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

I quit. I am so tired of dicking with this stirplate build. I've tried four different power supplies, two different fans, three different magnets, and I still can't get it to work reliably. It throws the bar, it stalls (even on high - in a 250ml beaker) and then works fine for the next starter.

I've spent probably $40 in parts (see above), countless hours and it's just not worth it anymore. I ordered a stirstarter from Bell's General Store. For $42 I'll have a reliable stirplate that I don't need to worry about catching on fire because it decided to stall (again!) at 2am.

In my experience, the bar will get thrown if either (1) the magnetic connection is weak, (2) the fan is moving too fast or (3) the flask is not centered (or all three).

I fixed #1 by bringing the fan's magnets closer to the flask by cutting a hole in the stir plate and raising the fan so the only thing between the magnets and the stir bar is the flask bottom.

I fixed #2 by adding a voltage regulator to the circuit so the rheostat has more finely-grained control.

I fixed #3 by noticing the bar rattles the least when centered in the flask. Me not dum.

Now I have 2 stir plates that couldn't be more reliable with as much as 5L starters. In the end, buying a good stir plate is probably smarter, but less fun, IMO.

I've had enough fun.

It does have a nice 1.2L starter of WLP007 grown from a slant on it right now. I'll use it as a backup or in case I want to make two starters for a double batch one day.

Chalk one down for the WIN side! Came out great. I think 12v power supply is a bit much for a 500ml though. May down grade to 9v... or upsuze to 2000ml.

I'm not sure how to do the math for a motor but I think it is better to drive it with the 12 volts it is rated at and control speed with the proper pot. Lower volts may indeed lower speed but it increases current and heat. With 12 volts, I can run mine from full speed all the way down to dead crawl just before stalling. Full speed will throw the bar right quick but I have not had any issues with the motor or pot heating up running it slow either.

I want to say my magnet is about 1 or 2 mm under the housing so I can get a really good vortex going. It has never thrown on me and I'll have 500+ ml in it and the bar will actually be exposed to air. Now my question: I've created the stir plate and have a Erlenmeyer, how long do I run the starter for a 5 gallon batch? 10 gallon batch?

BurgBrewer said:

I want to say my magnet is about 1 or 2 mm under the housing so I can get a really good vortex going. It has never thrown on me and I'll have 500+ ml in it and the bar will actually be exposed to air. Now my question: I've created the stir plate and have a Erlenmeyer, how long do I run the starter for a 5 gallon batch? 10 gallon batch?

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Not sure how long but for a 10 gallon batch, you might want to step it up to make sure you have enough yeast cells.

I usually run my starters two days before I pitch - just to be sure the yeast had a couple days to eat the barley I fed 'em and multiply...

I finally found a suitable case for my stir plate. I had been just bridging my jar over 4 screws that I set into the mounting holes of the fan.

As you can see, it is just a cheap plastic storage container that I found in a drawer. It is a little deeper than I would have preferred bit it works well. As it turns out, it is just big enough to store the brick and cord in the case when not in use.

Using a coffee pot as my flask but what the heck, it was already on hand and it seems to work well.

I think the only thing I actually purchased for this build is the threaded rod for the standoffs. Everything else was found in the junk drawers.

Hey Everyone, I have two questions about this build I was hoping to get your input on:

1. Has anyone used this stir plate on both a 2L and a 5L flask? I seached "5L" using the Search this Thread tool, but nothing came up. I sometimes brew big lagers like Doppelbocks and it would be nice if the stir plate was powerful and reliable enough to stir both the 2L and 5L flasks.

2. I have a 12V .13A 120mm fan. I got the design wired up last night, but I couldn't get a reliable spin, so I'll be tinkering with it more tonight. My question is about the fan's amperage, at .13A, this seems lower than other case fans. Do you see the low amperage as a hinderance to a 2L or 5L capable stir plate?

Pie_Man said:

2. I have a 12V .13A 120mm fan. I got the design wired up last night, but I couldn't get a reliable spin, so I'll be tinkering with it more tonight. My question is about the fan's amperage, at .13A, this seems lower than other case fans. Do you see the low amperage as a hinderance to 2L or 5L starters?

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I don't know that I have a direct answer for your question, but I did have a similar problem with a weak spin. The cell phone charger I used was only rated to 250 mA and the fan would spin pretty slow, even at max speed. I bought a cheap ($3 or so) 1000mA charger on Amazon and now it spins pretty well for my 2L starters. Still too weak for a 5L I'm sure, but it's a step in the right direction. Hope this helps!

Thanks Mojo, I think I have the opposite problem. My fan seems to spin too fast. Even with the pot, I cannot seem to notice a difference in the fan's speed. I don't have a multimeter to test the pot, so I'll just assume it's working for now.

I may end up changing out my 12V power supply for a 9V, but the 9V I have is only rated for 180mA. I'm a noob with this electric stuff, but I thought the amperage of the power supply should be twice the device it's powering (the fan is .13A).

Pie_Man said:

Hey Everyone, I have two questions about this build I was hoping to get your input on:

1. Has anyone used this stir plate on both a 2L and a 5L flask? I seached "5L" using the Search this Thread tool, but nothing came up. I sometimes brew big lagers like Doppelbocks and it would be nice if the stir plate was powerful and reliable enough to stir both the 2L and 5L flasks.

2. I have a 12V .13A 120mm fan. I got the design wired up last night, but I couldn't get a reliable spin, so I'll be tinkering with it more tonight. My question is about the fan's amperage, at .13A, this seems lower than other case fans. Do you see the low amperage as a hinderance to a 2L or 5L capable stir plate?

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Bump

Just wanted to say thanks for this tutorial. I now have my own stir plate, thanks to you. Lots of fun to build, with such clear and easy directions!

I've got a 9v 1000mA power supply and mine works great for 2L starter, even on lowest speed. I'm guessing it'd work for 5L, you don't really need a full vortex.

Cool. I just got mine working with a 9v 180mA power supply. The power supply is not double the amperage of the fan (130mA), but it seems to be working. I read somewhere the ps should be double whatever it's powering. No vortex with the 2L starter, but still keeping things in suspension. I do have a 12v power supply, but that was throwing the bar. I may give it another try after I reorient the magnets.

Thanks to the OP for the build. Getting good magnets and the polarity correct was the toughest part for me. I tried using magnets salvaged from an old hard drive at first, but they didn't seem strong enough, so I bought magnets from Ace hardware.

I have a few spare magnets. If anyone needs a pair of them, PM me. No charge

Love it!

It took about 3 hours total, not including the Radio Shack and Lowe's runs, but it works great! The hardest part was actually getting the position of the fan and magnet just right so that the stir magnet wouldn't fly off to the side of the flask. With a little patience and tweaking though, I was able to fine tune it so that I could crank the rheostat all the way up and get a good vortex of water with no "pop-offs".

Thanks so much for the instructions! This is way better than spending $100 on a stir plate.

As an aside, Radio Shack has raised their prices a bit. This cost me about $25 total.

Made mine about a month ago using the instructions and advice from folks in this thread. I'm an electrical dummy but still managed to make it work after only killing one PC fan wiring it up backwards .

The second fan I found was a tight fit in the project box but it works well. I can only run it about 1/2 speed though as it gets spinning too fast and will throw a 1" stir bar. I've mad e a few starters with it so far, it's worked out well.

Just finished my stir plate today. Used 1/4" square magnets and a fan from amazon. I thought I had a problem with the fan being too big at first but I turned a problem into a solution. Instead of using bolts to secure the fan, It had a nice snug fit already and I just put some hot glue on the sides for insurance. Works great! Power supply is a 9.6V 50mA charger from an old RC transmitter. Thought it might be too small but it puts a nice dimple in the water on high which I think is good enough.

Here's mine. Just made it last night following these directions. Went in to RadioShack with a parts list and they found everything I needed within a minute. Put one of my left over beer labels on it. Mine is running off of a 12v 200mA

Would it spin faster with a 5v that's 2.8A?

Those are a couple of nice builds. Why would anyone pay the big bucks when you can make one of these so easily and cheaply?
Mine isn't as nice looking but then I made mine from junk I had laying around. I think the only thing I bought was the stir bar.

omfgzorz - no, it would spin slower on 5V.

omfgzorz said:

...

Mine is running off of a 12v 200mA

Would it spin faster with a 5v that's 2.8A?

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Nope. It would spin slower.

The voltage causes the current to flow, and the amps rating is a maximum current the power supply will deliver on a constant basis while staying reliable. If you connect something to that power supply that allows 500mA to flow when it's given 12v, the power supply might do one of several things. It might give 12v for a moment but then slide down to 10v or 7v as its capacitors empty and it can't fill them back up fast enough. Or it might deliver 12v and 500mA, but heat up and fail after a few weeks. Or, it might turn out that the manufacturers simply labeled it to match the device it came with, and it might supply 500mA just fine.

If you take a fan that normally draws 1A at 12v, and connect it to a 5v power supply, it will draw only a fraction of that 1A and spin slowly. OTOH, if you connect that same fan to a 12v power supply rated for 0.2A, it will overdraw the power supply and spin slowly.

Fortunately, no respectable computer fan needs more than 200mA! So you're good. Keep it on the 12v. (Unless it spins too fast, then 5v is an option to slow it down!)

(Edit) Second guessed myself, and went to verify... Turns out there are a few specialty fans that draw more than 200mA. Usually they're in the very high-rpm high-airflow category, mainly made for servers. Spot checking fans that the average consumer would buy I saw specs mainly under 100mA.

You can check with a voltmeter. If the power terminals drop below 11v when you plug in the fan, you may be overloading the power supply. (You probably aren't though, I wouldn't worry.)

I'm having a problem where mine just twists back and forth and never actually spins all the way around.

Is this because my fan is turning too fast or not fast enough? If it's too fast then the old plugin rheostat I have isn't going to work for me.

Beernik said:

I'm having a problem where mine just twists back and forth and never actually spins all the way around.

Is this because my fan is turning too fast? If so, then the old plugin rheostat I have isn't going to work for me.

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Did you start off slow to get the bar going first then slowly turning it up as it gains speed?

The bad news is I don't think there is much difference between the slow and the fast setting on my rheostat.

The good news is I figured out I had some magnetic interference from a piece of metal. I removed it, positioned the magnet better and it works.

It also looks like my next upgrade is a 3L or 4L flask because my 1 gallon jug doesn't have a flat interior bottom.

I don't need to pull a huge whirlpool for a starter, do I? I'd think that would be bad.

All you're trying to do is turn the wort over occasionally to expose it to the oxygen at the surface. You're not trying to macerate the yeast From the picture, what you have there is fine...

Cheers!

Cool, then I don't think I even need the rheostat. That's its top speed. Turning the rheostat down looks pretty much the same.

Thanks.

For those that want to be creative with it; Go to a thrift store and find you a cool box to use instead of a plastic poo box. I used a wood bible box for a bit until I found my sweet german (I think) kids mini toy box. Don't limit yourself to plastic boxes. Have fun with these projects. This is mine throwin 5L back.

Greatest stir plate enclosure ever...I'm looking every time I hit a thrift store!

TANSTAAFB said:

Greatest stir plate enclosure ever...I'm looking every time I hit a thrift store!

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That's what I am talking about!

TANSTAAFB said:

Greatest stir plate enclosure ever...I'm looking every time I hit a thrift store!

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do you have to blow on it to make it work?

iluvmysh said:

do you have to blow on it to make it work?

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That's fu@#in funny!

Mellow52 said:

This is a fool proof wiring diagram. All parts is obtainable from your local Radio Shack.

This will allow for perfect speed control. Using just a potentiometer will work at first but wont last and last. You wont get good speed control and using lower volt DC adapters for speed control is silly. Don't do it, build it right.

Also checkout this handy link: http://www.stirstarters.com/instructions.html

If you like DIY then build one if not just order one from here, it is much easier and only marginally more expensive than parting and building it yourself.

Cheers to happy yeasty beasties!

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Hi Guys,
I have built 2 stir plates using this schematic. The first stir plate worked perfect. I couldn't be happier. The second stir plate works but the potentiometer basically is off when turned down and if you turn it a little bit the fan goes from off to full speed.

I read and re-read this schematic, checked it against my wiring and everything looks right. I swapped pots, switches, and power supplies (one used a 12v and the other a 5v) but none of those were the problem. It's somewhere in the circuit but seemingly not the wiring. I am thinking it might be a bad resistor but I am totally out of ideas. Can anyone think of what component or area of the circuit might be the problem to cause a pot to have no adjustability in this circuit?
Thanks in advance.
Hovik

Great thread.

I bet somewhere along the way a major stir plate manufacturer happened upon this thread, did a "D'oh !" and forehead slap and said "so this is where our stire plate sales have been going" !

Beernik said:

It also looks like my next upgrade is a 3L or 4L flask because my 1 gallon jug doesn't have a flat interior bottom.

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I only use 1 gallon jugs that don't have flat bottoms and they work fine for my stirplate starters.

brewman ! said:

Great thread.

I bet somewhere along the way a major stir plate manufacturer happened upon this thread, did a "D'oh !" and forehead slap and said "so this is where our stire plate sales have been going" !

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If you think about it, we're not really building these for less money. We're just not assigning a dollar figure to the time we spend assembling. If someone asked to pay you to spend all day building these, the dollar figure would go up a bit!

misterbk said:

If you think about it, we're not really building these for less money. We're just not assigning a dollar figure to the time we spend assembling. If someone asked to pay you to spend all day building these, the dollar figure would go up a bit!

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When it is a hobby and you are doing it for fun, you can't count your time as cost. That's part of the hobby. How many hobbies do you know where there can actually be a cost savings?
Between the DIY projects for equipment and the fact that the end product is cheaper than I can buy it in the store, this is the greatest hobbie on earth!

Hovik said:

Hi Guys,
I have built 2 stir plates using this schematic. The first stir plate worked perfect. I couldn't be happier. The second stir plate works but the potentiometer basically is off when turned down and if you turn it a little bit the fan goes from off to full speed.

I read and re-read this schematic, checked it against my wiring and everything looks right. I swapped pots, switches, and power supplies (one used a 12v and the other a 5v) but none of those were the problem. It's somewhere in the circuit but seemingly not the wiring. I am thinking it might be a bad resistor but I am totally out of ideas. Can anyone think of what component or area of the circuit might be the problem to cause a pot to have no adjustability in this circuit?
Thanks in advance.
Hovik

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Since you say you swapped the pot, then the only thing left is the voltage regulator. Have you tested the output with a meter?
My first thought would have been the pot. Either it is bad and going from off straight to full on, or the value is not what you think it is. If the pot is bigger than you think, that is exactuly what it would do.
If the pot checks out, put the volt meter on the output (without the fan) and watch the voltage change as you turn the pot.
Another thing to check is that the terminals are correct on the 317 regulator. If the input and output are swapped, that might cause the problem too.

According to Mellow52, a pot alone wont last and last. I'm not sure why, I've never heard that before. I'm not an engineer so if there is a reason that current control is not as good as voltage control, I would like to understand. Functionally, they both see to be the same.

Most DIY's if heard of have been with a pot alone. In my case, I used a transistor and pot combination because I couldn't find the right sized pot locally. Same effect as a pot alone but mine seems to be holding up just fine.

Good Luck, let us know what you find

Starrider said:

Since you say you swapped the pot, then the only thing left is the voltage regulator. Have you tested the output with a meter?
My first thought would have been the pot. Either it is bad and going from off straight to full on, or the value is not what you think it is. If the pot is bigger than you think, that is exactuly what it would do.
If the pot checks out, put the volt meter on the output (without the fan) and watch the voltage change as you turn the pot.
Another thing to check is that the terminals are correct on the 317 regulator. If the input and output are swapped, that might cause the problem too.

According to Mellow52, a pot alone wont last and last. I'm not sure why, I've never heard that before. I'm not an engineer so if there is a reason that current control is not as good as voltage control, I would like to understand. Functionally, they both see to be the same.

Most DIY's if heard of have been with a pot alone. In my case, I used a transistor and pot combination because I couldn't find the right sized pot locally. Same effect as a pot alone but mine seems to be holding up just fine.

Good Luck, let us know what you find

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Pot goes from 1.2 ohms - 4.95k ohms. This is very close to the performance of the pot in my working stir plate. Wall wort output is 5.10v. Input side of regulator shows 5.10v
Output shows 1.254vdc when pot closed, only 3.51vdc when is pot open but this is with the fan connected. If I need to desolder it to get a reading I can... let me know. Does this suggest any possible causes?
I checked and the volt regulator seems to be wired correct.

Hey guys, I tore into a old hard drive this morning expecting to find some half moon magnets. All this one has looks to be a round one.

Any particular brand of hard drives that I need to look for?