My homebrew stirplate

+1000! Go Sirsloop!

(Wanna tell me how to fix my electric? Its wiring is toast.)

lol... I'm no electrician... took me a little while to find the right leads to solder to.

I just got mine all done and together...but i can't get mine to slow down to a crawl actually when the pot is all the way down or not even all the way down the fan completely stops spinning i am about to go read my voltage at the the lowest setting... anyway my stir bars come tommorow so im gonna give her a spin

well it does vary from about 1.28v to 12 but the fan will only turn at a min of about 5.2 volts sseems to fast to not sling the stir bar owel we will find out

kjones said:

I just got mine all done and together...but i can't get mine to slow down to a crawl actually when the pot is all the way down or not even all the way down the fan completely stops spinning i am about to go read my voltage at the the lowest setting... anyway my stir bars come tommorow so im gonna give her a spin

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Move the fan farther away from the magnets. The force of the magnets is too strong and is waxing your fan.

Silly question:
Is it possible to just use a regular old 120V desk fan and put a light dimmer switch in-line instead? I have a feeling that this has been asked already but my search-fu is failing me.

Well, I got my stir bars in today and and none of them will work they just kind of spin a little by like following mags on one side of the fan then sling off. I wish Mrsalty the original poster would chime in... guess hes not around anymore or maybe yuri someone with some experience building these things i pm both with no response well i guess if you two see this reply or someone elso that knows something i would be greatly appreciative for some info...

by the way... the magnets i used are 4 1/2 dia. x 1/8 thick rare earth magnets. there are 2 glued together on each side

are the reverse poles sticking up?

+1 on sir. Definitely sounds like the magnets on both sides have the same pole facing up. With those size magnets, you should have no issues if they are oriented correctly.

Originally Posted by camiller

That one is out of stock currently, I'm considering this one http://www.newegg.com/Product/Produc...82E16835200021

Cheaper also.

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That rosewill fan is a POS! The controller that comes with it is nice. If you put a hard drive magnet on that fan it locks up the blades from turning. I ended up ditching the fan and just using the controller on a beefier fan that I had laying around. If you end up using that controller, a 9V power source is just about right for low to stop the blades and high to spin a 2000ml flask at an insane rate. I tried a 5V and it was ok... pretty good for like 1000ml. I put on a 12V source and it would make a MASSIVE vortex from top to bottom of a 2000ml flask, but at low the fan moves so its hard to get the bar centered on the magnet without killing power.

I'm going to work on fine tuning my setup now... but it currently includes a beefy 12V 120mm fan, machine screws to lift a 120mm fan holder up above the magnets, three hard drive magnets stacked on the fan, 1-3/8" stirbar... and a 9V source. I'm not 100% sure how I'm going to hold it all together yet, but so far I just cut a piece of spare plexiglass in a 140mm square so it can fit on top of the fan, padded with that kitchen no-slip stuff. Works good... pics/video tonight probably...

I was thinking about just removing the center section of the fan guard to make room for the magnet.

Thats not tall enough for multiple magnets unless you boost up the grill with long machine bolts and washers...could work tho. I used three hard drive magnets for super duper crazy strength. I had the thing at full blast with 12V going into the fan... like 2400rpm. There was hardly any water even touching the stir bar anymore cause the vortex was so violent! HAHA!! Works like a champ!

I've been working on one of these, just building it from the parts around the house. I don't have an old train controller so I'm attempting to use a light dimmer switch. I cut apart an extension cord, wired the controller in there then plugged in a 9V converter that I had (No idea what it used to go to) and then cut that up and wired it to the fan. It works alright (Still waiting on the stirbar) but I think the magnets interfere with the operation of the fan so I need to find a way to lift the magnets away from the fan some it seems.

conpewter said:

I've been working on one of these, just building it from the parts around the house. I don't have an old train controller so I'm attempting to use a light dimmer switch. I cut apart an extension cord, wired the controller in there then plugged in a 9V converter that I had (No idea what it used to go to) and then cut that up and wired it to the fan. It works alright (Still waiting on the stirbar) but I think the magnets interfere with the operation of the fan so I need to find a way to lift the magnets away from the fan some it seems.

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Thats exactly the problem I had with that rosewill fan. When you place the magnet on the fan it must pull on some metal part inside the fan which makes the fan press up against the motor and it gimps the fan due to friction. This other fan I had didnt seem to be effected by the magnets, so it got the job. I used a folded up piece of paper on the rosewill fan to seperate the magnet and the fan, but its a wack setup.

I've been pulling magnets out of hard drives for years. I got a pretty good stack saved up. Just ripped another apart a moment ago. Also tore apart a printer selector switch that is now obsolete. Should make a great enclosure. Just tossed out about 8 computer case fans a month ago. Typical...

I've found that you can remove the magnets by heating the epoxy that holds them to the shield. BUT, if you heat too much, you destroy the magnet, so I vise the shield, use a torch to slowly and carefully heat the BACK of the shield while prying the magnet with a small screwdriver. Sometimes beating them off will crack them.

I should have pretty much all of the components save for the IC. A small box of wall warts should yield at least one suitable for the project.

Now to buy a stir magnet!

1-3/8" magnet seems to work best with hard drive magnets. If you go bigger the poles dont line up that well.

I decided to rip into some old electronics to see what I had laying around that would do the trick. I started off with an old case fan, but it was spinning way too fast to catch the stir rod (piece of steel for now). I opened up an old cdrom drive and lo-and-behold, just what I was looking for. A motor and set of reduction gears. It is the motor used to drive the read-head/laser back and forth. A quick unscientific count says its running about 200 rpm give or take a lot. I hot glued an old hard drive magnet on there, poof, insta stir plate

I think I will probably keep working on this, I would like it to spin a little faster. Its not as much fun as soldering together a PWM circuit, but it works.

lol... cdrom stirplate? I think it would have been easier to put a lower voltage supply on the fan, but to each his own. If it works then more power to you!

I finally got two magnets out unharmed. Some companies seem to use a ton of epoxy but I found one that was barely tacked in with a spot of glue. I guess two stacked will be fine.

yeh probably... the key is just to get the bar as close to the magnets as possible... no doubt you'll get it

sirsloop said:

lol... cdrom stirplate? I think it would have been easier to put a lower voltage supply on the fan, but to each his own. If it works then more power to you!

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Well, Its icy outside and its like 20 minutes to Radio shack. Blah blah blah... I still wanna brew this weekend, but don't wanna venture out. I think I will build a more permanent solution in the future, but this is gonna have to do for this batch. Its stirring away as I write .

Any suggestions on where to find a stir stick around town? or, anyone got one for sale for less than the $25 minimum order I saw online? Mine is ready to try out (less than elegant, but I think it will work well.)

Well, I tried it without speed control, and the 6V supply seemd to be OK. Need to actually get a stir stick to know for sure. I also tried with a rheostat, but it didn't seem to make hardly any speed difference. Hmm...

I think at this point, the most important thing to think about is making some sort fo stir stick to test with. Oh, and also how to configure some funky LED lights to light up the Starter! BD

Got my Stir plate pictures. Used an old printer selector box, ripped the guts out, and stuck a case fan in there. I ended up using a rheostat, and a power switch. Still doesn't go slow enough for my taste, but I could modify a bit to slow it down easy enough.

I used a punch to sink the screw holes a bit, so the screws sit flush with the surface. This also serves to lower the fan a bit, so the magnets are near flush as well.







I didnt' have a real stir stick, so I cut of a piece of steel laying around. It would work better if I had a ring in the middle to pivot on. Still creates a vortex.

I need some advice on magnets.

I went to my local Radio Shack. They have one size of a RAre Earth and it is really small. They do though have a good stock of larrger magnets. Does the type or shape on magnets matter at all?

How does one select an appropriate magnet?

Yet another question from an (electrical) idiot....

I have two choices of power supplies, and would like to do this as cheap as possible. I have the fan, I have the hard drive to tear apart. I have one plug with an output stated as 5.9V====375mA and one that says 12VDC 300 mA. Which one is better, and if I use the 5.9V will I need a speed controller? I was going to buy the project box from RS but was hoping not to buy anything else there...the fewer parts I need to buy, the more likely SWMBO is to let me do it

There are quite a few variables to consider, which makes your question nearly impossible to answer without asking a whole bunch of questions in return.

Best advice is to tell you to tear into that hard drive, mount a magnet to the fan, try out the 5.9v PS connected to the fan. Put the fan/magnet in a vice with a piece of plastic over it and see if you can stir anything.

Adjust design as necessary. The parts at Radio Shack cost like $10. I used an enclosure from an old computer power supply, which had a rocker switch, so you only need the components to build the circuit, and a circuit board.

Gammon N Beer said:

I need some advice on magnets. I went to my local Radio Shack. They have one size of a RAre Earth and it is really small. They do though have a good stock of larrger magnets. Does the type or shape on magnets matter at all? How does one select an appropriate magnet?

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JoAnn's Fabric. They sell an 8 pk of ceramic 3/4" round disk magnets that are FAR more powerful than they look. I'd use 2 on each pole, and then you have 4 left over for the fridge. Cost me less than $4, easier than ordering rare earth mags online.

The tiny R.S. neodymium 1/16" or 1/8" or whatever magnets suck. Ignore them, they're expensive and weak.

Hi, I have been building a stirrer based on the instructables web site.
scrapped a 350 w power supply for an enclosure and decided that maybe
the cooling fan would be all rpm and no torque. Substituted a motor from a
rechargable vac and built an overelaborate bracket for it. My problem is baffling,
the ptfe stir bar I bought on eslay spun on the WRONG axis! (like a log rolling down a hill) substituted a piece of allen wrench cut down and it works better. now to encapsulate the bar??? wonder if maybe my magnets were too close togather for the stir bar? lots of things to try. thanks for a great topic!

Try using one magnet, I ran into a similar issue and that fixed it. I know have a 1 inch sitr and a single magnet. With 2 Plates it's awesome.

Hmmm....I have two choices here...I have all of my parts, and I have to make a choice. I have two nice half moon magnets that I snatched from an old hard drive, or I have two 9/16" x 1/4" Neodymium magnets from Cynmar. I"m using a 120mm fan from Radio Shack, the rheostat that everyone has recommended, and I have my choice of 5.9V or 12V power supplies (old cell phone chargers). Anybody have any input on one set of magnets or the other? Or all four?

I've had most of the parts for this thing for months, and I finally got motivated to put it together. Originally I had planned to mount it in a cigar box, but I found this more appropriate (and more water resistant!) enclosure last week at All Electronics.

Works great! The speed is smoothly adjustable from "Off" to "Warp Drive," with plenty of range in between. I'm looking forward to my next starter.

I am still having issues finding magnets that work

98EXL said:

I am still having issues finding magnets that work

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I used these magnets and this enclosure, both from All Electronics. The rest of the stuff (fan, wall wart, regulator, pot, knob, etc.) I already had in my shop.

Hello

I completed my stir plate and am now testing it and running into a problem.

The stir bar keeps flipping out. Or, it simple rattles and shakes or actually jumps.

I am using rare earth magnets from hard drives and have four of them.

Although my motor can be slowed, is it still too fast?
Are the magnets too powerful?
Could it be that the magnets are too close to the bar?

Any ideas?

I think it is for making a starter with your yeast. To stir/keep things moving. Not certain though.

Nevermind, man I need some rest. Was looking at end of 1st page.

So I think you need to scale back to one magnet. This is same issue i had and you just set the magnet up and test test test. I that a single magnet set off to one side worked best for my setup.



Let me know how it works.

Odd, I concede... but why not get rid of the fan blades altogether..??

That is they are still pushing air, taking up precious power. Lopping them out should be done carefully, so the unit remains balanced.

I am sorry were we talking fan blades or magnet? I must have missed something. My bad, I have no idea why lop off the fan blades. Didn't really think about it to be honest.

Something to try though, let me know how it works out.

OK...

I am testing my stirplate and this is what I get.

My stir bar will rotate, but I am not getting the speed I need to create the vortex. Is it that the motor rotates too fast for the bar to keep up?