Diy Computer-fan Stir-plate Build

[pyrosx]

I was looking into all this tonight and sussed out from my elecy mate if i could use a charger (5v) with the fan that needs 12 v he said that it will try drawing the whole 12v out of the transformer and prob cause the fan to burn out quicker (im pretty sure that is what he ment) If u already have the 12V power supply you may as well use it may save your fan in the long run.

Using a bigger power supply and a resistor is going to.... ugh - my elec eng skills have massive cobwebs... higher voltage, so lower current. What this means in practical terms to the fan is beyond me though... probably more current through the coils, so a possibility of more heat and burnout - doesn't feel hot though. I'll keep an eye on it though - I hadn't thought of my ghetto cardboard solution in terms of fuel for a fire :/

Obviously under-powering anything isn't exactly "ideal", and the warranty is probably void - but it cost less than $3 - so i'm comfortable with that.

Once this starter is done i'll probably look at finding a beefier phone charger and include the pot for speed control - probably nicer anyway.

 

[vortex]

I've picked up the parts to build a new dual stir plate, two 120mm fans and two fan speed controllers; hopefully one of these will be powerful enough for a 5L lager starter.

Just wondering though, has anyone cracked open a professional stir plate to see how the magnets are placed/arranged? Just curious, as i've had a few issues with throwing stir bars on my DIY plate and i'm wondering if it's because of the placement of the magnets. I've also had a few thoughts on magnet arrangement, and just wondering how the magnets in a professional stir plate are arranged.

 

[Wimmig]

I just ordered the parts for a stir plate, 12v version. So far, the bits cost $12.50. Going to use a cigar box from work so that's free. All that's left is a stir bar and a flask

 

[black_labb]

I have most of what I need for a stirplate from uni projects. a variable dc power supply (up to 12v), some neodynum magnets and a few small motors that work off 12v. Just need to mount it all together.

 

[Camo1234]

I have just built my first stir plate and having a few issues with getting the stir bar to stop spinning off.


I have a small and large stir bar and have used 2 sets of 8mm x 1mm magnets 3 high so that you have 4 sets across the fan. I can get the small stir bar to spin while I keep the fan going slow but when I speed it up it shots the stir bar off.... the larger stir bar pretty much shoots off straight away...



What do you think my issue is? Are my magnets not strong enough or are they not aligned correctly? with the small one I can get a small vortex but it makes plenty of noise and doesn't really spin quietly... i have the staight stir bars like have been recommended on here, are thesse supposed to go quietly?


Cheers guys, any help appreciated.



Camo

 

[benno1973]

Are you using a flat bottomed flask or something with a flat bottom for the starter? Anything with a slightly domed bottom (V8 jars, glass jars, 2L demijohns etc) are a bitch to get going. Also, if you can get a really slow spin on the stir bar, then you'll be more likely to keep it from spinning off.

 

[Camo1234]

Are you using a flat bottomed flask or something with a flat bottom for the starter? Anything with a slightly domed bottom (V8 jars, glass jars, 2L demijohns etc) are a bitch to get going. Also, if you can get a really slow spin on the stir bar, then you'll be more likely to keep it from spinning off.

Hey mate, i am using a 2 ltr erlenmeyer flask so I assume it has a flat bottom. How vigorous does the whirlpool need to be? is a slow spin ok or does it need to go crazy like the You tube videos? I have the dimmer knob hooked up and can get the small bar slowly spinning well so I might just stick with that for now.

 

[Wolfy]

I have a small and large stir bar and have used 2 sets of 8mm x 1mm magnets 3 high so that you have 4 sets across the fan. I can get the small stir bar to spin while I keep the fan going slow but when I speed it up it shots the stir bar off.... the larger stir bar pretty much shoots off straight away...

What do you think my issue is? Are my magnets not strong enough or are they not aligned correctly? with the small one I can get a small vortex but it makes plenty of noise and doesn't really spin quietly... i have the staight stir bars like have been recommended on here, are thesse supposed to go quietly?

The not spinning quietly would also indicate that it's not-so-stable.
If you've put the magnets the 'right' distance apart (as suggested at the start of the thread) then I'd try adjusting the distance between the flask-bottom and the magnets, either raise or lower it and you should get to a 'sweet spot' where both stir-bars are stable at all speeds. How you raise/lower the distance depends on what enclosure you are using.

The straight stir-bars should be mostly quiet - just a small tinkle-sound as it spins around.

How vigorous does the whirlpool need to be? is a slow spin ok or does it need to go crazy like the You tube videos?

You only need enough of a vortex to mix in oxygen and to stir the yeast - so it does not need to be a super-whirlpool like many videos.

 

[Camo1234]

The not spinning quietly would also indicate that it's not-so-stable.
If you've put the magnets the 'right' distance apart (as suggested at the start of the thread) then I'd try adjusting the distance between the flask-bottom and the magnets, either raise or lower it and you should get to a 'sweet spot' where both stir-bars are stable at all speeds. How you raise/lower the distance depends on what enclosure you are using.

The straight stir-bars should be mostly quiet - just a small tinkle-sound as it spins around.

You only need enough of a vortex to mix in oxygen and to stir the yeast - so it does not need to be a super-whirlpool like many videos.

Cheers... I have it going now, well enough to grow yeast anyway!

It is literally a computer fan with a few cardboard spacers and a tupperwear lid at the moment with the flask on top.... it is spinning nicely with a little noise.

I'm not the most handy person going around but slowly getting these things going... Haven't really been a "build it" person until I started brewing.... I would usually just buy things i needed... But I am starting to actually enjoy the feeling of pride when I put it together.... So far I have done my STC1000 (was nervous I would kill myself so got a sparkie to look over it and he was happy :icon_cheers: ), computer fan blower to cool my keggerator font and now my sort of stir plate!


Time to think about an enclosure!



Camo

 

[Wolfy]

It is literally a computer fan with a few cardboard spacers and a tupperwear lid at the moment with the flask on top.... it is spinning nicely with a little noise.

Easy then - add/remove spacers until it all spins fine.

 

[Camo1234]

Hi Guys


Sorry, school boy question here.... First go at a starter and also using a stir plate and not really sure if I am seeing a krausen or just bubbles from the airation.






This is the second step, first step was 1 ltr with half a smack pack, the stir bar fell off so the yeast settled after 24 hours so I stepped it up with 1.5 ltrs and now after 48 hours this krausen is still there.


I feel like my first few brews watching it like a hawk!


ps... yes that is my dodgey stir plate! enclosure will come another day.

also, i am heading camping for the weekend so will the starter be OK if I just put it in the fridge from Thurs night to Sun night and then pitch Sun night?



Cheers Fellas... Camo

 

[Camo1234]

Bump???

Hi Guys


Sorry, school boy question here.... First go at a starter and also using a stir plate and not really sure if I am seeing a krausen or just bubbles from the airation.

View attachment 53065

View attachment 53066


This is the second step, first step was 1 ltr with half a smack pack, the stir bar fell off so the yeast settled after 24 hours so I stepped it up with 1.5 ltrs and now after 48 hours this krausen is still there.


I feel like my first few brews watching it like a hawk!


ps... yes that is my dodgey stir plate! enclosure will come another day.

also, i am heading camping for the weekend so will the starter be OK if I just put it in the fridge from Thurs night to Sun night and then pitch Sun night?



Cheers Fellas... Camo

 

[Wolfy]

Sorry, school boy question here.... First go at a starter and also using a stir plate and not really sure if I am seeing a krausen or just bubbles from the airation.
...
also, i am heading camping for the weekend so will the starter be OK if I just put it in the fridge from Thurs night to Sun night and then pitch Sun night?

Why does it matter? What are you actually trying to ask? You're looking to grow yeast not ferment starter-beer.
If your yeast starts fermenting (when you see krausen/activity), it's already grown as much as it's going to - usually that takes 12-24h (48h maximum) after that time having the stir-plate turned on is not essential.

If you are asking has it done it's thing, grown, fermented, behaved as expected:

• Turn off the stir-plate, and view the yeast-sediment that settles to the bottom - you should have a nice layer of yeast (much more than you started with).
• Check the gravity, if the gravity has dropped (it likely grew, fermented and finished all while you were watching) then things are done.

The brown-yeast-skum-layer on the side of the flask that is higher than the froth, indicates to me that it's done and dusted, fermented and finished - but that's a guess that does not need to be made if you do the two things above.

Putting the yeast in the fridge for a few days should not hurt things too much.

 

[Camo1234]

Hey Wolfy, cheers for the reply. You have explained it perfectly! I was waiting for the krausen to settle out as I thought i had read somewhere that I should let the starter ferment out :blink:

 

[Wolfy]

I was waiting for the krausen to settle out as I thought i had read somewhere that I should let the starter ferment out :blink:

If you are stepping a starter (as you did) there is no need to wait for it to ferment, simply step it up after about 12-48h (depending on size, yeast etc).

On the last step of the starter (especially if the yeast will be stored for a few days) it can be beneficial to let it ferment-out and then give the time for the yeast to settle - however this process (again depending on size, yeast etc) is still usually very fast 24-48h.

 

[crd0902]

Hey all I'm just gettin started building my stir plate. I have a fan and a 5 and 9 volt power supply. Trying to find adimmer. What size magnets are good. I have a choice 10 by 1 mm, 8 by 1 mm and some three mm and five mm thick. Not sure what to go for. Also I cant find a stir bar without the pivot ring. Any advice cheers

 

[Gar]

Dimmer - the guts can be taken out of the box if you'd like to make it more compact.
http://www.ebay.com.au/itm/New-12V-8A-Led-...=item256cd4bb47

5mm thick magnets sound nice... old HDD magnets are good too.

Got my stir bar without pivot ring from http://www.livingstone.com.au they're a bit finicky with who they deal with though, not sure why they trust me :lol:

 

[crd0902]

Thanks I found some stir bars on ssapl.com so I'll try your site if I have no luck. I think I'll go for the 5 mm magnets as I just read somewhere else they are good ones. Thanks for the advice. I'll be back once it's built

 

[bullsneck]

I'm having trouble keeping the stir bar on. I have exactly the same system as you Wolfy. I bought what you did so it would work.

However, the stir bar keeps flying off, even at the lowest speed. My thoughts are because it is a bit longer than yours, measuring 5cms or so. Will a smaller stir bar work?

 

[Wolfy]

I'm having trouble keeping the stir bar on. I have exactly the same system as you Wolfy. I bought what you did so it would work.

However, the stir bar keeps flying off, even at the lowest speed. My thoughts are because it is a bit longer than yours, measuring 5cms or so. Will a smaller stir bar work?

Could be because the stir-bar is longer, especially if your magnets are close together, or could be that the height between the bottom of the flask and the magnets is a problem, so try adjusting that first.