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

[56Firedome]

Wow, Great Thread. I swear I have read this somewhere in the 90 Pages but I can't find it.
I had the fan spinning last night & I was experimenting with different Power Supplies. Today I can't get the Fan to spin at all.
I have the PS wires twisted to the Fan Black & Red wires. The fan "Twitches" but won't spin. WTF?? It worked well enough to fling 1 magnet into my Parts Bin never to be seen again... Fan only ran with 1 combo of polarity. No response the "Wrong" way.
I'm playing with 6V 800MA, 9V 900MA & 12V 1000MA Power Supplies. All 3 Power Supplies give the same result. Fan moves back & forth but won't spin. When Power is off, the Fan will spin effortlessly.
BTW, I have a 1/2" thick Plywood Spacer between the Fan & a Fender Washer, no Magnets.
Any insights would be appreciated.

 

[djii]

Try removing the magnets, you've likely de-polarized the fan motors magnets

Wow, Great Thread. I swear I have read this somewhere in the 90 Pages but I can't find it.
I had the fan spinning last night & I was experimenting with different Power Supplies. Today I can't get the Fan to spin at all.
I have the PS wires twisted to the Fan Black & Red wires. The fan "Twitches" but won't spin. WTF?? It worked well enough to fling 1 magnet into my Parts Bin never to be seen again... Fan only ran with 1 combo of polarity. No response the "Wrong" way.
I'm playing with 6V 800MA, 9V 900MA & 12V 1000MA Power Supplies. All 3 Power Supplies give the same result. Fan moves back & forth but won't spin. When Power is off, the Fan will spin effortlessly.
BTW, I have a 1/2" thick Plywood Spacer between the Fan & a Fender Washer, no Magnets.
Any insights would be appreciated.

 

[emjay]

Try removing the magnets, you've likely de-polarized the fan motors magnets

That's what I thought, but he specifically said "no magnets".

 

[djii]

no idea what you mean. if you think the fan has no no magnet, I assure you are not correct, you must have one for it to work. may not be perm, but it's a magnet.

 

[emjay]

no idea what you mean. if you think the fan has no no magnet, I assure you are not correct, you must have one for it to work. may not be perm, but it's a magnet.

No magnets mounted to the fan...

 

[djii]

oic, my bad

 

[coypoo]

I got mine working, after some serious digging I found a 5V wall wart and it spins well enough. I have to turn the rheostat to give me the the rpm possible, but I'll take it

 

[ekjohns]

I would try another fan if you have one just to try and isolate the problem

 

[56Firedome]

coypoo, I have tried a full range of Wall Warts from 3 VDC, 4.5 VDC, & 7.5 VDC as well as the 6, 9 & 12 VDC I mentioned before. All give the same result. Looks like the problem is the Fan. It's a brand new RS 4" per OP Bill of Materials.
I would return it to RS but I've removed some of the Casting which was in the way of the mounting Nuts/Washers & drilled the Holes out to allow 10-24 Bolts.
I have a 3" Fan in a Computer Case to use as a test mule. I just have to unbury it. No small Task.
Just noticed you are local. LHBS Brew Hut?

 

[56Firedome]

djii, I played with the Magnets but only after I had glued the 1/2" Spacer & Washer to the Fan. I had the same thought about de-polarizing the Motors' Magnets. The fan, on 12V, spun too fast & actually slung one of the Magnets into the Void, never to be seen again.
I got these Magnets at Hobby Lobby. $4.99 for 4. Rated 9 of 10 on the Package. But not Rare Earth Magnets.
I was trying out the different Voltage Wall Warts & 9 V seemed the best. I had them stacked 2 on a side. It's hard to tell which side is "+" & which is "-". I used the Stirbar to detiremine polarity & to place them on the Washer.
I never placed the Magnets directly on the Fan. The problem happened before I glued the Magnets to the Washer.

 

[56Firedome]

Well, What A Pi$$er!!
THe Mule works on all the Wall Warts. It's the Fan. I wouldn't be so steamed if I hadn't laid out $20 for the RS Fan. Don't see how I could take it back as I've hacked the Fan Shroud for clearance. The Mule came from my Desktop & now I have to put it back together again. Arrrgh!
It appears those Hobby Lobby Magnets are REALLY strong as they de-polarized the Motor's Magnets through the 1/2" Spacer. When I locate a replacement Fan I'll only use 1 on each side.
I'm really pissed as I got the Spacer/Washer PERFECTLY centered with no wobble. Now I have to do it all over again.
Warning to all who follow:
Really Strong Magnets can cause more trouble than they would seem to be worth. Hard to believe but appearantly true.

 

[coypoo]

coypoo,
Just noticed you are local. LHBS Brew Hut?

Yep, I live off of chambers and am pretty close to BrewHut. Love that place.

 

[mightynintendo]

Warning to all who follow:
Really Strong Magnets can cause more trouble than they would seem to be worth. Hard to believe but appearantly true.

This is good advice, though I would say that appropriate voltage is also really important. I recently made this and I discovered there is a pretty intricate interaction here between the electromagnets internal to the DC motor, the magnetic strength of mounted magnet , the stir bar magnetic strength, the size of both the stir bar and the mounted fan magnet, the voltage across the fan, the distance from the stir bar to the mounted magnet, and how well everything is centered.

Achieving the optimal balance is really quite difficult and can only be realized through some trial and error.

For instance, I have a 9V, 1A wall transformer powering a 3.5" computer case fan that is spinning two "fat" hard drive magnets (there are typically two sizes of hard drive magnets, fat and thin) stuck together.

It should be noted that the mounted magnet will slow down the fan considerably as its magnetic field interferes with the DC motor electromagnet. Too strong a magnet and you could prevent the fan from moving entirely. This can be absolved by adding a thicker spacer between the fan and the magnet, but I found that it was unnecessary in this case.

Mounting the fan too close to the stir bar creates too great a strain on the motor and it cannot move the stir bar fast enough to pull the vortex all the way down. Mounting the fan too far from the stir bar creates too weak an attraction between the magnets and the stir bar gets kicked off center.

It's tedious trying to find the perfect balance. I'm still working that out. I can easily get a full vortex on 1000 mL of water in a 2000 mL flask, but it splashes a lot and would end up coating the sides with a lot of sticky wort after 24 hours. I can't quite pull the vortex all the way to the bottom of a 1000 mL flask with 1000 mL of water with my current setup. I'm thinking probably voltage will do the trick as the magnets have proven themselves strong enough to hold the spin bar in place.

 

[ekjohns]

another piece of advice is a vortex down to the bottom is not needed for a stir plate. You really only need an inch or so. It has more to do with keeping the yeast in suspension and the surface tension disrupted to off gas

 

[mightynintendo]

another piece of advice is a vortex down to the bottom is not needed for a stir plate. You really only need an inch or so. It has more to do with keeping the yeast in suspension and the surface tension disrupted to off gas

This is truth. A vortex extending all the way to the bottom, while a great goal for "maximization," in reality increases gas exchange (the whole reason we want a stir plate in the first place) at an insignificant rate over a small dimple.

As long as you don't put an airlock on your starter (something I have seen pictures of in this thread) you're getting the job done if the starter is moving with a small dimple. Putting an airlock on your starter that is sitting on a stir plate is like clogging your toilet on purpose and then flushing. Doesn't make much sense.

 

[56Firedome]

So, Here's the question of the day:
How do I detiremine if the Fan Side Magnets are too strong?
I'd just as soon not repeat this little exercise as the Centering of the Magnet Spacer/Washer was fairly tediuos. I never got to assemble the wiring to the Off/On Switch, the Potentiometer & the Fan much less to detiremine which Voltage Wall Wart is best for my set up. I have a full array of WW's from 3 to 12 VDC with MAs from 600 to 1000.
And so it goes. Thanks for any input but I'm off to Microcenter to buy a CHEAPER replacement Fan.
Later.

 

[56Firedome]

One more thing before I buzz off to MicroCenter.
I just spoke to a buddy who just finished his Stir Plate. His 1st Starter is in the Fridge & he's very pleased with the Project.
He bought the identical Bill of Materials from RS & placed the Magnets on a Washer which was Epoxyed directly to the Fan with no Spacer. He placed the Magnets (from K & J) in pairs, Side by Side, not stacked. This allows him to use 1" as well as 2" Stir Bars without requiring repositioning the Magnets when he wants to try out different lengths.
His worked without a hitch. I suspect the K & J Magnets are at least a strong as the ones I used but since they were SxS, not stacked, the Motor Magnets were not de-polarized & all is well. A case of More is not Always Better.

 

[mightynintendo]

So, Here's the question of the day:
How do I detiremine if the Fan Side Magnets are too strong?
I'd just as soon not repeat this little exercise as the Centering of the Magnet Spacer/Washer was fairly tediuos. I never got to assemble the wiring to the Off/On Switch, the Potentiometer & the Fan much less to detiremine which Voltage Wall Wart is best for my set up. I have a full array of WW's from 3 to 12 VDC with MAs from 600 to 1000.
And so it goes. Thanks for any input but I'm off to Microcenter to buy a CHEAPER replacement Fan.
Later.

your fan side magnets are too strong if, when the magnets are mounted to the fan, the fan cannot turn fast enough to stir your starter at any distance from the stir bar.

A good way to test this would be to mount your steel washer to the fan blades (using some kind of epoxy) and then stick the magnet to the washer (DO NOT GLUE IT TO THE WASHER). Then attach your power supply directly to the fan and plug it in. If it spins without difficulty, you're probably on the right track.

The steel washer is really easy to mount in the center. The hole for the washer is very small and all you have to do is line it up with the center of the fan. Eyeball it and measure if you need.

Rare earth magnets may be too strong for this small DC motor. I don't know. Hard drive magnets are really quite ideal (except for their shape which will cause the stir bar to wobble no matter how centered it gets). With two "fat" hard drive magnets stuck together, I did not need any spacers at all beyond the 2" steel washer.

I'm using two fat hard drive magnets with a 3" computer case fan from radioshack:

12VDC Brushless Fan : Computer Fans | RadioShack.com

Of course I got the fan for free by harvesting it from the pit of old computer parts at work.

 

[mightynintendo]

One more thing before I buzz off to MicroCenter.
I just spoke to a buddy who just finished his Stir Plate. His 1st Starter is in the Fridge & he's very pleased with the Project.
He bought the identical Bill of Materials from RS & placed the Magnets on a Washer which was Epoxyed directly to the Fan with no Spacer. He placed the Magnets (from K & J) in pairs, Side by Side, not stacked. This allows him to use 1" as well as 2" Stir Bars without requiring repositioning the Magnets when he wants to try out different lengths.
His worked without a hitch. I suspect the K & J Magnets are at least a strong as the ones I used but since they were SxS, not stacked, the Motor Magnets were not de-polarized & all is well. A case of More is not Always Better.

I'm not really sure how it is possible to de-polarize a brushless dc motor with a small rare earth magnet...

 

[gingerdawg]

I'm not really sure how it is possible to de-polarize a brushless dc motor with a small rare earth magnet...

I think de-polarize is a bad term. The magnets strong field can possibly interfere with the operation of the motor.
Something I have noticed with PC fans. If the fan blades get pulled up, away from the motor, they start to run rough, or bind. The magnets could be pulling up on the fan rotor, screwing with the shaft/bushing operation. I had a PC fan (on a PC, not a stir plate) that this was a problem with. popping the fan back down in place cured the issue.

 

[ctb6760]

Just built mine tonight. Just have to get my magnets and throw 'em on. Great directions made this easy for someone with little electrical knowledge. Thanks again and can't wait to try it out.

 

[coypoo]

Happy to report mine is working well. When I actually had a starter going the 9V wall wart actually worked better. With the increased resistance the did not get thrown and I was able to get a good vortex

 

[Accidic]

I think de-polarize is a bad term. The magnets strong field can possibly interfere with the operation of the motor.
Something I have noticed with PC fans. If the fan blades get pulled up, away from the motor, they start to run rough, or bind. The magnets could be pulling up on the fan rotor, screwing with the shaft/bushing operation. I had a PC fan (on a PC, not a stir plate) that this was a problem with. popping the fan back down in place cured the issue.

On fans like that I chop the blades off then glue an extra washer on. The metal of the washer you glue the magnet to will actually help to shield the motor and prevent any issues from them. Plus an extra thickness or two of washers can position the magnets further up depending on how your box mounting is set up.

 

[56Firedome]

So, Thanks for your input but I finally solved it. As I thought all along, the problem was the Fan Motor Magnets.

The Hobby Lobby Magnets were strong enough, when stacked, to scramble the North/South Poles of the Motor Magnets causing the Motor to just twitch when power was applied.

The RS Guy tried it out on the counter with his 12V PS & his conclusion, Bad Motor. I didn't mention what I was doing with the Fan, only that it didn't work.

The next battle related to the Wiring Diagram.

The Potentiometer to Fan is on the Left, Not the Right, Connection & the Black/White Wire from the Power Supply went to the Right (non LED Side) not the Left, the Black Wire from the Power Supply & the Black Fan Wire went to the Left (LED Side) of the Power Switch.

Finally it ran. Then came the Fan Magnet height adjustment. I just cranked it up until it dragged inside the Box & then lowered it until it cleared. Approx 1/16” clearance.
I was running the 12VDC Power Supply & noticed I had No Speed Adjustment until about 2/3 of Potentiometer. I remembered that many folks on the Thread were having a problem with Speed Control & went to lower Voltage Power Supplies.

I cut the PS wire & tried 9 V. Better Speed Control but no control below ½. Then I tried the 6 V PS & had much better Control. Speed Control from 0 to Max. Slower than the 12 V or 9 V but it worked.

I tried out the Stir Bar on the Lid of the Box. The 12 V wouldn’t Spin it at all, with the 9 V it would turn about 4 times then jump off. Then I tried the 6 V & the 2” Bar spun perfectly.

Since I don’t have the 2L Flask yet I tried out a Flower Vase. At 12, 9 & 6 V the 2” Stir Bar jumped around & wouldn’t stay connected to the Fan Magnets. I noticed the bottom of the Flower Vase was Convex, domed up. Since the Bar spun fine on the Box Lid, flat, I looked around for a Flower Vase with a Flat Bottom.

I found 1 on a shelf in the Basement with a thick coat of dust. I tried it out dry & SCOOOORE! It spun like a champ. The key appears to be Flat Bottom on the Flask & the ability to accelerate the Spin Up from 0 to 100%, smoothly. The 9 & 12 V had nothing until ½ or 2/3 & then 100%. Finally, I tried it with 6 V & Water in the Vase with the 2” Stir Bar.

Holy Crap! I pulled a Vortex to the bottom of the Vase & cavitated the Stir Bar. It flew off right after that. I can run it at 75% & pull a Vortex to ¾ of the depth of the 10” tall Vase. Plenty for what’s needed for a Starter. I let it run for 12 Hrs without a problem.

Now the question is, Will it have enough power to stir when the Yeast is thick & the viscosity is high? We won’t know the answer until Monday/Tuesday. My LHBS was out of 2L Flasks & will get the next shipment then. The Vase works pretty well & holds 1L just fine. It has a wide neck which should allow O2 to get to the surface. But there’s little room if the Yeast develops a Krussen (foamy cap).

My next question has to do with the thickness of the Starter & the Neck of the Flask. So, how thick is the Starter after 2 days of stirring?

The flasks I’m looking at have a fairly small Neck. I’m wondering if the Starter would clog it up as I’m trying to pour it into the Fermenter. It would seem that NOT decanting the Starter would reduce that problem, or not. I'm figuring to Slosh it about to thin the settled slurry before pouring it into the Fermenter. I can't see how that would hurt anything. Any comments?

So, all seems to be working as advertised. I ended up swapping the Bad Fan for a New one rather than a refund, oh well, Parts for the next Stir Plate, I suppose.

 

[coypoo]

It seems that since you are pulling such a large vortex in the water that you'll be able to get one in a starter as well. You just might have to go higher on the rheostat.

As for the thickness of the starter, I seriously doubt any neck would be too small to pour liquid yeast through so you don't have to worry about that

 

[mightynintendo]

Good grief do you have to tell your entire life story?

Now the question is, Will it have enough power to stir when the Yeast is thick & the viscosity is high? We won’t know the answer until Monday/Tuesday. My LHBS was out of 2L Flasks & will get the next shipment then. The Vase works pretty well & holds 1L just fine. It has a wide neck which should allow O2 to get to the surface. But there’s little room if the Yeast develops a Krussen (foamy cap).

It's "krausen".

My next question has to do with the thickness of the Starter & the Neck of the Flask. So, how thick is the Starter after 2 days of stirring?

Have you ever made a starter before? It's not any thicker than that. It's thicker than water but it's not like you're stirring porridge.

The flasks I’m looking at have a fairly small Neck. I’m wondering if the Starter would clog it up as I’m trying to pour it into the Fermenter. It would seem that NOT decanting the Starter would reduce that problem, or not. I'm figuring to Slosh it about to thin the settled slurry before pouring it into the Fermenter. I can't see how that would hurt anything. Any comments?

You should decant your starter after cold crashing unless you like the flavor of ass in your beer. Starters, especially stirred starters, taste terrible.

 

[Mikespunchlist]

My stirrer is speed controlled with the LM317 voltage regulator. Everything stores within itself when done. The coffee container top was a little springy so I added a piece of clear acrylic on top to accommodate heavier payloads. My flask is on order so I borrowed a glass from the kitchen for testing. It should be even better with the thinner flask bottom.

 

[56Firedome]

Good grief do you have to tell your entire life story?



It's "krausen".



Have you ever made a starter before? It's not any thicker than that. It's thicker than water but it's not like you're stirring porridge.



You should decant your starter after cold crashing unless you like the flavor of ass in your beer. Starters, especially stirred starters, taste terrible.

Life Story? Not so much. But since you didn't read ANY of the descriptions of the Problem, I thought a Retelling of the issues was in order.
Oh, & thanks for the Spelling Lesson.
No, I have never made a Starter before, That was the purpose of this Project.
THanks for you input Coypoo It was helpful & not derogatory or condesending.
Later.

 

[ekjohns]

My stirrer is speed controlled with the LM317 voltage regulator. Everything stores within itself when done. The coffee container top was a little springy so I added a piece of clear acrylic on top to accommodate heavier payloads. My flask is on order so I borrowed a glass from the kitchen for testing. It should be even better with the thinner flask bottom.

that is legit! my only worry would be if the whole thing is not balanced enough it does not have much base to prevent the whole thing from toppling.

 

[mightynintendo]

Life Story? Not so much. But since you didn't read ANY of the descriptions of the Problem, I thought a Retelling of the issues was in order.
Oh, & thanks for the Spelling Lesson.
No, I have never made a Starter before, That was the purpose of this Project.
THanks for you input Coypoo It was helpful & not derogatory or condesending.
Later.

Sorry man, i didn't mean to be derogatory or condescending.