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Well I tried this out and after several days still am unable to get it working. I managed to get everything on the list at the start from RS and a 12v fan, 9v charger and 2 of the curved HD rare earth magnets. After getting the wiring set up so the fan works, is adjustable and the power is operable I decided to give it a go. The washer I used was the biggest they had at 1.5".

Using two magnets in an "S" pattern or one on each rim of the washer would not spin the bar. This was the case regardless of how far I moved the flask away from the fan or speed. Also, even if the plastic lid was between the fan and flask the bar would not spin.

One of the magnets broke now too so that is scrap. I am not sure where to go from here. Ideas anyone?
 
T2P said:
Well I tried this out and after several days still am unable to get it working. I managed to get everything on the list at the start from RS and a 12v fan, 9v charger and 2 of the curved HD rare earth magnets. After getting the wiring set up so the fan works, is adjustable and the power is operable I decided to give it a go. The washer I used was the biggest they had at 1.5".

Using two magnets in an "S" pattern or one on each rim of the washer would not spin the bar. This was the case regardless of how far I moved the flask away from the fan or speed. Also, even if the plastic lid was between the fan and flask the bar would not spin.

One of the magnets broke now too so that is scrap. I am not sure where to go from here. Ideas anyone?
Click to expand...

What is the size of your stir bar? Try one magnet, put the bar on the magnet to find where it lines up and center at that point:
IMG_4424.JPG
 
T2P said:
It is a 2 inch stir bar.
Click to expand...

A lot of people have problems with longer stir bars. Still try the single magnet. I think trying to use two of the hard drive magnets gets real finicky because the axis of magnetization tends to be a straight line through the long axis. Using two of them in any configuration might work sometimes but you have to make sure you know which poll is where. Otherwise, get some small button sized magnets where the face of the magnet is one poll or the other.
 
Power problem? I have a 5V phone charger and a 12V computer fan. I can't seem to get it to spin the fan at all. When I take the fan and attach the red and black to a 9v battery it practically wants to fly off the table. The phone charger also has a thing white wire on it that I am guessing is the ground. Is it necessary to get it to power the fan? Please help... must get starter going this week! Alt bier is in the works.
 
...furthermore when I get the fan powered up with the battery and rheostat I can't get the stir bar to do much more then jump around and never actually spin. How can something so simple be so frustrating. I must be a dolt! Thanks for the help!

I also checked and my rheostat is a 10ohm jobber because I thought that was what someone else on here had. Will it make that big of a diff on this project from the 25ohm unit?
 
Ok so this is what I did. I went ahead and dropped the stir bar on the magnet and marked where the center of the bar met up with the magnet. I then put the magnet on the fan so the mark matched the center of the fan. After putting the assembly the bar appears to be getting thrown off of the magnet and basically sits at the outside edge of the field jitterbugging around. I found that if I turn the dial down all the way and then turn on the power, if the bar is above the fan/magnet, the fan will not start spinning. Turning the dial all the way up from the start makes it spin with the magnet on.

Is it possible that the washer I have is interfering because it has a fairly large hole in the center? It is a 1.5 diameter washer with 0.5 to 0.75 inches open in the center.

When you talk about the button sized magnets can they be black ceramic ones from home depot or something or do they have to be rare earth ones? I went to radioshack and all they had for rare earth were ones the size of a pencil eraser. The guy at the counter said they were regulated or something because they can wipe hard drives but that sounds like bunk to me.
 
Last update with some new progress. I think I have been able to get the magnet to at least stay in the center and possibly spin. It is not enough to create any vortex though, just some bubbles on the surface of the starter in the very center.

The axis of the HD magnet was about 2/3 towards one side of the length of the magnet so in order for it to be balanced I added a small nut right next to the magnet. I also brought the fan as close to the underside of the plate as possible but still no luck for the vortex.

Is the magnet too weak? Is the fact that I had to add the nut to balance it out slowing the fan too much possibly?

Ideas for where to go now?
 
Any thoughts on my power supply questions above?
- 9 Volt battery makes the fan want to fly off the table and the two chargers I have tried won't do anything.
- Will a 10ohm potentiometer work or does it have to be a 25ohm?
- Is it better to have the potentiometer wired to increase power or decrease power

Thanks all, I am hoping to get this figured out in time for a starter this week.
 
AlchemyBrewing said:
Any thoughts on my power supply questions above?
- 9 Volt battery makes the fan want to fly off the table and the two chargers I have tried won't do anything.
- Will a 10ohm potentiometer work or does it have to be a 25ohm?
- Is it better to have the potentiometer wired to increase power or decrease power

Thanks all, I am hoping to get this figured out in time for a starter this week.
Click to expand...

I can't advise on the power supply as I use AC fans on mine, but if you don't happen to get it up and running in time, I would just go ahead and make the starter anyway. You can propagate the yeast nearly as well without a stir plate. It's just requires a little more time. Give the flask a swirl now and then. Don't shake the flask vigorously as this can cause it to go volcanic on you in a flash. Swirl it as often as you conveniently can for best results. Aerate the starter wort with pure O2 before you add the yeast if you can.
 
What size potentiometer do you use on your AC fan? I think I have an AC fan laying around but I know that it will go way to fast with out a control dial. Thanks
 
AlchemyBrewing said:
What size potentiometer do you use on your AC fan? I think I have an AC fan laying around but I know that it will go way to fast with out a control dial. Thanks
Click to expand...

I use an ordinary rotary type light dimmer in lieu of a potentiometer. I've built about 20 sitr plates for my brewing buddies using this configurattion with very few problems and those have been easy to resolve.
 
I've started adding the potentiometer and on/off switch to my stir plate. I used an aquarium fan that is 12V. Unfortunately the wires are both black so I have no idea which is positive and which is ground. I have a multimeter, can I use this to test which wire is which? I have only used it to test batteries, so want to make sure what I am doing is correct if I use it with electrical current.
 
Most DC motors are not polarized, reversing the polarity (positive and negative) just changes the direction of the motors spin. For your purposes it's irrelevant.
 
I struggled with this biuld for 5 days!!! I had the familiar problem of the stirbar being thrown all over the place, not centering and basiacally not spinning at all. I have finally solved my problem and figured I would post what I had to do here in hopes it will help someone else.

My initail setup consisted on a 120mm case fan, 1x 2" steel washer glued to the fan hub, 1x hard drive magnet (centered) and a 12v adapter, rheostat, rocker switch, etc. (like the build here)...no joy.

I tried 2x HD magnets opposite of each other...no joy.

I tried the 2x HD magnets on top of each other and centered...no joy.

I tried 3x HD magnets on top of each other and centered...no joy.

I tried 4x HD magnets opposite of each other (2x on each side)...no joy.

I was ready to give up. Why is this so hard. It just didn't make any sense to me. Then I read that you need to make sure that if you use HD magnets opposite of each other, they need to be polar opposites...north side up on one, south side up on the other. I was sure this woudl solve my problem.

I tried 2x HD magnets opposite of each other and ensured that they were magnetically opposed...no joy.

:mad::(:mad::(

Ready to give up again but then my Irish rage kicked in. There was no way in hell I was going to let this beat me!!!

I read in another thread that 12vdc may be too much power...causing the fan to spin too fast too soon. I dug around in my basement and found a selectable voltage adapter (1.5v thru 12v). I started at 1.5v with 2x magnets opposite each other.

When I got to 4.5v and 2x magnets on opposite sides...I actually got the stirbar to spin. However, after about 5 seconds, it would get thrown off. Regardless, I considered this a mild success.

I continued to play with voltage and magnet combinations and never got any closer.

Then...while fiddling with the magnets (sicne they love to get stuck together) I accidentally broke on in half. Hmmmm...could it be?

I tried 2x 1/2 magnet on opposite sides at 4.5v...JOY!!!! I could get the stirbar to spin and not be thrown.

In the end, I found the best combination for me was 1/2 HD magnet on each side and 6v. This will get me about 1/2 vortex from top to bottom. If I slowly take the rheostat up to about 3/4 power, I can get a complete vortex from top to bottom and running smoothly. Once I start to go past the 3/4 mark, the stirbar begins to rattle (as you will hear in the video). I just back it off a bit and it is happy once again.



I guess the moral of the story is that the HD magnets are too strong, or, are too close together when used whole (either a strength or interference problem). Of course, I will need to fine tune a bit once I do my first starter sicne this was only done with water, but I feel confident that everything will work as expected.

One final note: the flask that I "borrowed" from work does nto have a perfectly flat bottom...it is a little convex (but not as much as a drinking glass). This of course in not ideal and I still had good results. However, I think I will go "shopping" for one with a flat bottom. ;)

Thank you for posting this how-to and I can now pick up my clumps of hair off of thr floor and glue them back to my head. :cross:

John
 
Last edited by a moderator:
johnodon said:
I struggled with this biuld for 5 days!!!
...
I guess the moral of the story is that the HD magnets are too strong, or, are too close together when used whole (either a strength or interference problem). Of course, I will need to fine tune a bit once I do my first starter sicne this was only done with water, but I feel confident that everything will work as expected.

One final note: the flask that I "borrowed" from work does nto have a perfectly flat bottom...it is a little convex (but not as much as a drinking glass). This of course in not ideal and I still had good results. However, I think I will go "shopping" for one with a flat bottom. ;)

Thank you for posting this how-to and I can now pick up my clumps of hair off of thr floor and glue them back to my head. :cross:

John
Click to expand...

The poles of a hard drive magnet are not on the face of the magnet, but usually through the long axis. I suspect that one magnet centered properly at a lower speed would have worked for you, the full 12 volt speed of the fan was your only real problem. The best way to find the magnetic center of a HD magnet is to simply attach your stirbar to it and mark where it centers, then line that spot up with the center of the fan. See the red dot on mine:

IMG_4424.JPG
 
I tried every combination of 1, 2, 3 and 4 magnets and 1.5v thru 12v. Either the fan would not turn or the stirbar would get thrown. It wasn't until I broke a single magnet in half that I had any success.
 
Just finished building this, and it's a no go. The stirbar just rolls, instead of spinning. I'm guessing it's the 12 v PS, so I'm going to just cut it off and splice a 6 volt onto it. we'll see if that works.
 
nice, the 6 v won't spin the fan and i found a 9 v, and that one just makes it roll too. The magnet is centered perfectly on the fan. Could it be too weak? i knew this wasn't gonna be as easy as turn it on and watch it work.
 
Need more details, what type magnet(hard drive, buttons, etc. and rare earth of conventional material)?, length of stirbar?, a picture wouldn't hurt. How close is the magnet to the top of your enclosure? What type of enclosure? How thick is the top?

I have to be leaving for home after I post this but I'll check back in a half hour or so.
 
It's made out of the exact parts list on page one. I used a single hard drive magnet that's perfectly centered on the fan. I built it the same exact way that this thread describes. I'm using a 1 inch stir bar. I'm thinking maybe the stir bar is too small, or light.
 
if I put it on top of the enclosure, it'll spin perfectly. What I'm using for a "flask" is a small wine decanter. It seems like the center of the decanter is concave ( i think that's the right word). The stir bar will spin, on low speed, till it gets up to speed. Once it gets there, it gets thrown. I tried it in a flat bottomed glass, and it threw it as well.
 
finally got this working. I had to turn the screws around and get the magnet as close to the top of the enclosure as possible. I even took pics.



The 2.5 inches was too short, so I backed it out and double nutted.



The screws from the bottom of the AL plate.



Proof that it works.....and it works at how or high speed.



Just a shot of the inside wiring. Hopefully someone will see this and ask if I'd come and autograph their stir plate.



My overglued magnet.

So I think the key here was that the magnet be as close to the enclosure without touching it. Maybe the OP used stronger magnets, so his worked this way, but mine needed a slight tweaking. Anyway, it works, thanks for for the informative write up, and for any others' help
 
mikeysab said:
finally got this working. I had to turn the screws around and get the magnet as close to the top of the enclosure as possible. ...
Click to expand...

Glad you got it working, that is kind of the direction I was heading with my questions yesterday. I did notice with mine that if I was too far away from the top OR to close to the top I had issues, I kind of had to find the sweet spot as far as distance from the top of the enclosure goes.
 
Wow... I can't believe this is still active... glad to hear that everyone is still enjoying the post. There is definitely some fine tuning to be done, however if you work on this, it will work perfectly... I'm still using the original from this build without issues.
 
SOOO I just built this but its not ready I mean all the electronics are good but I have a laptop HD magnet will this be a proper magnet or do I need to get something else?
 
johnodon said:
I tried every combination of 1, 2, 3 and 4 magnets and 1.5v thru 12v. Either the fan would not turn or the stirbar would get thrown. It wasn't until I broke a single magnet in half that I had any success.
Click to expand...
johnodon I had the same issue when designing my stirplate and it was finally resolved by increasing the space between the face of the hard drive magnet and the top of the box that the flask sits on. I actually hot glued a 6 inch long piece of 1 x 3/4 pine to the box lid and then hot glued the fan to the piece of wood and this did the trick.
 
Something to keep in mind for everyone doing this project, if your using a hard drive magnet the center of the magnetic field may not be the physical center of the magnet, find where your stir bar lines up and mark the center point, then line that up with the center of your fan. Also, I had kind of assumed that the magnet would be strong enough to hold itself to the washer I glued to the fan but with my first starter by about the 36 hour mark the magnet had shifted slightly and had started throwing the bar. I ended up hot gluing the magnet down after I got it lined back up.
 
That is correct. The washer is meant for fine tuning the position of your magnet BEFORE gluing the magnet down.
 
First of all, thanks to the OP for the superb write-up. I followed the build with a slight twist and incorporated the stir plate into the lid of a rubbermaid container (my project box) that I'm going to use to store my yeast starter equipment.

Here is a shot of it in storage mode...

DSCN1707.JPG


And here is a shot of it in action...

DSCN1711.JPG


The only modifications included having to purchase Neodymium magnets (3/8" dia. w/5lb pull force) and cutting the 2 1/2" bolts to length. I wasn't patient enough to source a HD magnet, but I had immediate success with the route I took. Oh, and I went with a black knob instead of the silver.

FWIW, I haven't epoxied the magnets to the washer yet, but I haven't experienced any movement during testing. I plan on a full scale test for an upcoming Black IPA or Foreign Extra Stout.
 
Just wanted to say thanks for this write up. I made my stir plate awhile ago, but just snapped a pic of it and wanted to show it. Thanks for the Idea.

 
I was thinking of going the same route with the power plug. Did you re-purpose something that you had on hand, or did you pick something up from Radio Shack?
 
I did the same thing to my other stirplate. I found that Linksys router power supplies work quite well. I took it to radioshack and found the mating socket. I'll update this to show both setups at some point.
 
OK does the vortex need to go to the bottom for this to be a success? I mean will I still make good starters out of this by having the vortex go 3/4 of the way down ?
 

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