Building My Own Yeast Stirplate Device

[pdilley]

Well I decided to start the mad scientist Yeast Stirplate project.

I have already removed rare earth magnets from two discarded computer hard drives. Of note, the Quantum brand had very large very powerful magnets, the Western Digital had smaller less powerful magnets but still enough to pinch your finger if you got it stuck between two of them!

I went down to Jaycar and picked up some parts, LM317T voltage regulator, a .1uF ceramic disc capactitor, a 1uF polarised capacitor, 10K Ohm Linear potentiometer, 1K Ohm resistor, a knob for the potentiometer, a small circuit board with holes in it to mount all the components and solder wire on the other side.

I also got an old computer power supply from a workmate since I only run Macs and they just have not died on me like my old PCs used to do. I stripped out the 12V DC fan, and unsoldered the fan connector on the power supply circuit board. I also removed a very large aluminum heat sync to use with the LM317T.

I went down to Bunnings and got a craft box from the craft section. I will coat it with water proof covering, probably spray on or brush on if I find it costs to much for spray cans. I will cut a circle hold in the lid so the magnet can spin right next to the bottom of the glass without directly touching it. I am also contemplating gluing a thin veneer of lexan material to the top to completely waterproof the unit so no liquid leaks down the circle cutout in the top.

Rubber feet on the bottom to raise it off the counter in case of liquid spills. Optional rubber layer on the top to help grip the glass flasks or jars in case of bumping the unit -- hopefully prevent some nasty falls

I ordered a 12Volt AC/DC wall wart power supply 1Amp from China. $4.40 for the Australian version including free shipping to Australia from Hong Kong. Or I could have been dumb and went to Dick Smiths and paid $29 for the same bloody thing.


Pictures so far:

Excuse the crap quality, I only had my phone with me in the work shed and my Dad stayed for 5 weeks and turned my shed upside down only to leave just a short while ago. Cleanup is planned but not looked forward to

First off the circuit to build the speed controller for the fan:


Starting work on the circuit board, epoxied the heat sync in place, LM317T mounted. Wire leads soldered to all three pins on the bottom. Epoxying the 12VDC fan connector (what you see being clamped) that I had previously de-soldered from the computer power supply. Mounted the 1K Ohm resistor and thats all I had time for before coming back inside.

I will only use less than 1/4 of that component holding board material. I will saw off the 3/4 and put it back in reserve for the next mad project.

Next up is the craft box from Bunnings. Using a 1/4 inch forstner drill bit I put a lovely hole in the center of the panel to mount the 10K Ohm Linear Potentiomenter that will be the adjustment knob to control the speed of the 12VDC fan.



I then got the potentiometer jigged up and read to solder on some wire leads. But then I got tired and decided to pack it in for the night.




Before leaving I wanted to get a picture of what the control knob will look like. I went to town and spent more on the knob because it has 10 position markings and lots of little markings in between. This should let me put an alignment line on the face of the box and then dial in exact speeds depending on the viscosity of the wort or must that will be having its yeast stirred like buggary.




Once completed it will work like the unit shown in this YouTube video:




Why do we use a Stirplate?


You get a boat load of yeast to pitch compared to any other method out there!

Just look at this!

Yeast Farming here I come!!


P.S. Careful, even a 2 litre flask might not be enough! 18 hours into making the above yeast!



Cheers,
Brewer Pete

 

[raven19]

Looks great thus far Pete. Wish I understood all this electronic engineering!

 

[LethalCorpse]

Well, that's quite a write-up there Pete, and fairly neat work. I have some questions though:

Why do you have such a monstrous heatsink?
Why have you used MDF, along with all the extra stuff you've had to think about for waterproofing, when a plastic jiffy box would have been cheaper and solved all those problems?
Why are you using unclad punched resin when veroboard is just as cheap, and actually connects stuff for you?
What's the second thermal pad and mounting screw on the heatsink for?
Why are you soldering the pot with wires in free air when it could (and should) just as easily be mounted on the board?
Did this really need its own thread, when there's already an extensive thread dedicated to this very project?

 

[pdilley]

Well, that's quite a write-up there Pete, and fairly neat work. I have some questions though:

Why do you have such a monstrous heatsink?
Why have you used MDF, along with all the extra stuff you've had to think about for waterproofing, when a plastic jiffy box would have been cheaper and solved all those problems?
Why are you using unclad punched resin when veroboard is just as cheap, and actually connects stuff for you?
What's the second thermal pad and mounting screw on the heatsink for?
Why are you soldering the pot with wires in free air when it could (and should) just as easily be mounted on the board?
Did this really need its own thread, when there's already an extensive thread dedicated to this very project?

Monstrous because I am recycling. That came out of the computer power supply for free.
MDF because it's cheaper than plastic cases at Jacar by 1/3rd. I have finishes in my shed so no extra cost. I have lexan so no extra cost. The box is very thick compared to most plastic boxes I looked at and would support more weight without flexing the lid.
Unclad resin because that's all that was at Jaycar near me and I weighed day of driving, petrol and frustration trying to fnd better. In the past I etched my own circuit boards but not going to the expense for this project.
Second screw is because of recycled heat sync.
If I had my dithers I'd try and get everything for free off the old circuits but no LM317.

To do this my preferred way would be an AC fan and fan controller by they are 80 +36 over here when I'm used to paying 7 dollars in the states. I'm just not that mch of a sucker to pay those prices. I was thnking of using a cieling fan as that gets you AC but I'd have to custom build a platform for the spindle. I'd still be facin the obscene pricing of fan controllers in Australia so im going with the DC solution for now.

 

[LethalCorpse]

Fair enough. And the last question?

 

[pdilley]

Fair enough. And the last question?

There are 20 stir plate posts. I didn't think it was centralised from that so I posted in my own.

 

[pdilley]

Looks great thus far Pete. Wish I understood all this electronic engineering!

Its just building the equivalent of the faucet on your garden hose. Controls the flow from a trickle to full bore on. So the fan goes very slow to top speed. Thats all it is. Rather simple. That picture includes shapes that represent items you buy at an electronics component shop like Jaycar, you might do better just seeing photographs of the components all wired together instead.

You can buy PC fan speed controllers already build for you from ebay for about $5-12 so you might want to go with that instead. You have to check the specs to see if they take 12V which is what you want. If they don't specify then you can usually assume 12V as thats what most of the PC cooling fans are rated at. But standard disclaimers apply aka do your homework.


I think I hit the jackpot, found a source for AC 240Volt 50/60Hz Ball bearing 120mm cooling fans for $9 AUD which beats buying from any storefront in Australia. I may skip the DC route entirely if I go with this. I've always preferred AC over DC, easier to build only two components to wire up and no building custom circuits and DC fans don't do so hot under any sort of load.

I also spotted bathroom fans from Bunnings for $15. If its non inductive can use a standard dimmer to control it. With this, however you need to build something to hold the magnet to the spindle as the standard plastic fan blade has airplane style pointed/rounded nose cone shape, not flat.

I also scanned the Jaycar website last night, the salesman started talking to me when I was only 1/2 way through scanning all the kits on the wall so I missed the kit you can buy with an LM317T already in it. Part no. KA1797. It uses jumpers to set the voltage so you just bypass them and wire up your potentiometer and you are set to dial in any speed you want. No need to buy a circuit board or any stuffing around with proto boards!


If I go AC I'll switch an an industrial style design using a single sheet of thick lexan and underneath have an enclosed circuit box holding all the wiring out of the way something along the lines of a small stir table skipping the box concept entirely. Worst case I can order a Solid State Variable Speed AC Motor Control for 240volt from the United States for $15 USD and have it shipped over here.


Cheers,
Brewer Pete

 

[hazard]

I think I hit the jackpot, found a source for AC 240Volt 50/60Hz Ball bearing 120mm cooling fans for $9 AUD which beats buying from any storefront in Australia. I may skip the DC route entirely if I go with this. I've always preferred AC over DC, easier to build only two components to wire up and no building custom circuits and DC fans don't do so hot under any sort of load.

IIf I go AC I'll switch an an industrial style design using a single sheet of thick lexan and underneath have an enclosed circuit box holding all the wiring out of the way something along the lines of a small stir table skipping the box concept entirely. Worst case I can order a Solid State Variable Speed AC Motor Control for 240volt from the United States for $15 USD and have it shipped over here.

Cheers,
Brewer Pete

Yes, but how do you control the speed on an AC motor? Speed is dependent on mains frequency which is 50 Hz. Speed does not vary with more voltage (just more torque I think). In any case the LM317 only works with DC, it will not regulate AC. A variac can change AC voltage, but does nothing for the frequency ie doesn't control speed.

hazard

 

[~MikE]

i just yesterday finished mine. i just have a set of resistors to control the speed, but i think my motor at top speed is overkill (12V motor from jaycar). it has 2 lots of 2 rare earth magnets on it, the bottom ones glued and the top ones just sitting there magnetised in place (bear in mind these are a bitch to pull apart) - at top speed, not shit, it sends the top magnets flying across the room. i might get a 6-9V power pack for it...
here it is at a workable speed.

 

[pdilley]

Yes, but how do you control the speed on an AC motor? Speed is dependent on mains frequency which is 50 Hz. Speed does not vary with more voltage (just more torque I think). In any case the LM317 only works with DC, it will not regulate AC. A variac can change AC voltage, but does nothing for the frequency ie doesn't control speed.

hazard

The Solid State controller (I don't know if anyone in Australia has heard of these things, I can't find anything when limiting search to Australia only) is an already built and fully complete control unit that provides infinite variable speed for shaded pole and PSC motors. These are normally used to control ceiling fans at full variable speed. Solid State controllers will handle Shaded Pole, Permanent Split Capacitor and AC/DC Electric Motors.

The LM317T is for (old school) DC motor applications, if I go AC I will save the LM317T and built a variable power supply by picking up a bridge rectifier and some more misc components and use the box to power future electronic hobby projects and instead get an AC 240Volt Fan and use the Solid State unit from the States. Two components, wire them together, wire in a power lead and done!

Cheers,
Brewer Pete

 

[pdilley]

i just yesterday finished mine. i just have a set of resistors to control the speed, but i think my motor at top speed is overkill (12V motor from jaycar). it has 2 lots of 2 rare earth magnets on it, the bottom ones glued and the top ones just sitting there magnetised in place (bear in mind these are a bitch to pull apart) - at top speed, not shit, it sends the top magnets flying across the room. i might get a 6-9V power pack for it...
here it is at a workable speed.

Looking good there. Making me jealous

I know what you mean by pulling the magnets apart.

If you have the room a good magnet setup with 4 magnets is --++ creates a nice polar spread.

Because of the curved jellybean nature of the recycled magnets taken from computer hard drives some speculate that the centre of balance and the centre of magnetism might not line up and cause stir bar stability issues. Of course check for flat bottom in your flask or jar first. I've seen plenty of people using standard quart canning jars instead of getting flasks as an option. So long as the bottom is flat, almost anything will do.

Now you don't want the magnets right on the fans if they pull the fan down against the motor and make spinning difficult -- You'll end up burning out your fan motor! Same if you leave the unit on mistakenly and not enough energy to start the blades spinning, a stuck fan will burn out as easily as one way overloaded. Another reason why I prefer AC fans to DC. I'm considering a nice thick disc of high density foam cut out and glued on top of the fan with the magnet/s glued on top of that. Gets them out of proximity to the fan itself so the magnetic field has less of an effect.

Now make some yeast!


P.S. Your vortex looks nice but with yeast don't make a very powerful vortex as you don't need that to get your yeast going, just enough to get it staying in suspension is all you want to dial in.

Cheers,
Brewer Pete

 

[mika]

If you look under 'Tightarse stirplate' thread (or some such) Lethal Corpse has a bit to say on the AC motor controller dealio.

 

[pdilley]

If you look under 'Tightarse stirplate' thread (or some such) Lethal Corpse has a bit to say on the AC motor controller dealio.

Thats a great thread name!

I looked at the circuit designs including the 555 timer circuit but its not DC motor control I'm after in my latest posts, its AC motor control. I'm pretty much set as is for the DC side. PWM control of a DC Motor is piss easy. PWM control of an AC motor is challenging, as both frequency and voltage must change together. And if using MOSFETs for AC will need to be in a push pull arrangement or H-bridge. Again I'd get the solid state AC motor controller already built for $15 USD and have it shipped to Australia if going with an AC fan solution its just not worth trying to design your own controller and build it at that price. And beats the rip off price Bunnings charges for a cheezy simple 3 way fan controller switch by a country mile. Its rated over 2.5 AMPS so its got a wide safety margin for a simple fan. On/Off + Linear adjustment all in one.

I also got a simple brain storm idea for any issues from that post, cheers for that! A simple plastic rubbermaid tub on top of the stir plate and the flask or jar placed inside that and you have a huge volume capacity moisture barrier between the stir plate and your glass jar to hold any foam blow overs.

I saw a link to a German language instruction page that is almost the idea of the lexan stir table idea I was thinking of, but its still DC and its got the P/S / Controller separate from the table and is very small, I was thinking something the size of the laptop, with the wall mount solid state controller mounted far to one side near the edge. Combined with a big plastic rubbermaid style container from the $2 shop I think I'd be set.

Cheers,
Brewer Pete

 

[LethalCorpse]

PWM control of an AC motor is challenging, as both frequency and voltage must change together.

That's basically the crux of my comments on AC motor control from thath thread that mika was referring to. AC motors are a pain in the bum to control, particularly when you don't know what sort of motor you're dealing with. DC fans are easy - as you've discovered, an LM317 or PWM circuit takes care of it, and the fans are cheap.

Incidentally, that thread was at the root of my earlier comments. Sorry if you hadn't seen it before, but perhaps I might quietly suggest you try a search next time?

 

[pdilley]

No worries,

Feel free to suggest anything you like.

 

[Fourstar]

i just yesterday finished mine. i just have a set of resistors to control the speed, but i think my motor at top speed is overkill (12V motor from jaycar). it has 2 lots of 2 rare earth magnets on it, the bottom ones glued and the top ones just sitting there magnetised in place (bear in mind these are a bitch to pull apart) - at top speed, not shit, it sends the top magnets flying across the room. i might get a 6-9V power pack for it...

Mines becoming a PITA. Im waiting to get my new rare earth magnets from dealextreme. my current ones are from a dead HDD, i tried 2 magnets stacked and the stirbar would fly off rather easily ive even gone to the trouble of breaking them, offset with different polarisations and still the stirbar flies off. i get the slightest dimple in my flask and its operational. but just to get it to that point it usually takes around 5-6 goes. Hopefully stronger magnets are the answer and help hold the stirbar centered.

 

[WitWonder]

Merge!

http://www.aussiehomebrewer.com/forum/inde...91&hl=tight

 

[sumo]

My toolbox stir plate... great little thing as the toolbox cost less than a jiffy box!

 

[SJW]

Well, that's quite a write-up there Pete, and fairly neat work. I have some questions though:

Why do you have such a monstrous heatsink?
Why have you used MDF, along with all the extra stuff you've had to think about for waterproofing, when a plastic jiffy box would have been cheaper and solved all those problems?
Why are you using unclad punched resin when veroboard is just as cheap, and actually connects stuff for you?
What's the second thermal pad and mounting screw on the heatsink for?
Why are you soldering the pot with wires in free air when it could (and should) just as easily be mounted on the board?
Did this really need its own thread, when there's already an extensive thread dedicated to this very project?

I think what LC is trying to say is, well done mate, good job.
All it needs to do is ..........well..........STIR.

 

[~MikE]

Looking good there. Making me jealous
P.S. Your vortex looks nice but with yeast don't make a very powerful vortex as you don't need that to get your yeast going, just enough to get it staying in suspension is all you want to dial in.

Cheers,
Brewer Pete

i grow yeast at uni with a stirrer like this, just didn't have the setup at home. i might vortext the crap out of it at the beginning to aerate the media, but otherwise yes, low speed.

Mines becoming a PITA. Im waiting to get my new rare earth magnets from dealextreme. my current ones are from a dead HDD, i tried 2 magnets stacked and the stirbar would fly off rather easily ive even gone to the trouble of breaking them, offset with different polarisations and still the stirbar flies off. i get the slightest dimple in my flask and its operational. but just to get it to that point it usually takes around 5-6 goes. Hopefully stronger magnets are the answer and help hold the stirbar centered.

yes, i got 4 rare earth magnets, quite powerful ones and was, if anything, regretful of not getting the extremely powerful ones. also, try and distance the magnets to suit your stirbar.
Mike