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Old 05-09-2006, 01:18 PM   #21
Baron von BeeGee
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Quote:
Originally Posted by DyerNeedOfBeer
I use oxygen to aerate my starters and they come out very nice. Do these stir plates really make that much of a difference?
They apparently make quite a large difference. There's an article on the Maltose Falcons website with good details, but I don't have a handly link to it. I believe a big factor is that the stir plate keeps the yeast in suspension in working, i.e., it doesn't flocculate and go dormant.
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Old 05-13-2006, 04:44 PM   #22
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Ok, here is a 'mini-tutorial' on how to build one of these. This should get you pointed in the right direction. I'll just reuse the pics from the first posts. Let me start out by saying that this is not my idea, but rather my take on this excellent project. Since I was going to be doing yeast starters anyhow, and I had 95% of the parts already I thought I'd give it a go.

The idea is that a yeast starter that is fermented on a stir plate will yield a substantial larger amount of viable yeast then a non-stir plate starter. This is because the yeast are kept in suspension and not allowed to flocculate by the stiring process. The stirring may also aid in airation of the yeast.

What you need:

1) 12V DC fan.
2) a few rare earth magnets.
3) something to control the speed of the fan.
4) a 12 v AC-DC power supply (wall wort)
5) stirbars
6) something to 'hold' it all.
7) misc bolts etc.
8) (optional) switch and LED

For the fan, I used a 120mm 12v DC pc case fan. You can probably use a 90mm or a 80mm fan but they are smaller. The magnets are placed on the fan hub so i like the 120mm fan better bacause the hub is larger and the magnets can be placed farther apart. You DO NOT need a high power fan, in fact don't want one because the speed the fan spins is too fast and you need to slow it down even for a low power fan. You can also buy fans that already have a speed control at some PC mod sites or stores.



Now for the container. I used this Project Enclosure from radioshack. Its perfect for a 120mm fan and this project. Its 8x6x3 and provides a good platform for even a 2000ml erlenmeyer flask.



You can get rare earth magnets at mcmastercar or at any science surplus store, but a great place to get them is from old hard drives. I ripped open a few old hard drives and stole magnets out outa them. They are on the arm of the read/write head. They are usually glued on and you may have to wack them with a hammer and screwdriver to get them out. They are SUPER strong magnets and will stick together really tight. Careful and don't get your fingers pinched in between them. I used epoxy and glued 2 together and then glued them as far apart as I could to the hub of the fan. (center them as best you can so as not to upset the spin of the fan.) I placed one north side up and one north side down.



I placed the fan hub facing up centered on the lid of the project box and marked the fan holes. Then I drilled 4 holes though the lid. I then put 4 #10 2.5" machine screws through the lid with the head sticking out on the outside. I then tighted a nut on them. Next, I spun another nut on each bolt down about 1 inch from the bottom. The fan went on next, followed by another nut. You can now adjust the height of the fan by moving the nuts up or down the bolt. You will want to adjust it so that tihe magnets are as close to the top of the enclosure as possible without touching. Note: When I say top I really mean the bottom section of the enclosure because the enclosure is placed upside down when it it complete and operating.

This is what it looks like.

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Last edited by MrSaLTy; 05-21-2006 at 10:21 PM.
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Old 05-13-2006, 04:45 PM   #23
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Speed control. This is the meat of the project right here. You can use a rheostat or a potentiometer to adjust the speed if you like but it may be difficult to control it this way. You may get a very small amount of adjustment or you may have to use a 6v power supply to get the control to spin slow enough for our purpose. You can also get fans with variable speed controls from PC mod shops etc. If you want to just go with a rheostat get a least a 3 watt 20-50 ohm rheostat.

Here is a how to.....

http://www.bit-tech.net/modding/2001...control/1.html

I chose to go with a simple LM317 voltage regulator circuit. Schematic here.



This circuit can vary the voltage from about 1.3V to just under 12v I recommend this if you have a little electonics knowledge and know how to solder. Here is an EXCELLENT tutorial on how to build this circuit with component placement and everything. I have a list of parts etc at the end of this post.

http://www.rigacci.org.nyud.net/docs...rial-full.html

I put a power connector jack in one end of the enclosure to to connect the power supply. Then ran the power to a switch on the other side. Then to the circuit, which outputs to the fan. I also added a LED to show when it is on. The adjustment knob is attached to the potentiometer from the lm317 circuit or your rheostat. Here is the guts of the stirplate. You can get along fine without a power indicator LED or even a switch for that matter. you can just plug it in to turn it on. Make sure the power connector you use matches the size and polarity of your wall wort power supply.



And a closeup of my circuit.

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Last edited by MrSaLTy; 11-05-2009 at 04:45 AM.
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Old 05-13-2006, 04:46 PM   #24
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I also placed a small rubber adheasive 'foot' to each corner of the bottom to absorb vibration and and to hold the stirplate in place while its in use. It is operated 'upsidedown' with the lid of the project box facing down and the fan inside facing up. This way, the magnets are right near the surface of the plate. Also with the lid near the bottom there is less chance that an overflow of yeast can spill out and get inside the box. I have used the stirplate once so far with great success. I used the 1 3/8" x 1/4" stirbar as it seemed to work better.


Action shots:





Where to get parts: First a note about passive components. (resistors, capacitors etc) You can get most of this stuff a radioshack but you will pay WAY more for them there then any other decent electonics store. Here are most parts at radioshack:


Project Enclosure 8x6x3" 270-1809
Size N Panel-Mount Coaxial DC Power Jack 274-1576
12V/500mA AC-to-DC Power Adapter 273-1773

lm317 circuit parts
TO-220/TO-202 Aluminum Heat Sink 276-1368
10K-Ohm Linear-Taper Potentiometer 271-1715
Adjustable-Voltage Regulator LM317T 276-1778
1K Ohm 1/4-Watt Carbon Film Resistor5 Pack 271-1321
0.1µF 50V Hi-Q Ceramic Disc Capacitor Pk/2 272-135
Dual Mini Board with 213 Holes 276-148
Radioshack site did not have the polorizaed electolytic caps needed though they may have em in the store.

A real good place to get electronics is http://www.jameco.com/ Here are some of the circuit parts there.

Ceramic Disc Capacitors ,.1uF 15270
ALuminum Radial-Lead Electrolytic Capacitor 1uF
LM317T IC 23579
Linear Taper Potentiometer 10k ohm 255521
1/4-Watt Carbon Film Resistor 1k ohm 29663

They also have about a jillion LEDS, switches and wall wort power supplies a much better prices then ratshack.

You can also find all this stuff at mouser electonics.

http://www.mouser.com/

You can get stirbars, Erlenmeyer Flasks and probably magnets at Cynmar.

http://www.cynmar.com/


1-3/8 In. X 1/4 In stirbar

2 In. X 5/16 In. stirbar

You can also get stirbars, magnets and just about anything else under the sun at mcmaster carr.

http://www.mcmaster.com/

You can also get a stirbar at BEER, BEER, and More BEER.

replacement stirbar

Good luck!! LEt me know if you have question and I can try to help if I can. If you really need detailed pics, let me know and maybe I can snap a few more.

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Last edited by MrSaLTy; 05-21-2006 at 10:23 PM.
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Old 05-15-2006, 05:49 PM   #25
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Hmmmm.... 2 days and no replies... is this not what you guys were looking for? Do I need to change something?

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Old 05-15-2006, 05:57 PM   #26
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Looks great! Somehow I just missed this post. Glad you bumped it.

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Old 05-15-2006, 06:35 PM   #27
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Can you just go straight through the rheostat without making the circuit? Or would I start a fire that way?

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Old 05-15-2006, 07:09 PM   #28
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I missed this post somehow too. Thank you SO much! I have about half of this stuff hanging around the house already, so this should be a lead pipe cinch.

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Old 05-15-2006, 07:31 PM   #29
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Quote:
Originally Posted by jerly
Can you just go straight through the rheostat without making the circuit? Or would I start a fire that way?

Yes, you can just use a rheostat, many do. They do get pretty hot though. You may have to use a lower voltage Power supply to get it to slow down enough for you. Also, you may have to fiddle with different values because some may not give you a very wide adjustment. I'm not totally sure because I did it a different way. There is a link up there in the section about speed controls to a site that tells how to add a rheostat to a fan.
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Old 05-17-2006, 05:01 PM   #30
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How many magnets can you get out of an old hard drive?

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