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Magnetic Stirrers / Stir Plates & Bars

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#41 Hippie3



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Posted 07 May 2006 - 06:59 PM

by blacklabrat

I would like to introduce my new little friend...........



OK, Right off the bat let me make it clear that I can take no credit for this. It is an idea that has been ripped off and inspired by several others who have done the DYI magnetic stirrer plate method. It works great, took me less than an hour to make and the best didn't cost me a dime. FREE! Just scraped up a few items I had laying around the house.

Here's how it was done:



~ Started off by mounting the fan to a block of scrap lumber. Connected the fan to the transformer. Originally I was going to add a dimmer switch, but after testing I deemed it unnecessary.

~ Next, I took a canning lid and hot glue gunned it to the top of the fan. Place the magnet in the center of the canning jar lid. Tested placement by plugging unit on to make sure there was no wobble. Hot glue gunned it once the magnet was properly centered.


~Then I cut two blocks of lumber about 1/8" taller than the height of the fan/jar lid/magnet assembly. Mounted these to the side of the fan with glue and screws. Fixed a square of plexiglass to the blocks. This is the base surface where the LC jars sit.

Turned on to make sure that the fan was spinning freely.

Check. Everything is running quiet and smooth

Now I need some stir rods................Hmmm. Ebay? Nah. Screw buying them!
I was now determined not to shell out any cash for this project. After playing around with several ideas, many which were too loud, slow or would require me spending some of my precious beer money .....

I was reminded how sometimes the simplest solutions are the most effective.


A small piece of wire about 1/4" long is quiet, effective and best of all CHEAP!

I tested it by placing a small piece of toilet paper in the jar w/ H2O and with in an hour it had broker it into small fibers.

Yeah yeah. I can hear it now."Isn't the wire going to rust?"

Eventually. But not before the LC is done. They are essentially disposable, costing you about 10 cents per 100!

And there you have it.

How well does it work? Check out the first pic!

It spins like Dorthy in a tornado.

I first attached the canning lid to the fan blade with super glue, making sure that it was absolutely centered. I then played around with the placement of the magnet making sure that it spun with out wobbling. As soon as I had the placement correct I outlined the magnet w/ a sharpie, and secured with glue.

Its not really necessary, just the way I happened to do it


Need to warm up the temp of your LC? Try this:

Made one minor improvement to the Sir Mix-A-Lot magnetic stirrer.

I usually do my LC in temps around the high 80s. Currently temps in my neck of the woods are about 20 degrees too cold & I'd rather not put the stir plate in the incubator, so........................


My solution:

I removed the plexiglass base plate and temporally replaced it with a 4 quart lexan tub. The tub is outfitted with a aquarium heater set to 87 degrees and a thermometer. (I realize that the heater is a little too large for this particular application..going to get a smaller one this weekend)
I can now dial in to the exact temp I need.

a piece of wire shrink wrap (can get it in small quantities at a hardware store or rat shack) will seal up that piece of wire nicely... slip it in, flame it up, watch it melt over the wire... voila, rust free low cost stir bar....

....doesn't have to be a cell charger, any "wall wort" a/c adapter whose voltage matches your fan (almost always 12 volts) will work. if you don't have one, universal ones are cheap, and sometimes have a switch to adjust voltage. (less than 12v = fan will still spin, but slower = a variable speed control version!) cut off tip, strip wires, twist together with wires from the fan. its ok to be off by a little, eg a 11.5v or 12.4v or such adapter is gonna do just fine with a 12v fan. don't go beyond 12.5v or so or risk burning out the fan, and anything much less than 11v is gonna result in a slow spinning fan. if it doesnt spin or spins backwords, match the wires up the other way around. radio shack also has 120vac fans that will work on current straight from the wall: in which case get a cheapo extension cord, cut off female end, strip and twist up wires in similar fashion. (use of wire nuts and/or lots of electrical tape is a good idea, 120vac can be dangerous if your wires are exposed! the voltage from a DC adapter like a cell charger will NOT harm you, but if the wires touch eachother you end up with a dead adapter)... if wiring the AC variety without an adapter you can't get the wires "backwards" as it will work either way.

#42 dirtyman



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Posted 08 May 2006 - 02:37 AM

A buddy and I tried to wire one up this week. An old computer fan was glued to some wood with a 1/2 pint lid centered and glued on top of the fan, strong magnets (radioshack cheapies don't work, friend found 2 small yet powerful ones inside an old CD player by the laser) centered and glued on top of the lid. Trying to adjust the speed was a bitch, we're still trying to figure that out by experimenting with a couple resistors. Gonna buy a small stainless steel nail for the stirrer inside the jar. I should be done sometime this week and will try to take pictures.

Anyone know where to get some good magnets for cheap? I'm thinking that you need a good grip on the stir bar inside the jar to make it work.

PS: I like the Agar-like typing of that 1st guy hippie quoted above me :p

#43 jestah



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Posted 09 May 2006 - 07:22 AM

After reading this thread (thanks hippie for putting it all together) I was keen to put one together so I did.

I used the basic ideas from the first post but changed the flowing:

I found an old computer on the side of the street and stole the hard drive and a fan. From the HD I took the THIN but STRONG magnets and spent the next hour getting them balanced on the fan. Set it up so you can turn the fan on and off while testing the balance of the magnet. It’s well worth the effort IMHO. Then super glue them in place. I just ran a bead around the edges of the magnets.

Once this had set up I used silicon (same as I used for my airports) to stick the fan to the lid of the case. I used thin coins as stand offs so there is a thin layer of silicon on each corner where the screw should be. I like this as it acts as a bit of a buffer for the small hum my fan has. Wire in the pot and power and wahay one dam fine stirrer. It hold a 1L flask for yeast starters but will also do concaved jars for LC and the like (that y you need the STRONG magnets)

I think spend the money and get a decent water tight box... not only is it a bit safer if you have a spill but it looks so spliffyly good

I will try to get some photos up tomorrow or the next day. Should i make my first tek???


#44 Killjoy



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Posted 10 May 2006 - 05:36 PM

Just finished A DIY stir Plate. Found an Amazingly perfect fan at the Thrift store. (actually 2) $2 for 2 ceramic magnets at Homedepot or A craft store. A dimmer switch spliced into an extention cord and a little super glue.
Only mod to the fans was to cut the gaurd off/level so a piece of old plexi would sit on it.

Total cost about $11 for the 2 of them.

missed the Nail/tubbing idea for a stir bar and tried coating some smaller ceramic magnets ($2 for 8 at same places) in liquid rubber.
Worked great until I ran it over night and came back to a dark Cloudy LC and shreiked about contams, then realized the rubber had rubbed off and the "cloudyness" was tinny bits of the corners of the magnet. Think I'll try tubbing on them and be set!.

Thanks for info to make this idea work!

#45 Phungivore


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Posted 12 May 2006 - 02:09 AM

on this project i learned 1 thing fans do not make good motors if you want it to work like a factory made stirrer. i think i made one pefect for mycology but if you actually wanted it to be like the factory made unit you would prolly want a motor with some tork. once i can find either some gears or pullys to mount on my RC motor i will make a better setup then the fan. any one know of a good source for gears , pullies , and maybe small motors. will have to see if i still got thr RC motor

#46 hogwild



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Posted 12 May 2006 - 03:46 AM

Just built mine today. Its quite basic but gets the job done of course

Small 20mm fan
12volt auto bulb
6 volt transformer
Small Throwaway gladware type container (circular)
platform of some sort(wood, plastic, anything you want to mount it on)
Jb qwik 2 part epoxy
Stainless Steel Hole cover
Electrical tape

Basically the fan was mounted to a platform, in this case it was wood. Instead of using screws to mount it, JB weld was used. A washer was attatched with JB weld in the center of the fan(be sure to center the washer first, and take your time, its well worth it)
The bar magnet was then centered on the washer and JB weld in place. I was too lazy to go buy a rehostat so instead i used a 12 volt auto bulb wired in with the fan.
This bulb serves a dual purpose, it heats up the lc just a tad and also limits the voltage even more so the fan spins at just the right speed.
The bulb was coated with a decent amount of jb weld so that most of hte light is blocked out.
Once you wire your single pole switch in with your bulb and fan you can mount them to the platform using more JB weld or screws if you wish.

Instead of using plexiglass or some other type of platform, i decided to use a circular pp5 rated ziploc container flipped upside down. I cut the sides of the container down to where the top was just about half a centimeter from the spinning magnet.
Jb weld the ziploc thing in place and your stirrer is complete. Like i said.. very basic

Will post pics tomorrow.

#47 Hippie3



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Posted 12 May 2006 - 08:17 AM

any one know of a good source for gears , pullies , and maybe small motors

electric timer
tape recorders

#48 Spark



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Posted 13 May 2006 - 05:15 PM

Magnetic sitrrer vid

The video was recorded by anno.

[Direct Link]

#49 Killjoy



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Posted 15 June 2006 - 08:22 PM

Finally convinced the FOAF to get a picture the Plates I made for him in action...
Just thought I'd share.
As for stir bars
Ceramic Magnets Coated in Rubber rubbed off and chipped,
Various nails in tubbing didn't spin.
Ceramic Magnets in Rubber tubbing work great... Just need to trim the clamped ends properly or they Fly out of control.
only other advice...
test the stir bars before you toss them in. My Foaf has a dozen small LC's with stir bars that don't stir. Time to shake shake shake. and make a few more Ceramic magnet ones.

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#50 BuckarooBanzai


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Posted 15 June 2006 - 08:28 PM

Nice vortex on that closeup. Excellent design.

That naked wire makes me kind of nervous...

#51 Hippie3



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Posted 15 June 2006 - 08:33 PM

you wanna live forever ??

thx for sharing , killjoy

#52 Killjoy



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Posted 15 June 2006 - 09:23 PM

Ground wire?
We don't need no stinking ground wire!

#53 Hippie3



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Posted 06 December 2006 - 07:39 AM

FGL said:
Here are some links :grin: :thumbup:
http://www.users.on....tic Stirrer.htm

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