnets, and found this guy:

It works awesome now. Sometimes you just need a bigger hammer.

I don't know why I thought that puny fan would work. Now I just need to build the enclosure and wire it up.

William

 

[FrewBrew]

I built one this weekend using a spare 5.25" fan. It was a bit of a tight fit, but it worked. The tension of the case was enough to hold the fan in place and didn't necessitate any bolts.

Great DIY thread, seems like this would go great in a FAQ.

 

[wegz15]

Ok, So I have a question. I just built one of these. I'm using half inch rare earth magnets from the hardware store. I used a pvc coupler to get the magnets off the fan like the fella at stir starters. I don't have a stir bar yet. For now I am tinkering with a 1 inch bolt with the head cut off.

I tried using this with a glass jar and it seems like there is not enough magnet power. Would the magnets get a better grip on an actual stir bar? What am I doing wrong??

 

[Anthony_Lopez]

It depends on the strength of your magnet and the distance between the magnet and the bar. I wouldn't give up on your magnet until you have your stir bar.

 

[camiller]

Ok, So I have a question. I just built one of these. I'm using half inch rare earth magnets from the hardware store. I used a pvc coupler to get the magnets off the fan like the fella at stir starters. I don't have a stir bar yet. For now I am tinkering with a 1 inch bolt with the head cut off.

I tried using this with a glass jar and it seems like there is not enough magnet power. Would the magnets get a better grip on an actual stir bar? What am I doing wrong??

It depends on the strength of your magnet and the distance between the magnet and the bar. I wouldn't give up on your magnet until you have your stir bar.

Yeah, what he said. The stir bar is itself magnetic so the magnets on your stir plate should grip it better than just a bolt.

 

[Cranapple]

I'm not sure if this applies to you or not wegz15, but I had an issue with mine where I actually had my drive magnets TOO close to the top of the box. Mine worked with bolts/solid carbide cutting tools/paperclips, pretty much anything; but only when I put in a 1/2" to 5/8" spacer on top of my project box. The magnet was pulling down so hard that the friction was keeping the items from moving. If I picked up the flask/growler I was testing with, the objects all of a sudden started spinning as the fan motor was able to move.

I found this to be a problem even with my teflon-coated magnet, the forces were just too great and it wouldn't turn. It did work once I put water/wort in the flask, since that lubricated the bottom of the stir bar enough to let it spin.

Hopefully this helps someone else if it doesn't help you.

 

[wegz15]

I had water in my mason jar. I didn't want to use my flask with a bolt to avoid scratching. I ordered two stir bars, 1" and 2". I'll have to try giving it more space. Thanks for all the suggestions and feedback

 

[Hebby]

Just finished mine using the magnets from Ace Hardware previously listed in this post. 6 of them were less than $5. Used a linksys 12V power supply from an old wireless router. 1 inch bar works great 2 gets thrown. Photos are on minimum power. Thanks for the writeup on this.

 

[Flomaster]

Just finished mine using the magnets from Ace Hardware previously listed in this post. 6 of them were less than $5. Used a linksys 12V power supply from an old wireless router. 1 inch bar works great 2 gets thrown. Photos are on minimum power. Thanks for the writeup on this.

How many magnets did you use on each side maybe double up for the two inch bar?

-= jason =-