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

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Anthony_Lopez

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So, I figured with the number of older stirplate threads with dead links as well as the multitude of questions I have seen regarding how to actually make one, I would cover the subject with my own. I made one that is cheap, easy to build, and requires nearly ZERO technical knowledge of electronics.

Disclaimer: DO NOT WORK ON LIVE CIRCUITS. Your power supply should not be plugged in until you have completed the construction of this SPECIFIC build CORRECTLY. Electricity can kill you, regardless of the voltage applied.

Your "Cheap and Easy" Stir Plate:

[ame=http://www.youtube.com/watch?v=U9HOt9BRrlI]YouTube - Homemade Stir Plate[/ame]

Parts:
-I used a 6 volt Cell Phone charger as my power supply. Most of us probably have gone through a few cell phones over the last couple years, and just about any one should work in the 5-12 volt DC range. (They are all DC current)
-4 inch computer fan. Mine was 12 volts DC.
-hard drive magnets. I only used one. You can also buy rare earth magnets online from a number of vendors. Neodymium magnets are cheap retail if you can't find an old hard drive to scrap.
- 2 inch diameter steel washer.
- Some scrap wire will be helpful, however we'll only need about a foot of black and red wire.
I got all of the above parts for free.

If you can't source hard drive magnets, I would suggest checking out K&J Magnetics. I used these. When ordering from them, be sure you pay attention to the thickness of the magnet, since most of what they offer is magnetized through the thickness measurement.

From Radio Shack, you'll need the following:
7" x 5" x 3" Project Enclosure: Part Number 270-1807 - $5.99
25 ohm 3 watt Rheostat (aka Potentiometer): Part number 271-265 - $3.99
12 Volt DC/30Amp Rocker Switch with LED - Part Number 275-018 - $3.99
Silver Tone Knob - Part Number 274-424 - $2.99

Part Totals: $16.96

If you aren't soldering friendly, you'll also need to pick up:
3/16" Fully Insulated Quick Disconnects (16-Pack) - Part Number 64-3134 - $2.19

Apparently the design of the rocker switch may have changed, so as of 9-30-09 try these disconnects instead:
1/4" Fully Insulated Quick Disconnects (10-Pack) - Part Number 64-4040 - $1.99

That brings us up to about 19 dollars total.

I tried to make sure that all parts that I purchased were easy to come by at a Radioshack so that people won't have to substitute.

From the hardware store, we'll need (4) 2.5 inch 10/32 bolts), 12 10/32 nuts, and 4 washers to fit the 10/32 bolts.
Please Note: A 10/32 Bolt designates a size #10 with 32 threads per inch. You can also choose #10-24 bolts, but make sure you use the correct nuts. A 10/32 bolt is NOT a 5/8" diameter bolt.

The most important part of all of this is using the steel washer. By gluing the washer to the fan, you are adding magnetic point for your magnet to stick to without gluing it. This will allow you to fine tune the plate before gluing down your magnet (They won't come off very easily once glued) Also, if you decide that you want to use a larger or smaller stir bar, you can add or remove magnets and center them correctly without having to scrap your fan.



I drilled my holes for the potentiometer and the switch on the 5" x 3" side of the project enclosure to allow for more mounting space for the fan. Mount them up using the enclosed hardware that came with both of them. I also drilled a hole on the bottom corner of the enclosure to run the power supply out of the box.


Wiring Overall View

First things first: Wiring-

Get your Black and Red computer fan wires stripped. If you aren't soldering, put a female quick disconnect onto the Red wire.

Next, cut off the power supply “phone” side and try to keep the power cord going to the wall socket as long as possible. This just makes things easy if you make a mistake. Some phone chargers will have two wires, while others I've found have a “braid” going around another insulated wire. The “braid” is our ground or negative and the inner cable is your power side. For the chargers with 2 single wires inside, black is your ground.

Strip about 1/4” of the insulation off your wires. Take the black cable of your computer fan and the black cable of your power supply and twist the exposed wire together and insert them into one of the female quick disconnects. Make sure that you have already put your power supply cable through the hole you drilled in your enclosure before making this crimp or you won't be able to close your enclosure when you are done. Connect these two wires to the “Earth” male connector on your power supply.

Now, take your Red cable from your power supply and add a female disconnect onto this cable and attach it to the “male” terminal on your power switch labeled “Supply”

We are ALMOST done with all the wiring. The only male terminal left on our power switch is the one labeled “Load”. Take some of the spare wire, about 4-5 inches, and strip off the insulation from each end. Attach a female disconnect to each end. Now, attach one side of the wire onto the “Load” terminal on your power switch, and the other to the center pin of the potentiometer.

The last step is to take the “Power” cable (red) from your computer fan and attach another female disconnect. Attach this disconnect onto the right side pin on the potentiometer.


Potentiometer Wiring
 
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Anthony_Lopez

Anthony_Lopez

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Power Switch Wiring

Assuming everything has been done correctly, plug in your power supply, flip your power switch to the “On” position, and try turning the knob on the potentiometer back and forth. You should be able to observe the fan speeding up and slowing down as you turn the knob back and forth.

Now, we need to take the steel washer and glue it onto the fan. I used some 60 second epoxy so that I could turn the fan on and off to observe if the washer was centered on the center of the fan.

The next steps in this project is to fine tune the positioning of the fan within the enclosure, and try magnet combinations and positions until you get your bar spinning correctly.

I used 2 ½ inch 10/32 bolts with matching nuts and washers to mount my fan. I also used some ¾ inch stand offs to raise the fan. Instead of the standoffs, you can use extra 10/32 nuts to position the fan up and down the bolts. I also found that you need to drill out the holes of the fan to get the bolts through. 8/32 bolts will work without drilling.


Mounted Fan



Bottom Side of Aluminum plate with fan mounted and secured.

Your project enclosure should have come with both an aluminum and a plastic sheet to close up the enclosure. I drilled out the pattern for my fan's mounting holes into my aluminum sheet, and then mounted the fan. Once I had everything drilled out and mounted, I put every thing together, and tried it out...

Good Luck!!!

Also, for all you other DIY'ers, let me know if you catch a mistake or typo on here so I can edit...
 

slimer

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A little fyi, if you are retiring a computer, many have rocker switches on them. I used one for my stirplate.
 

jpowers1

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Any thoughts on turning the plate on and off with a starter? I'm pretty sure I can build these for free quite easily, but I understand they make some noise. I live in a dorm, so I'm not going to sleep a few feet away from it running. Do they make much noise, and would it greatly effect the starter if it were still for 7 hours or so, then turned back on?
 
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Anthony_Lopez

Anthony_Lopez

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As for starters, I'm not completely sure what the effects would be. They don't make much noise IMO, however I work in a vibration lab and I spend about 8 hours a day listening to the equivalent of a jet engine...
 

boyurboy

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Just out of curiosity, how did you get the magnets out of the HDD? I took one apart earlier this week, and it appears that the magnets are epoxied to a metal plate. I am assuming that the magnets you are talking about are the ones that support the arm in the drive?

Edit: Figured it out on my sacrificial drive....there was a layer of adhesive, but it was not epoxy like it appeared. Was able to crack it with a longer screw in the mounting hole that was below the magnet.
 

Revvy

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Brian,

Nicely put together tutorial and a real good job on a cheap stirlplate. I like that you thought of the solderless connects/disconnects for those with little comfort in soldering.

:mug:


*prosted this thread as well*
 
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Anthony_Lopez

Anthony_Lopez

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I'm Tony... Brian is the other "NO CLUE" brewer. We like to confuse everyone as much as possible...
 
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Anthony_Lopez

Anthony_Lopez

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As for removing the magnets from the bracket, I put the bracket in the bench vise, and gave the edge between the bracket and the magnet light taps until the coating over the magnet lets go. Just be careful trying to pop them off... They are quite easy to break.
 

boyurboy

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Thanks! I figured mine out with a little bit of thought. The metal plates the magnets were adhered to had mounting holes that I could drive a correctly sized bolt through to break the seal and the magnets hold to the metal beneath.

Awesome tutorial. This might get build this weekend.
 
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Anthony_Lopez

Anthony_Lopez

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Just be careful using that method as the magnets will break easily if you apply too much force through them. Hitting them from the side works every time.
 
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Anthony_Lopez

Anthony_Lopez

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As for the stir bar, my LHBS only had a 1" bar. I'm waiting to get my 2" bar to test it out with that one... With the 1", it spun quite well, however I'd like to pull the cone further down the flask, which should be easy with a 2".
 
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Anthony_Lopez

Anthony_Lopez

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Our Avatars don't help either... It was from our first yeast pitch into our first home brewed beer... Thats back when we weren't adjusted to the smell of boiling wort...
 

Ogdenenator

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One change i would make to your wiring is to connect the middle terminal on the Potentiometer to the unused one. all this would do is allow the stir plate to function if the Potentiometer fails. It would run with no resistance - AKA full speed

I am having trouble getting my fan placed in my housing, the fan has a bit of give to them so it pulls up and hits the inside of my case. I'm sure ill figure it out at some point.

Thanks for the build instructions
 
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Anthony_Lopez

Anthony_Lopez

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Is the fan from a computer? If you look at my pictures, using the 8/32 or 10/32 bolts should keep it from moving around. If you are using a similiar project enclosure, I would suggest drilling out the hole pattern in the aluminum plate to give some more rigidity to your enclosure and fan.

Good luck with the project!
 

tdiowa

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Thanks alot for your specific instructions. Just finished mine and the stir plate works like a charm. Only thing I did differently was tinker with the height of the fan.

Again thank you for you patient and your dedication to share information.

Cheers.
TD
 
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Anthony_Lopez

Anthony_Lopez

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The fan placement will always vary depending on where you get your magnets from. Glad to hear it worked out for you!
 
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Anthony_Lopez

Anthony_Lopez

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Thanks Mang! Last night I got about 25 magnets from my buddy... We are working on getting more fans and cell phone chargers right now. I also found that many Linksys routers have an acceptable voltage rating for this application.

I've also started working on building one using a hard drive motor...
 

mthompson

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I roughed one of these things up last night from my electronics parts box. I got it to work with a few different controllers, but none of them were very 'fine-tuned' for speed control. I will have to get the one in the OP perhaps.

The other main problem I had, was when I put most of the HD magnets I have on the fan, they are too strong and prevent the fan from spinning. I got two small magnets from one drive...the fan spins with one but not both on it....but one magnet is not strong enough to attract the stir bar with any gusto. Anyone else have this problem?

I have a few other fans I could try, but would also like to keep some intact for computer use. Are all fans created equal? Or, do some fans have less metal inside of them?

Thanks for any help y'all can give me.
 
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Anthony_Lopez

Anthony_Lopez

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I would say that not all fans are created equal. I have been using fans out of Dell's since that is what we use at work. The best placement I could get was with one magnet in the center of my fan.
 

mthompson

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Guess I'll have to try a few others. The one I used last night was new in the box (from 3 years ago) and was where the rest of the supplies were - so I used it. It is one of those fancy lighted ones that is clear plastic. I'll try one of the plain ol' black ones in some cases I have lying around tonight.

Any suggestions for solving the magnet strength problems? I am gonna try another stir bar on the fan....they seem strong enough to spin the other bar, but not strong enough to stop the fan from spinning. I was also wondering if there was a way I could shield the fan from the full magnetic force of some of these magnets. Would a large metal washer aid in this?

Thanks,
 
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Anthony_Lopez

Anthony_Lopez

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The reason I use the stainless steel washer is to allow me to move around, add, and remove magnets if I need to in order to fine tune my stir plate...
 

mthompson

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I read that above, was just curious how well that shielded the fan's innards from the magnet, cause I think that is my biggest problem right now.

I think my plan is to get two earth magnets fro radio shack when I get a 25ohm rheostat and then use the stir bar with magnets attached to set the positions/spacing correctly on to the outside of a 1.5" washer glued to the fan.

I think that will work in tow ways....allow for flexibility in washers and set the magnets on the outside rim of the fan motor housing.

Thanks,
 

planenut

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I am working on one of these right now.

I was surprised to find out that my fan has a dedicated positive/negative power wire. I thought reversing the wires would ran the fan in the opposite direction but not with mine...

Also my magnets may be a little weak, it will spin with the 6 volt supply (not fast enough) but throws the bar with the 12 volt supply. I can't wait to see if the rheostat solves this problem.
 
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Anthony_Lopez

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The rheostat will allow you to fine tune your fan speed. Hopefully that helps your setup
 

undallas

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thanks for the post... I just made one today after I stopped by the Shack to get some supplies...
amazing, I just paid $6 and I got a stir plate by using scrap PC material.
LBHS sells one for $50.

Now.. I just need to wait for my stir bar to get in...
I have been hand swirl my pacman culture for 4 days now...
the yeast is amazing.... it really grows on you.
 

mthompson

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-Update-

All fans are definitely not created equal. I tried a black case fan, it works on everything but the one huge HD magnet I have.....so I'll most likely use it unless I can find a 120mm.

I also tried a pci blower-style exhaust fan that I have. This thing would fling the huge HD magnet off of it.

It is only 12v and 0.16A, but is uses ball bearings and is a bit beefier....perhaps I'll use it if the other won't work through the housing.

I am planning on picking up the parts I am missing on Friday. I'll update after it gets finished.
 

cyberbackpacker

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Since I will be scavenging an old pc tower for parts anyways, could I use the power supply from that in lieu of the cell charger type? If so, I am assuming the rheostat would then let me fine tune how much "oomph" I give the fan...
 
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Anthony_Lopez

Anthony_Lopez

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I haven't tried using a computer power supply. I would expect the output to be a little higher than what is required to run the fan.

Thus far, I have used:
Cell Phone Chargers, Bluetooth Headset chargers, and Linksys Modem Power Supplies.
 

camiller

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Since I will be scavenging an old pc tower for parts anyways, could I use the power supply from that in lieu of the cell charger type? If so, I am assuming the rheostat would then let me fine tune how much "oomph" I give the fan...
If it is a very old computer it would be easy enough, if it is just old and is a ATX power supply then there are a couple pins you have to short to make it work, otherwise the power supply doesn't think it is connected to a motherboard and wont turn on.
 

Deacon1856

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I got all the parts for this and just spent some time in the garage putting it together. Unfortunately I cannot get the fan to speed up and slow down. One speed. I've got it wired properly I believe, but the speed control is a no go. Any suggestions?
 
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Anthony_Lopez

Anthony_Lopez

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If you are getting voltage to your fan, and it is wired through your potentiometer, I would make sure that you have your power output or "load" from your power switch going to the center pin of your potentiometer, and the power lead from your fan going to your right pin of the potentiometer.

Please note, when I say "right pin" i'm assuming you are looking at it from the pin side and not the "knob" side
 

DrewsBrews

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I started building one of these a while back (based on another thread) with similar parts. The only problem I noted was that the rheostat didn't seem to give much variability as far as speed control goes. For a third to half of the range of the rheostat the fan doesn't move. Turn it a little further and the fan comes on and jumps up to what appears a decent RPM, but turning it all the way only increases the fan speed maybe 15-20%. I'm not particularly electrically inclined, so I'm wondering if someone might suggest ways to correct the problem.

One thing to mention: this happened without any load on the fan. Would a stir bar in a flask full of liquid provide resistance to make the speed more controllable? I never got around to finishing it so I can't test the theory.
 
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Anthony_Lopez

Anthony_Lopez

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Inside a starter, there will be more resistance on the stir bar than when you try it out with water. You can go with a higher rated rheostat and try that out to see if it can give you a more variable speed. The rheostat is essentially a variable ohm resistor. Another factor is the power supply you are using. Most computer fans are rated at 12 volts DC, while most cell phone chargers are rated at 5-6 VDC.
 
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