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

[slakwhere]

flyweed, make sure that the 2 magnets are lying on the fan in oposite polarities. one + and one - up, and you'll have to play with the spacing to get it to work for your stir bar (especially if you plan on using multiple stir bars).

 

[passedpawn]

so you guys are saying I need two smaller magnets on opposite sides of my fan, rather than one long one? I'll give that a shot if so. it's pretty funny to actually watch the stir bar stand up on end vertical and spin that way. but I'll give a couple of smaller magnets a try to see if I can get my stir bar to lay flat and spin properly.

Dan

I've built a few stir plates with 3 HD magnets stacked to get a 1/2" bar to spin full speed in a 4L flask. Click on my gallery to see higher res versions of these pics if they don't come out right.

I was always a little disappointed that my 2" would always get thrown. Then I built another strirplate with small round disk magnets. These magnets are about 1/2" across and maybe 1/8" thick (looks like a large watch battery).

I make 2 stacks, with 3 of them in each stack. The stacks must have opposite polarity for this to work!. The distance between the stacks is about 1.5" (I think). I can now spin that 2" bar. I hotglued a piece of tin (cut from a peanut can) to the fan so I had a place to glue the magnets down.

BTW, the magnets in this second picture below are held by electrical tape. I took this pic during testing and didn't take one after the final glue assembly.

 

[Anthony_Lopez]

so you guys are saying I need two smaller magnets on opposite sides of my fan, rather than one long one? I'll give that a shot if so. it's pretty funny to actually watch the stir bar stand up on end vertical and spin that way. but I'll give a couple of smaller magnets a try to see if I can get my stir bar to lay flat and spin properly.

Dan

K&J sells single magnets with both polarities along their center axis. I haven't used them, however I'd bet they would work as well...

 

[StirStarters]

Fly,

You can use two button magnets or one single bar magnet, both will work OK.

Just make sure that your button mags are arranged with north pole up one side and north pole down on the other.

I think the reason your stir stood straight up is the fact that your drive magnet is magnetized through the short axis instead of the long axis. With a bar magnet you want the poles to be on the "ends" of the bar and not the "sides" if you get my drift.

 

[andersonimes]

I happen to have most of the Radio Shack components for this build already (leftover from an EE class I took years ago). I have one Pot, but it says 500 Ω (500 Ohms) on it. Will this work? I expect not, but I'd like to hear opinions on this.

 

[v2comp]

im sorry if someone already asked this question, but I was building this today and when I finished, the potentiometer wouldnt turn it completely off. is that correct? it seems to be spinning very fast even at its lowest speed.

 

[passedpawn]

I happen to have most of the Radio Shack components for this build already (leftover from an EE class I took years ago). I have one Pot, but it says 500 Ω (500 Ohms) on it. Will this work? I expect not, but I'd like to hear opinions on this.

Sure, like this (click on pic for big version):

 

[Anthony_Lopez]

im sorry if someone already asked this question, but I was building this today and when I finished, the potentiometer wouldnt turn it completely off. is that correct? it seems to be spinning very fast even at its lowest speed.

The potentiometer doesn't work as an on/off switch. It will only vary the voltage from the DC power supply going to the fan.

 

[smokinghole]

If anyone has a Harbor Freight Tools near by they have some real inexpensive magnets that are pretty strong. $2 for a pack of 10 vs the $2 for a pack of two smaller ones at radio shack.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=67488

Also I just ended up buying a 120mm case fan for $9 at the local computer store down the street. It JUST fits in the radio shack 5x7x3 project box width wise. In fact it snaps into the lid it's so tight. I'll get a bar or two ordered soon to check out what size I want to use.

 

[jgourd]

The potentiometer doesn't work as an on/off switch. It will only vary the voltage from the DC power supply going to the fan.

And also, if you're just hooking up the pot directly to the power supply and the output (in other words, without using the LM317 circuit as shown), then you might risk burning it up if you try to put it at the fan's lowest setting. Essentially, it's trying to resist a lot, and it will get "hot!"

 

[Sagan]

Just finished my own stirplate, wanted to show what worked for me.

I decided not to use a potentiometer, and just have a single setting for my vortex. I used a 12 volt computer fan, just like everybody else. I used 2 7lb magnets from American Science and surplus. Picked up a black case and switch there. I ended up using an old lcd tv transformer and a 50 ohm 5 watt resistor I had laying around. To get the magnets away from the fan and up to the level of the outer box, I was fortunate enough to borrow the laser cutter at school and build some rings out of acrylic to mount the magnets into, it looked a lot nicer before the JB weld. JMilton1987 helped me out with the CAD files for the cutter. Also, the bar I'm using is a 2" bar.

I like the set up because it breaks down nicely and stores everything in the case.

 

[payton34]

thanks for the great directions. just finished making my stirplate by following your directions it works!! had to buy an old fan and magnet from the computer shop for 15bucks. after all parts still only 43bucks

 

[Anthony_Lopez]

Very nice! Glad to see people are still using this thread

 

[payton34]

what did you use for a stirbar? i tested my stir plate with a small screw it spun for a while then it stoped. would a comercial stir bar spin better?

 

[RegionalChaos]

Most folks are buying stir bars I believe. They will work better then a screw... I wonder though if you could use just a 2" piece of 1/4" stainless rod..

 

[smokinghole]

Well I got mine kicking. I had negligible success with power supplies left around the house. I seem to have lost some. So I had to go back a 12v and throw a resistor between the power and fan motor. It provides a little more juice than I wanted but the computer store down the street has a basket of used supplies for $10 but for some reason the 12v 500mA was $40 I asked about it and the guy at the desk was some dork that had no idea.

Anyhow I went with a two inch bar and have four magnets on each side to hold the bar. The magnets I got from harbor freight tools. All I have to do is solder everything up (only assembled with gator clips right now) and close up the box. I'll probably start using it tonight so I can get get a starter going for my Pliney clone from AHS that I'll brew on Monday.

 

[janzik]

5L flask on my stirplate that I made with a power strip that a computer monitor would sit on.

1.5L step up starter in my 3L flask. The power strip is still fully operational. I need to permanently mount my pot somewhere on the box.

 

[passedpawn]

what did you use for a stirbar? i tested my stir plate with a small screw it spun for a while then it stoped. would a comercial stir bar spin better?

Yes. Far better.

 

[MatterOne]

Most folks are buying stir bars I believe. They will work better then a screw... I wonder though if you could use just a 2" piece of 1/4" stainless rod..

You would want to use either 304 or 316 stainless, but the problem is that neither is magnetic.

 

[Catt22]

You would want to use either 304 or 316 stainless, but the problem is that neither is magnetic.

SS won't work as it's not ferrous and cannot be magnetized AFAIK. I think there are some types of SS that are somewhat magnetic, but only weakly so. Stir bars have a magnet embedded withing a Teflon casing. The magnet inside the stir bar magnetically couples with the stir plate spinning magnets. Store bought stir bars are relatively inexpensive and available in a wide variety of sizes and configurations. IMO, not worth the time and effort to make DIY stir bars. It's important to get a stir bar that matches the spacing on the stir plate magnets closely for optimum performance.

 

[slakwhere]

so i've been at it for 2 hours, and i can't for the life of me get the stir bar to stay on the bottom of my growler. i've tried all sorts of magnet configurations, hard drive magnets, harbor freight magnets. spaced off the fan center, directly on the fan center. nothing seems to work.

any suggestions?

 

[passedpawn]

so i've been at it for 2 hours, and i can't for the life of me get the stir bar to stay on the bottom of my growler. i've tried all sorts of magnet configurations, hard drive magnets, harbor freight magnets. spaced off the fan center, directly on the fan center. nothing seems to work.

any suggestions?

Get a flask.

Get a 1/2" stir bar.

 

[nicknoty]

The potentiometer won't turn the supply all the way off. If you want a slower speed, you could piggy back a second behind it.

Later,

are you able to run POTS in series? i asked a few ppl i'm friends with that had formal electronics schooling and they didn't know for sure or were playing dumb.

i haven't stirred a plate yet but the POT doesn't seem to have a wide rpm range control imo but again i haven't run it in a real world ap. yet. i'm waiting to go and get some stand off screws tomorrow to complete the build and test the functionality.

i built mine per specs of the original post except i was only able to scronge a 2" or so computer fan not a standard 4"....


side note: radio shack employee aren't that bright. also the first rocker switch i bought was bot of box failure but i soldered it and didn't check continuity between power and load prior to soldering... opps

 

[Scimmia]

Yes, you can run potentiometers in series. Your friends were either playing dumb or they paid no attention what so ever in their "electronics schooling", as it's pretty basic.

 

[nicknoty]

Yes, you can run potentiometers in series. Your friends were either playing dumb or they paid no attention what so ever in their "electronics schooling", as it's pretty basic.

thanks, good to know

 

[MatterOne]

SS won't work as it's not ferrous and cannot be magnetized AFAIK. I think there are some types of SS that are somewhat magnetic, but only weakly so.

That's basically what I said.

What I was getting at was that although there are grades of SS that ARE magnetic, either of the two types you would want to use, unfortunately, are not.

 

[Catt22]

That's basically what I said.

What I was getting at was that although there are grades of SS that ARE magnetic, either of the two types you would want to use, unfortunately, are not.

My main point was that a DIY stir bar doesn't make much sense as the manufactured ones are inexpensive and readily available off the shelf.

 

[Shag]

So, I followed the original thread exactly (at least, as far as I can tell), but I'm unable to get my fan to spin at all.

I'm using all the exact parts from the OP, a 5v Motorola wall wart, and an 80mm fan. The wall wart has two black wires, one with a dashed white line - I took the wire with the line to be positive, and the flat black to be negative. The fan has red and blue wires, so I assumed the blue to be negative.

Any idea how I can troubleshoot this? I'm not much of an electrician...

 

[passedpawn]

So, I followed the original thread exactly (at least, as far as I can tell), but I'm unable to get my fan to spin at all.

I'm using all the exact parts from the OP, a 5v Motorola wall wart, and an 80mm fan. The wall wart has two black wires, one with a dashed white line - I took the wire with the line to be positive, and the flat black to be negative. The fan has red and blue wires, so I assumed the blue to be negative.

Any idea how I can troubleshoot this? I'm not much of an electrician...

The fan should have a rating on it. I.e, voltage and current. What does it say exactly? Same for the wallwart. Try reversing the wires (briefly!).

 

[Shag]

The fan should have a rating on it. I.e, voltage and current. What does it say exactly? Same for the wallwart. Try reversing the wires (briefly!).

It's a 12VDC fan, 1.9W, .16A. I reversed the wires from the wall wart, which fired the fan right up. I guess I should have tried that. Thanks!

Doesn't seem to spin all that fast, but then again, I don't really know how fast it should spin. Won't spin at all with a magnet directly attached, so will have to add some shielding, looks like. Once I get a stir bar, I'll have to figure out if I have enough juice...

Thanks to the OP for the plans!