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

I just bought my Magnets! Thanks Anthony Lopez for the Tutorial and Link to the Magnets!

I got my magnets at Harbor Freight. They had a package about 10 rare-earth button magnets for something like $2 or something. Anyway, I just stacked them evenly in two stacks on the washer. Works great. If you have a Harbor Freight close to you, they also have other things you might need for a project like this.

I tried searching to no avail - what kind of epoxy do you guys use to glue the washer to the fan? Do you also glue the magnet to the washer?

And the fan I yanked from an old tower does not seem to have a lot of oomph - it spins fine and the potentiometer does make it spin faster and slower, but it can be stopped really easy by hand, is this normal? Never really messed with a computer fan before so this may be totally normal!!

Not so much diy but it was free and can be used to boil the starter.

davekippen said:

I tried searching to no avail - what kind of epoxy do you guys use to glue the washer to the fan? Do you also glue the magnet to the washer?

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i used loctite epoxy plastic. i glued 2 small rare earth magnets to the fan. the epoxy i have sets in 5 min. set it all up in an empty cigar box.

I used gel super glue

I recently rewired my Strat with a toneshaper, so I have 2 x 250 kΩ and 1 x 500 kΩ pots

can they be used for this build?

my DIY stir plate is complete and ready to be used next week! just picked up my stir bar and flask from LHBS...Great tutorial/instructions, thanks! I used a old cigar box and all I had to buy was the rocker switch, tone knob, potentiometer, quick disconnects and some screws & washer, I had the rest laying around. In total I spent about $17.00!!!

I have 4 wires coming out of the fan, white red black blue. I am assuming Red is live, blue is sensor, white is PWM, black is ground?

Going to get find a project box here at lunch yay!

I'm not sure if I messed something up or if this is normal, but on my build the rheostat gets very hot very quickly once I flip the switch. My power supply is 12 VDC 1.5A and I'm going through the lighted rocker switch (RS #275-023 which is rated at 12 VDC/ 20 A.) The fan turns and the rheostat adjusts the speed okay, but I'm concerned about this heat build up. Any feedback is appreciated!

There was a post about this earlier in the thread (or maybe it was another stir plate thread). If you have a wire connected to the center post of the rheostat it will apparently cause this. You only need connections on the two outside posts.

has anyone ever used a laptop power cord? It's the only thing I have that's 12V DC.

It has a jacket, then a metal braid, another jacket, another metal braid, then a think jacket and a hot. I don't know which metal braid is the neutral or ground, and which might just be to combat interference?

No old cell phone chargers? Old router chargers? If not you can get one at Radio Shack but not sure on the price.

i'm sure you can find a bunch of cell phone chargers at the goodwill or another thrift store

Kirch3333 said:

There was a post about this earlier in the thread (or maybe it was another stir plate thread). If you have a wire connected to the center post of the rheostat it will apparently cause this. You only need connections on the two outside posts.

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I am not an electrician, but this is incorrect. Connecting potentiometer using 2 outside posts means removing adjustable resistance and running with full resistance this potentiometer is rated at.

@mcbaumannerb
The problem may be with your potentiometer Amp rating - yours may be too low for the job so check that first - at 12VDC and average fan consumption you probably want at least 2A rating and preferably 5A (but those are pricy) to avoid heat build up and premature failure.

Having said that, this simplistic design with using potentiometer to adjust power while works OK for very low powered applications, has a major flow since potentiometer has to absorb any energy it redirects/adjusts and transform it into heat - and that's exactly what u are seeing.

In real world applications you would want to use a semiconductor e.g. transistor, teristor etc. in tandem with potentiometer where potentiometer handles small amt of Amps (low powered circuit) and therefore can have much lower Amp rating and semiconductor handles high powered circuit (fan).


And after typing all this, I find electric diagram I was describing right here on this board!
https://www.homebrewtalk.com/f51/new-stir-plate-115080/

That LM317T thingy in that diagram is what controls high-powered fan circuit and potentiometer Amp rating can now be much lower.
I'd add a heat sink to LM317t in that application.


And since we are on this topic, but I did not see anyone mention it (ok, I did not read this entire epic thread!), I'd add one more bit to stir plate design in order to let the fan expel air from enclosed box. Alternatively cut fan blades off.
This would allow for a couple of things:
1. reduce fan power consumption
2. reduce heat generated inside the enclosure and increase lifespan of a fan and components
2. allow fan to spin faster since now it is pushing free air as opposed to dead air mass trapped inside enclosure.

The way to achieve air circulation would be by

- cutting out an opening by tracing fan diameter in a top cover of enclosure,
then adding a new top plate (plexiglass with neon lights? on stand offs just above the fan to allow air to escape to the sides of the fan
- alternatively drilling a few exhaust holes right above the fan, but then you'd need to make sure those are not blocked by the flask sitting on top of them
- adding air intake hole(s) to the perimeter sides of enclosure

Now I am all fired up about building my own stir plate - was putting it off for a while but with my increased mash efficiency (around 85%) I am bound to do this sooner rather than later.

Or make it really easy and forget the speed knob, just find an adapter that works right. For mine it's the 12 volt. Or get one at radio shack that has a switches to change the voltage.

Thanks for the follow-up Kirch3333 & vash68. I did try it on the outside posts and discovered that indeed the fan ran at full capacity. Putting the input line on the 1st post and the fan line on the 2nd got it working without getting excessively hot. I too was concerned about build-up of heat and or air inside a box, so I re-designed mine to a more open concept:


I used a piece of scrap plexiglass and some bolts for legs. Now that I have the overheating issue fixed it seems all set to go - should be able to put it to a real test in a couple of weeks when I brew next.

Thanks again!

This looks awesome!
Watch out for spills though, maybe add a skirt to a switch/potentiometer side?

I'm going to set the flask in a glass pie plate to catch any erupting krausen

Made this last night per OP instructions and parts list.

Picking up stir bar later today to take for test drive, but so far, everything seems to be working-just need to get the magnets dialed in now.

Thanks to the OP for making this available!!

I also want to thank Mysticmead for pointing me to this thread.

Thanks to the OP for posting this. Made mine per instructions last night. Runs like a champ. Many future generations of yeast thank you.

For those wondering, I used 5V power supply with a 12 volt 80mm case fan. Thing works like a charmed.

Had a gallon of water spinning perfect, but now that I have an actual starter on it the thing is being a pita! Go figure! I know the problem is that my jug doesn't have a flat bottom, but I don't have a flask yet. Guess I better get one ordered.

TBaGZ said:

Had a gallon of water spinning perfect, but now that I have an actual starter on it the thing is being a pita! Go figure! I know the problem is that my jug doesn't have a flat bottom, but I don't have a flask yet. Guess I better get one ordered.

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Either drop the voltage of your power supply or look to add a resistor some to the fan positive wire. It could be spinning to fast.

It's because the bottom of this gallon jug isn't flat.

I have some questions for you guys. First ill say I have a bare bones education of wiring. I've installed a few lights and recepticals but that's the extent of my experience.

Anyway I picked up all the equipment for this project and started putting together last night. I picked up a 12v DC computer fan, and used my old razor charger which has a 6.5v dc output. I had it all wired up accordingly but it didn't move an inch when plugged in.

I took it apart (those dam connects cost a lot) and tried wiring it straight forward. White charger wire to red comp fan, and black to black. Nothing.

So I stripped a USB cable charger that I had laying around and hooked up the red wire to the red wire and computer fan and black wire to black wire. The other cables I left alone (green,white, and uninsulated). Then it moved. But with the magnet on top I have to spin it so it can start itself.

I hope you can tell me what I'm doing wrong.

Thanks in advance!

Mojzis said:

I have some questions for you guys. First ill say I have a bare bones education of wiring. I've installed a few lights and recepticals but that's the extent of my experience.

Anyway I picked up all the equipment for this project and started putting together last night. I picked up a 12v DC computer fan, and used my old razor charger which has a 6.5v dc output. I had it all wired up accordingly but it didn't move an inch when plugged in.

I took it apart (those dam connects cost a lot) and tried wiring it straight forward. White charger wire to red comp fan, and black to black. Nothing.

So I stripped a USB cable charger that I had laying around and hooked up the red wire to the red wire and computer fan and black wire to black wire. The other cables I left alone (green,white, and uninsulated). Then it moved. But with the magnet on top I have to spin it so it can start itself.

I hope you can tell me what I'm doing wrong.

Thanks in advance!

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The magnet will keep the computer fan from moving if you place right on it. Glue a big metal washer to the fan hub (needs to be centered well) and then the magnets on it. Can use something not metal instead of a washer but then would have to glue the magnet to it. I need a 12 volt charger get my stir bar going, but depends on a lot of variables. Test for balance or the fan will burn out quick.

I picked up the washer this morning. I didn't have it while wiring and I did put the magnet right on the fan.

What do you mean test for balance? Make sure the magnet is balanced on the fan?

I also bought a 2" stir bar. I hope it's not too big.

Mojzis said:

I picked up the washer this morning. I didn't have it while wiring and I did put the magnet right on the fan.

What do you mean test for balance? Make sure the magnet is balanced on the fan?

I also bought a 2" stir bar. I hope it's not too big.

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Make sure the washer is glued exactly on the center of the fan, and the magnet is stuck note center of the washer. If they are not the fan will wobble. Will burn out the fan motor fast. Use some glue that doesn't dry quickly, put it on and slowly turn fan until it looks centered. Then plug in and you will see if its balanced. If not adjust. Magnet is easier because you just move around. You want the fan to spin without wobbling.

I got it all glued down and set up. I got the 5.6v charger to work but it doesn't want to spin the bar. The washer is pretty thick and the magnet is 50 x 10 x 5mm. Maybe its too much weight? Would a higher voltage power source give it extra power to get the 2" bar moving or do I just have too large of a stir bar?

Also my fan is a cheap 2$ fan off ebay, maybe its too sh***y?

Sorry for the continuing questions, but this thing is frustrating.

Mojzis said:

I got it all glued down and set up. I got the 5.6v charger to work but it doesn't want to spin the bar. The washer is pretty thick and the magnet is 50 x 10 x 5mm. Maybe its too much weight? Would a higher voltage power source give it extra power to get the 2" bar moving or do I just have too large of a stir bar?

Also my fan is a cheap 2$ fan off ebay, maybe its too sh***y?

Sorry for the continuing questions, but this thing is frustrating.

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I can't get my 2 inch bar to spin right with even a 12 volt but my 1 inch one spins perfect with the 12v. Best design is prob a 12v with a potentiometer to slow it down if needed. My design is a cigar box, I think the amt and type of material between the magnet and glass determines a lot. Bottom line every DIY version of a stir plate acts diff and you have to tweak and test

I might turn my 1st gen mac mini into a stir plate.

Mojzis said:

I got it all glued down and set up. I got the 5.6v charger to work but it doesn't want to spin the bar. The washer is pretty thick and the magnet is 50 x 10 x 5mm. Maybe its too much weight? Would a higher voltage power source give it extra power to get the 2" bar moving or do I just have too large of a stir bar?

Also my fan is a cheap 2$ fan off ebay, maybe its too sh***y?

Sorry for the continuing questions, but this thing is frustrating.

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I found that most cell phone chargers have a much lower current rating that the fans we are trying to power. I started off with a 5V 200mA charger and it spun my fan, but not very fast and definitely not reliable with a starter. My current setup uses a 5V 1000 mA charger and it spins the fan fast enough that it is functional, but it still spins nowhere near as fast (even without the magnet) as it did when it was in a computer. I don't remember the current rating of the fan offhand, but between the voltage and current the charger is well below the fan's values. Ideally, if the charger's output specifications match the fan's input specifications you will get the best performance. In this case though I don't recommend running it without a pot for speed control.

A friend gave me a 120 mm 12v fan and a 12v power supply they had laying around. Re-did the whole thing and the fan if ridiculously fast now, so that's good. However I haven't got the damn bar to move. I ordered some more magnets online to see if my magnet I have isn't the right shape. I'd hate to spend the 6$ for a one inch bar instead of my 2".

Mojzis said:

A friend gave me a 120 mm 12v fan and a 12v power supply they had laying around. Re-did the whole thing and the fan if ridiculously fast now, so that's good. However I haven't got the damn bar to move. I ordered some more magnets online to see if my magnet I have isn't the right shape. I'd hate to spend the 6$ for a one inch bar instead of my 2".

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Do you have a potentiometer installed? It sounds like the fan moves too fast for the magnetic fields between the magnet and the stir bar to remain coupled. I find it best to turn it on with the potentiometer set to min speed and then slowly speed it up. Eventually you will find a speed that will throw the bar.

Yeah the pot's installed, but it still goes pretty fast. However it wont throw the magnet even turned all the way up. I hope its not too fast now....

Edit: just switched the supply back to 5.6v and the bar moves a little more. Maybe the pot doesn't slow the 12v down enough? Maybe I need a bigger pot to use the bigger supply...

I found success in computer fan, washer, hard drive magnets, cigar box and 12v adapter with 1" bar. It spins perfect with a 2L flask and after centering the washer and magnets its almost silent. Perfect vortex, and I didn't have to buy one thing. I tried 6, 9, and 12 volt adapters and the 9 spun it but the 12 is better. Point is you can do this without buying a pot and doing that wiring if you have a variety of adapters laying around, just have to find the right combo.

I'm using 4 hard drive magnets from 2 old hard drives and man are they strong.

I thought I had an old hard drive to harvest from but I lost it somewhere.

I got the bar to spin with the 6v, pretty good vortex. I don't have the flask so my growler will work for now. I just cant turn it all the way up because it will slide off the curved bottom. Oh well, it works. Maybe when I get a flat bottomed flash i'll hook the 12v up again.

Thanks guys for your help/advice.

Here is mine.
I bought the Radio Shack rheostat and knob and tested it by squeezing my 3" square fan into a round cheese container. Perfect fit! Who needs an $8.00 project box and machine screws?

OK. Its a POS. But it works great! Can't wait to make my first starter.

replaced the electronics in my guitar, wondering if a 250kΩ potentiometer will work instead of the 25Ω listed in the OP?