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Old 07-27-2012, 05:51 AM   #1131
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Quote:
Originally Posted by r8rphan

a) In every picture I see of a computer fan, there are bars connecting the frame of the fan to the motor in the center. this makes sense as the thing has to be mounted some how... Do the fans typically have these on both sides or do I have to find one with them on only one side? IF so, how do I do this seeing as nobody seems to show pictures of both sides? Or is it okay to cut the frame connecting bars away on one side?.. Or better yet can someone point me to an affordable one that is 'recommended' for this purpose?
They usually have them on just one side. I doubt it matters, though.

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Originally Posted by r8rphan
b) What size stirrer should I get.. I was going to get one that was 1" long with a rib in the middle... is that large enough?
I've found that my 1" stir bar is ok for 1L starters but 2L starters need a 2". I'd go with a 2".


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Originally Posted by r8rphan
PS.. my plan is to make a wood disk with a perfectly centered recess to hold the magnet (I have a CNC router) and mount that on the fan... I was also planning on carving the box out of wood... how is the wood disk (steel washer in the original post) attached to the fan.. silicone? and what is the optimal distance the fan magnet should be from the bottom of the flask?
Mine is super-glued. Closer is better, mine is about 3/4" from the top of the plate and works fine.


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Old 07-28-2012, 04:08 PM   #1132
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Just finished building mine! I ended up using a 90mm fan with a 12vdc power supply. I made my own stir bar and the whole assembly works wonderfully. I had to make some "modifications" to the fan, however. The fan would not sit high enough for good contact so I cut the 4 top screw holes off to give me some added height. I used nuts to adjust the height accordingly after that. Thanks for the article!


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Old 07-28-2012, 06:36 PM   #1133
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Originally Posted by brewinitup View Post
Just finished building mine! I ended up using a 90mm fan with a 12vdc power supply. I made my own stir bar and the whole assembly works wonderfully. I had to make some "modifications" to the fan, however. The fan would not sit high enough for good contact so I cut the 4 top screw holes off to give me some added height. I used nuts to adjust the height accordingly after that. Thanks for the article!
how did you make a stir bar?
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Old 07-28-2012, 06:44 PM   #1134
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I just used a set of 5/16" rare earth magnets from radio shack and put them inside an inch of 5/16" ID vinyl tubing. I capped off the ends with cut pieces of a 5/16" nylon bolt that I sealed internally with epoxy. It may not quite match the typical stir bar, but it stirs wonderfully.

Edit: I should also note that I already had the magnets lying around for another one of my nerdy hobbies. Otherwise, it would be cheaper to just by some stir bars.
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Old 07-31-2012, 10:22 PM   #1135
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Quote:
Originally Posted by Mellow52 View Post
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!
I just purchased the parts in the original post, but this puts the heat dissipation on the LM317T right? (AFAIK, the LM317T turns the excess power into heat for current regulation)? LM317T's are typically inefficient, but they can handle the heat fine when you heatsink them. I'm considering returning my parts and going this route.

Please correct anything I said that is not correct, it's been a while since I worked with the LM317T and my circuit may have been a bit different.

For the money all of these additional parts would cost, would I just be better off buying a stirplate?
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Old 08-02-2012, 09:47 AM   #1136
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Originally Posted by Justintoxicated View Post
For the money all of these additional parts would cost, would I just be better off buying a stirplate?
Since some of the parts comes in packages of two or more, I just ended up making 2 stir plates and gave one to a friend! But yes you will need some sort of heat transfer from the LM317t. You can cut some copper or aluminum plate and drill a hole and screw it to the LM317t with some thermal paste. I ended up snapping the piece of copper I had and ended up purchasing a tiny aluminum one from radio shack. (http://www.radioshack.com/product/in...tent=CT2032230)
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Old 08-02-2012, 04:48 PM   #1137
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Originally Posted by rpryor View Post
Since some of the parts comes in packages of two or more, I just ended up making 2 stir plates and gave one to a friend! But yes you will need some sort of heat transfer from the LM317t. You can cut some copper or aluminum plate and drill a hole and screw it to the LM317t with some thermal paste. I ended up snapping the piece of copper I had and ended up purchasing a tiny aluminum one from radio shack. (http://www.radioshack.com/product/in...tent=CT2032230)
Funny, I just found one of those in my spare parts drawer. The local RS does not seem to carry those heatsinks it anymore.

My soldering iron ran out of butane last night or I would have finished. The LM317T did not even get warm after 1/2 hour of testing so i'm thinking it will work fine without any heatsink (at least for the fan I am using now which is only consuming about a watt of power). I did not bother to buy one of those blank circuit boards for this project although I think it would have made things easier. My LM317T is lose in the box but I will eventually hot glue it.

My only other mistake was using a switch that has a burned out LED So I ordered a new fancy one from DX to make me feel better. I already have a 3/4th inch hole drilled into the box. Just hope it fits in the box (It should as I purchased the largest project box RS had).

http://www.dealextreme.com/p/car-swi...102125?item=32

It took a lot longer than I anticipated (because I am careful to lay things out as I want them and get everything centered, and wires carefully twisted) but wasn't hard by any means.

My RS did not have the exact capacitors or resistors. I used 2 470 ohm 1/2 watt resistors in parallel with one 10 ohm 1/2 watt in series, because I already had these laying around from YEARS ago. Seems to work fine although it would make more sense to use 1/4th watt 470's with a 1/2 watt 10 ohm, or a 1 watt 10 ohm with the 1/2 watt 470's. I don't think it will matter much in this case as the components are probably overkill already.

I used a 22uf cap and a 4.7uf cap since thats what ratshack sells.

I also cut the shaft of the 5k pot so I could add one of them fan cy $4 knobs (well they only come in a packet of 2). My cost is up a little, but I can vary the fan from 0 RPMs to full speed with a 12v power source.
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Old 08-03-2012, 01:19 AM   #1138
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I made 2 stir plates based on the original post and both work fine, but I have some questions based on what others are doing:

1) why use resistors, capacitors and the LM317T? I didn't and my stir plates work. I just wired up an on/off switch and a pot and the fan.

2) does anyone have a good fan recommendation? I took both of mine from old computers. One came from a Mac and is clearly better-made and has no trouble spinning a 2" stir bar in a 2L starter. The other is a cheapie from a crappy PC and can only spin the 1" stir bar in a 2L starter - the 2" bar can stop the fan from spinning! I tried a third cheapie fan and it's no better, maybe worse.
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Old 08-03-2012, 08:23 AM   #1139
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Quote:
Originally Posted by troyh View Post
I made 2 stir plates based on the original post and both work fine, but I have some questions based on what others are doing:

1) why use resistors, capacitors and the LM317T? I didn't and my stir plates work. I just wired up an on/off switch and a pot and the fan.

2) does anyone have a good fan recommendation? I took both of mine from old computers. One came from a Mac and is clearly better-made and has no trouble spinning a 2" stir bar in a 2L starter. The other is a cheapie from a crappy PC and can only spin the 1" stir bar in a 2L starter - the 2" bar can stop the fan from spinning! I tried a third cheapie fan and it's no better, maybe worse.
1) The LM317T allows more control over RPM and depending on the fan can better handle the power dropped, especially if heatsinked. I can' t remember how to do the calculation, but essentially the resistors are wired to the LM317T to set it's current or voltage, where I am confused then is why they are needed when using a pot anyways. maybe it's to get a minimum voltage drop required. http://users.telenet.be/davshomepage/current-source.htm

A rheostat dissipates the power that is dropped as heat and will eventually burn up. Of course the amount of power dropped using it will depending on the current pull of your fan. For my .12 amp fan, it probably would have worked well enough, but with the circuit I have no I can change fans and still have full control without neededing to change power bricks.

I used a cooler master ball bearing fan, I would not use a cheapo sleeve bearing fan for this design. I used it only because it is what I had laying around but I too am interested on what the prefered speed of the fan is. I have some real nice Panaflo L1A (Legendary but no longer made) and L1BX's that I was tempted to use, but those are like $20 each. I have a few of them that have been running in my PC almost non stop for 7 years and have yet to show any signs of wear, while many other fans have been replaced several times. Hydro Sleeve bearing design seems very reliable from my experience and very quiet. They are quite stout and extra thick I just have a feeling that they would work perfect, unless of course super high speed is preferred. I guess they are a special sleeve bearing but they have outlasted all my ball bearing fans, and are easily my favorite PC fan. They look very plane are seem more industrial quality and less marketing than competitors in the same price range.

http://www.sidewindercomputers.com/pa12ulqu.html



stir plate by Glamisduner, on Flickr


stir plate by Glamisduner, on Flickr


need my stir bar by Glamisduner, on Flickr

The larger size project box holds a 2L flask nicely.

Unfortunately I think the switch I ordered off deal extreme is going to be too deep to use so I will need to order another one, it might fit depending on if they measured to the ennd of the leads or not. Going to be close though! The switch I have on there now does not have a functioning LED, since it burned out when used for another project. My problem now is that I already have a 3/4th inch hole. I know I had more of these somewhere but I seem to have misplaced them some time ago.

My Local Home Brew shop has 1" stir bars but they want $12 each for them so I think I'm going to order them online.

* NOTE TO OTHERS
If I was going to build another one of these I would put the switch and knob on the wider side of the box, that would avoid clearance issues with the switch being too long and hitting the bolt that holds the fan.
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Old 08-03-2012, 04:54 PM   #1140
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I grabbed an old 42V fan that wasn't being used at my work today, it measures 120mm. I also picked up a potentiometer than only says 4 watts, 10k ohm on it. Would this still work with this fan? I know the fan is overkill, but its $8-10 I can save by not buying a new one (don't have an old computer laying around). If I use a 12V power cable and a 12V switch, would it just limit my fan to this voltage, essentially making it work as a 12V computer fan?

Lol, I didn't look at the rating of the switch when I picked it up from work... it says 3A, 125VAC, and 1.5A, 250VAC

Also, in the center of the fan, there is plastic on one side, and metal on the other. The magnet sticks to the metal side... would I be able to keep it there, and have that side facing the top of my stir plate? Or will the fan not run properly? I'm guessing the stainless steel washer is being used to shield the magnet from the magnet in the DC motor (which I'm guessing this metal center is)... so is it best if I glue on a large washer to the side with the plastic center? and then glue the magnet on to the washer?


Thanks!


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