Homemade Yeast Stir Plate

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jdetechguy
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Homemade Yeast Stir Plate

Post by jdetechguy »

I have been reading a lot about yeast lately and decided to start a small yeast lab for my brewing and distilling projects. All labs need a stir plate. In the spirit of the forum, I decided to make my own instead of buying one. I realize this is a rather simple project, but might motivate others

So, I strolled on down to Radio Shack and bought the parts. I could have bought a new one for $40. This one cost $30, but could be built for $15 if you are patient and order parts online or scrap out your own project box. I had the following:

- Hard drive magnet
- Computer fan
- Ehrlenmeyer flask
- Stir bug
- 12 volt DC power pack

I purchased the following:

- Plastic project box
- On/off switch
- Potentiometer
- Pot dial switch
- Stick on rubber feet

I drilled the holes for the switch, power cord and potentiometer. I then wired and soldered everything. The only trick was how to mount the fan. I used hot melt glue to install the magnet on the fan. I put 4 small stick on feet to each corner of the fan. I located the center of the top of the project box and glued the fan to the lid. The feet gave enough clearance for the fan to spin with the magnet attached. I only put glue on the rubber feet.

I closed things up and gave it a try. It worked, except the potentiometer worked in reverse. As the pot has 3 connections, I just moved the outer wire to the other side. It worked fine then.
I then put 4 large rubber feet on the bottom to keep it from sliding around.

Here are the pictures:
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20161210_201952-600x800.jpg

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Re: Homemade Yeast Stir Plate

Post by Bushman »

I tried building one a year or so ago with not a lot of success. I just couldn't get it to work consistantly.
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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

I had to reposition the magnet a couple of times. I have to make sure the bug is locked in before starting the fan. Otherwise it just bounces around.

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Re: Homemade Yeast Stir Plate

Post by der wo »

I also build a stir plate just right now.
Not only for yeast, more for a bit experimenting with oxidation of spirits.

I also will use a pc ventilator. But I will use two magnets in a row with opposite polarity, like here:
http://www.experimentalchemie.de/versuch-057.htm" onclick="window.open(this.href);return false;" rel="nofollow

But I am waiting for a small parcel from China with a few stir magnets (ptfe ones). I hope it arrives in January.
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Re: Homemade Yeast Stir Plate

Post by Danespirit »

That's a nice idea.
I thought about a similar setup.
The difference would be mine runs with a motor, that has a nylon disk attached where the magnets are.
I have an SCR lying around, it would serve as a step less rpm regulator.
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Re: Homemade Yeast Stir Plate

Post by der wo »

SCR or potentiometer all the same there will be the problem, that you cannot control such a motor down to a very low rotation. It only can turn fast or it doesn't turn at all. This is a problem when starting the stirrer, because the stirring fish will loose the magnetic contact when started too fast.

My motor needs 0.35A / 4.2W at 12V. It has 34 Ohm. So simple controlled with a potentiometer, the poti should be able to handle 4.2W. At least in the full speed setting (0 Ohm). A poti for 4.2kW is very expensive. If I don't need the full speed I could connect a resistor before and then a smaller poti is ok.
So I think a SCR is way better, but just for experimenting a potentiometer will be ok.

Or you decide for a maximum speed and fix it with a simple resistor (with appropriate wattage!) or use for example 10 instead of 12V, and do a "manual start", you block the motor with a hand, switch on and slowly let start it turning.


@jdetechguy
How much Ohm do you recommend for the potentiometer?
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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

Der Woo. I have to tweak it. Radio Shack only had a 10Kohm pot. I am getting too much speed on the low end. I need some resistance. The way I get around the bug spinning, is by making sure the magnet engages the bug before turning on. I did not do the electronic math ahead of time, as I am not good with that. But, I need to, since I have too much speed. I thought about dropping down to a 9volt DC adapter. I started with 6 volt DC and that was too weak. My fan is not that powerful.

Thank

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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

I used an audio pot. Here it is. Its overkill. I ordered 5 of the Chinese PTFE stir bugs too.

https://www.radioshack.com/products/10k ... oCMB7w_wcB" onclick="window.open(this.href);return false;" rel="nofollow

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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

der wo wrote:I also build a stir plate just right now.
Not only for yeast, more for a bit experimenting with oxidation of spirits.

I also will use a pc ventilator. But I will use two magnets in a row with opposite polarity, like here:
http://www.experimentalchemie.de/versuch-057.htm" onclick="window.open(this.href);return false;" rel="nofollow

But I am waiting for a small parcel from China with a few stir magnets (ptfe ones). I hope it arrives in January.
I actually broke my magnet in half and glued 1 piece to each end. Effectively giving me 2 magnets of opposite polarity. Before I did that, I could not get the fish bug to engage at all.

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Re: Homemade Yeast Stir Plate

Post by der wo »

That the switch of the poti can handle 3A at 30V does not mean that the poti can it too. After a while the grinding contact (if it is the right word for this) will go black. If it stops working properly sometimes, you know why.
And 10 kOhm? I thought about using 100 Ohm. Do you can use the whole turn of it?
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Re: Homemade Yeast Stir Plate

Post by der wo »

jdetechguy wrote:I started with 6 volt DC and that was too weak. My fan is not that powerful.
Too weak means it didn't start to turn?
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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

Correct, the fan would run slowly on its own, but did not have enough strength to spin the fish.

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Re: Homemade Yeast Stir Plate

Post by rgreen2002 »

That's some nice work jd. I built exactly the same thing and I think the total came out to between $25-30 as well. I started with a 5K Ohm pot from Radio Shack too but it was getting way too hot for my comfort! Don't ask me to do the math because I just woke up and it is far too early on a day off for that but I figured out after I bought it that it was under powered (the heat told me that too :mrgreen: )

I went with a PWM instead and the cost difference was not too bad. I got this little guy:
Pulse-Width-Modulator
Pulse-Width-Modulator
Found it here: https://www.amazon.com/gp/product/B00RY ... UTF8&psc=1" onclick="window.open(this.href);return false;" rel="nofollow

I did the 12v DC fan and NdFeB magnets as well. Wired up with a wall wart power supply I had lying around.
Stir plate
Stir plate
She is actually running quietly in the background now getting ready to do her part in the next bourbon batch!
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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

Thanks RG. I will look into making that mod. The funny thing is that I bought my son one from a store versus making him one.

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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

RG, I like the PWM idea. I just ordered one. Thanks for the idea and link.

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Re: Homemade Yeast Stir Plate

Post by ShineRunner »

I made mine out of an old useless PC power supply. It already has a fan, case and 12V power supply included! I just had to glue the magnets to the fan and cut all the unused wires out. Added a cheap potentiometer from radio shack.. The flask sits right on top of the fan cage and works great! The distance between the flask and the magnets is a touch too much, so it takes some fiddling around to get the stir bar to catch, but once it does- it's solid.

SR
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Re: Homemade Yeast Stir Plate

Post by Bushman »

der wo wrote:I also build a stir plate just right now.
Not only for yeast, more for a bit experimenting with oxidation of spirits.

I also will use a pc ventilator. But I will use two magnets in a row with opposite polarity, like here:
http://www.experimentalchemie.de/versuch-057.htm" onclick="window.open(this.href);return false;" rel="nofollow

But I am waiting for a small parcel from China with a few stir magnets (ptfe ones). I hope it arrives in January.
I might have to translate that link looks interesting, and I might have to get back to this project.
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Re: Homemade Yeast Stir Plate

Post by der wo »

There are so many diy instructions, you will find enough in English. Google and youtube. Either pc fans, hard drives or cd players, either two round magnets or one magnet from a hard drive.

Here an English video with a few interesting details:
https://www.youtube.com/watch?v=twwjZP8wrqs" onclick="window.open(this.href);return false;" rel="nofollow
-He shows how to position the two magnets best for a given stirring bug.
-and a simple electronic circuit without overpowering the potentiometer.
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Re: Homemade Yeast Stir Plate

Post by Bushman »

Thanks, I think the one I tried to build was from a member on another forum.
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Re: Homemade Yeast Stir Plate

Post by rgreen2002 »

ShineRunner wrote:I made mine out of an old useless PC power supply. It already has a fan, case and 12V power supply included! I just had to glue the magnets to the fan and cut all the unused wires out. Added a cheap potentiometer from radio shack.. The flask sits right on top of the fan cage and works great! The distance between the flask and the magnets is a touch too much, so it takes some fiddling around to get the stir bar to catch, but once it does- it's solid.

SR
SR...the same here. Inside the "box" I hot glued the power supply to the side of the box where I had drilled out a spot for the plug.
Plug.jpg
I like the "fan cage idea".... wish I thought of it. I bought long screws to adjust the height of the fan from the bottom of the plate. I then countersunk the screws on the plate so they would not interfere with the flask when it sits on the plate
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Re: Homemade Yeast Stir Plate

Post by jdetechguy »

I like the fan cage idea too. That fan probably has a little more power too.

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Re: Homemade Yeast Stir Plate

Post by Brutal »

Nice thread. This kind of thing is not usually discussed here. I just want to add that there are pc case fans that are specifically made for use with pwm. Most are not made for it but might still work.
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Re: Homemade Yeast Stir Plate

Post by der wo »

Good info about professional magnetic stirrers in English:
http://www.bola.de/en/technical-informa ... rring.html" onclick="window.open(this.href);return false;" rel="nofollow

And stirring bars:
http://www.bola.de/en/technical-informa ... -bars.html" onclick="window.open(this.href);return false;" rel="nofollow
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Re: Homemade Yeast Stir Plate

Post by rgreen2002 »

With a big enough motor/magnet/stir bar.... what would it take to drop this into my 55 gallon mash tank.... :think:
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Re: Homemade Yeast Stir Plate

Post by Danespirit »

Bushman wrote:
der wo wrote:I also build a stir plate just right now.
Not only for yeast, more for a bit experimenting with oxidation of spirits.

I also will use a pc ventilator. But I will use two magnets in a row with opposite polarity, like here:
http://www.experimentalchemie.de/versuch-057.htm" onclick="window.open(this.href);return false;" rel="nofollow

But I am waiting for a small parcel from China with a few stir magnets (ptfe ones). I hope it arrives in January.
I might have to translate that link looks interesting, and I might have to get back to this project.
Bushman, at the bottom of the page there is an option for an English translation.
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Re: Homemade Yeast Stir Plate

Post by der wo »

Results about my magnetic stirrer:

The cheap chinese magnetic bugs you can buy on ebay are shit quality. The magnets in the ptfe are very weak. Ptfe is cheap, magnets are expensive...
s-l500.jpg
But it works very well, if the magnets on the motor are very strong.

The neodymium magnets are diameter 2cm, heigth 6mm. Glued on the motor with opposite magnetic direction.
The motor is 12x12cm, 12V, 4.2W. 2000 rpm, but with the magnets probably much slower.
DSC07356.JPG
Here with the plate:
DSC07359.JPG
The plate is not ideal. Thinner would be better of course. But I had it at home.

But it works perfectly:

It's a 1l-bottle with water. The bug is 35mm long, it's the longest one of the set I bought. Here I run it with 12V. I simply switch it on. No potentiometer or something to start it slow. Perhaps for safety unsupervised 9V is better.
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Re: Homemade Yeast Stir Plate

Post by Bushman »

I have all the parts sitting in my outbuilding. I built mine in a cigar box with not a lot of success but this thread has me thinking about getting back to it.
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Re: Homemade Yeast Stir Plate

Post by Pesty »

Thermaltake makes a desktop USB fan.. Image
You can cut out the center of the fan guard, gtlue on the magnets and use any USB wall charger and you have a stir plate with speed control for less than 20 bucks.

Staples sells the fan or you can find it on Amazon and the like.
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Re: Homemade Yeast Stir Plate

Post by rgreen2002 »

You can also find good rare earth magnets in most old computer hard drives. Plenty of youtube vids on how to get them out if you have a few lying around. Der wo is right... the neodymium magnets can get really pricey :mrgreen:
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Re: Homemade Yeast Stir Plate

Post by Danespirit »

Der Wo....are you reading my mind??? :ebiggrin:
It's about the exact construction I made for my magnetic stirrer.
I glued them to the fan with Cyanoacrylate..a little drop beneath each is sufficient to hold them rock steady.
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