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

[mthompson]

-Update-

All fans are definitely not created equal. I tried a black case fan, it works on everything but the one huge HD magnet I have.....so I'll most likely use it unless I can find a 120mm.

I also tried a pci blower-style exhaust fan that I have. This thing would fling the huge HD magnet off of it.

It is only 12v and 0.16A, but is uses ball bearings and is a bit beefier....perhaps I'll use it if the other won't work through the housing.

I am planning on picking up the parts I am missing on Friday. I'll update after it gets finished.

 

[cyberbackpacker]

Since I will be scavenging an old pc tower for parts anyways, could I use the power supply from that in lieu of the cell charger type? If so, I am assuming the rheostat would then let me fine tune how much "oomph" I give the fan...

 

[Anthony_Lopez]

I haven't tried using a computer power supply. I would expect the output to be a little higher than what is required to run the fan.

Thus far, I have used:
Cell Phone Chargers, Bluetooth Headset chargers, and Linksys Modem Power Supplies.

 

[camiller]

Since I will be scavenging an old pc tower for parts anyways, could I use the power supply from that in lieu of the cell charger type? If so, I am assuming the rheostat would then let me fine tune how much "oomph" I give the fan...

If it is a very old computer it would be easy enough, if it is just old and is a ATX power supply then there are a couple pins you have to short to make it work, otherwise the power supply doesn't think it is connected to a motherboard and wont turn on.

 

[Deacon1856]

I got all the parts for this and just spent some time in the garage putting it together. Unfortunately I cannot get the fan to speed up and slow down. One speed. I've got it wired properly I believe, but the speed control is a no go. Any suggestions?

 

[Anthony_Lopez]

If you are getting voltage to your fan, and it is wired through your potentiometer, I would make sure that you have your power output or "load" from your power switch going to the center pin of your potentiometer, and the power lead from your fan going to your right pin of the potentiometer.

Please note, when I say "right pin" i'm assuming you are looking at it from the pin side and not the "knob" side

 

[DrewsBrews]

I started building one of these a while back (based on another thread) with similar parts. The only problem I noted was that the rheostat didn't seem to give much variability as far as speed control goes. For a third to half of the range of the rheostat the fan doesn't move. Turn it a little further and the fan comes on and jumps up to what appears a decent RPM, but turning it all the way only increases the fan speed maybe 15-20%. I'm not particularly electrically inclined, so I'm wondering if someone might suggest ways to correct the problem.

One thing to mention: this happened without any load on the fan. Would a stir bar in a flask full of liquid provide resistance to make the speed more controllable? I never got around to finishing it so I can't test the theory.

 

[Anthony_Lopez]

Inside a starter, there will be more resistance on the stir bar than when you try it out with water. You can go with a higher rated rheostat and try that out to see if it can give you a more variable speed. The rheostat is essentially a variable ohm resistor. Another factor is the power supply you are using. Most computer fans are rated at 12 volts DC, while most cell phone chargers are rated at 5-6 VDC.

 

[Neunelfer]

Subscribed, thanks!

 

[Anthony_Lopez]

No problem! Enjoy!

 

[Anthony_Lopez]

I posted a video as requested of the stirplate in action.

 

[Pelikan]

Hmmm...I just built up something fairly similar with an old PC fan/magnets and a 6 volt DC supply from the Shack. I paid about $20 for the power supply, and I'm really hoping it has the gusto to stir...

...if it doesn't, would replacing the fan be a viable option when compared to replacing the power supply and crapping that much cash down the drain? At this rate, it would almost have been better to just buy one.

 

[Anthony_Lopez]

It's hard to say honestly. The fan is most likely a 12 VDC pulling between .5 and 2 amps of current. A 6 VDC power supply SHOULD be able to get your vortex strong if you can play around with magnet size and the distance between your fan and your flask. With my 5 VDC power supply and the correct magnet orientation, I've had no issues getting my vortex down to the base of the flask.

 

[Pelikan]

It's hard to say honestly. The fan is most likely a 12 VDC pulling between .5 and 2 amps of current. A 6 VDC power supply SHOULD be able to get your vortex strong if you can play around with magnet size and the distance between your fan and your flask. With my 5 VDC power supply and the correct magnet orientation, I've had no issues getting my vortex down to the base of the flask.

Both distance and magnet size are limited to what I'm working with now, I'm afraid. I do have a set of four different size stir bars coming, so I'm hoping at least one of them turns well.

I did make a little stir nugget out of wire and this cheap, rubberized magnet material, and the fan spun it quite well. I just hope the fan has the torque (if that's the right word) to spin the bars.

 

[Anthony_Lopez]

If you haven't altered the power supply from radioshack, you could always return it for a 12 VDC wall wort

 

[Pelikan]

If you haven't altered the power supply from radioshack, you could always return it for a 12 VDC wall wort

Very much altered. If the 6 volt doesn't do it, I'll look around the house and see if I can find something in 9v or 12 volt. And if I can't find one I'll grind my teeth and buy another 'shack adapter.

 

[Damonic]

Very much altered. If the 6 volt doesn't do it, I'll look around the house and see if I can find something in 9v or 12 volt. And if I can't find one I'll grind my teeth and buy another 'shack adapter.

Don't do it! I GUARANTEE you know someone with a whole drawer/box/basement full of old power supplies (wall warts) that have been collecting dust because they have no idea what they go to or what they did go to was lost or thrown away long ago. Ask around, you'll find one locally for free.

 

[Anthony_Lopez]

The best wall worts I've found are from old routers or modems. They are all between 9 VDC and 12 VDC and provide plenty of current for a fan. Some of mine were so powerful that I had to throw a resistor inline to slow down the fan more than my potentiometer could.

 

[Pelikan]

Hmm...the 6v Radioshack power supply works, but at max power the vortex only extends about 2 inches down, occasionally reaching down to touch the bottom for a second, then bouncing back up. Is this good enough?

 

[planenut]

Any magnet suggestions? Shape, Size?

I've been able to get mine to work reliably with the hard drive magnets at Low to medium speeds with a 1000 ml Flask.

However, I'd like a larger container and it won't work with my 1/2 gallon milk jug or a wine carafe that has slightly thicker glass.

I bought some round and rectangular magnets from Northern Tools and they are strong but the stir bar doesn't center. It will just grab the edge of the magnet and stay put until it starts turning and then spins off.

 

[capcrnch]

Radio Shack also sells a voltage adjustable plug. I believe it goes from 6v to 12v.
Easy way to adjust your speed too.

 

[WBC]

I found the problem with the fan interacting with the magnet in the fan itself and solved the problem (The fan would not spin at full speed with the magnet mounted directly on the fan). I used a non-magnetic spacer between the fan and the magnet made from wood. I glued the wood to the fan (round 1.0 inch long) centered and then found the best mounting point (trial and error) on the wood and then permanently glued it in place. Final balancing can be done with adding a small metal nut(s) at the exact point the extra weight is needed. My fan now spins at full speed with no vibrations at all. The full magnatism is now focused on the spinning bar and it works fantastic on a 2 liter flask. I can make the vortex extend completely to the bottom of the flask.

 

[Pelikan]

Got her figured out. When I took apart the hard-drive for the magnets, there were two. I glued only one to the fan. In a last-ditch effort, I put both magnets on the fan. Now I have the 12 volt adapter on it running full tilt and it's not kicking the stir bar (w00t!). The vortex is all the way to the bottom and sending a crazy amount of bubbles through the water.

I'm a little salty about burning $15 on the 6 volt adapter that is now useless, but $30 overall for a stir plate is still about $50 in the pocket for me.

I guess my final question would be: can these things run too fast? As in, so fast the stir bar would beat up the yeasties?

 

[Anthony_Lopez]

one thick hard drive magnet centered on my fan washer worked great for me... from what I understand, keeping the starter moving is the most important part...

 

[WBC]

Got her figured out. When I took apart the hard-drive for the magnets, there were two. I glued only one to the fan. In a last-ditch effort, I put both magnets on the fan.

Yes there are 2 in each hard drive and you only use 1 of them. When the magnet is mounted on the fan if it feels like the magnetic poles are interacting with the magnets on the fan then the only way to use that fan is to put a spacer in between the fan and magnet to reduce this effect.

Now I have the 12 volt adapter on it running full tilt and it's not kicking the stir bar (w00t!). The vortex is all the way to the bottom and sending a crazy amount of bubbles through the water.

You will find it takes less voltage to do the same thing if a spacer is used. See above paragraph.

I'm a little salty about burning $15 on the 6 volt adapter that is now useless, but $30 overall for a stir plate is still about $50 in the pocket for me.

Maybe not, you will find a use for it.

I guess my final question would be: can these things run too fast?

Yes, the stir bar will get thrown off to the side a lot.

As in, so fast the stir bar would beat up the yeasties?

Not really, they are tough little guys.

 

[Pelikan]

Yes there are 2 in each hard drive and you only use 1 of them. When the magnet is mounted on the fan if it feels like the magnetic poles are interacting with the magnets on the fan then the only way to use that fan is to put a spacer in between the fan and magnet to reduce this effect.



You will find it takes less voltage to do the same thing if a spacer is used. See above paragraph.

The fan I'm using works fine without magnetic insulation. 6 volts and one magnet = Very small, 1" vortex. 9 volts and one magnet = stir bar getting thrown. 12 volts and two magnets = super-vortex right to the bottom of the flask.

In my case, it was a lack of power on two fronts: electric power to the fan and the magnetic power to hold the stir bar. Thankfully I got them both solved.

 

[tedski]

I used some nice small magnets from McMaster Carr. Part # 5862K63

 

[mthompson]

I never got mine to work right with the HD magnets I have (tried all combinations of 4 different magnets). I found some magnets at Hobby Lobby that are rated 10 on the 1-10 strength scale - although not as strong as the hard drive magnets. I bought the 1/2" (or so) ones, that came 3 to a pack. Put them on a metal washer tha't glues to the fan, two per side with opposite poles up. Easy to center this way, and spins the the stir bar pretty good.

I am gonna try a few different fans now to get one that spins faster, because I thing the hard drive magnets without the metal washer messed up the fan somehow.

The current set-up works, made a 900mL starter for my pale last weekend that got really thick with yeast. But, the vortex only goes down about 3" - I'd like at least 4" plus more speed if I need it.

Later,

 

[Pelikan]

I never got mine to work right with the HD magnets I have (tried all combinations of 4 different magnets). I found some magnets at Hobby Lobby that are rated 10 on the 1-10 strength scale - although not as strong as the hard drive magnets. I bought the 1/2" (or so) ones, that came 3 to a pack. Put them on a metal washer tha't glues to the fan, two per side with opposite poles up. Easy to center this way, and spins the the stir bar pretty good.

I am gonna try a few different fans now to get one that spins faster, because I thing the hard drive magnets without the metal washer messed up the fan somehow.

The current set-up works, made a 900mL starter for my pale last weekend that got really thick with yeast. But, the vortex only goes down about 3" - I'd like at least 4" plus more speed if I need it.

Later,

Try the drive magnets again. The key with me was using 2 HD magnets and a 12 volt power supply. It needs enough magnetic power to hold the bar in place, coupled with enough electronic power in the fan to generate torque. Your fan might be the culprit as well. I had to go through three of them before I found one that could meet the needs of this application (ended up using an Intel CPU cooling fan I had around). They need to have a fairly torquey motor.

Another thing to consider is make sure you're using the properly sized stir bar for the application. Even though this thing tears-A with the "micro" bar, it will throw the larger bars because they're not suited to the size of the HD magnets I'm using.

This thing seriously rocks now.

 

[Yunus]

I'm building one of these and something I discovered is that many of those old transformers (cell phone plugs or whatever your using) are not the voltage they claim they output. I've found them above and below ratings. The first one I tried claimed 10V but my multimeter said 15.4. I'm afraid I'll burn a fan with that.