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Old 08-04-2012, 01:54 AM   #1141
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Originally Posted by JayMac
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?
Not quite. Reducing the voltage will slow down the fan. At a certain point, it won't have enough voltage to start up.

SOME fans (ie one that has a higher startup voltage requirement than its minimum voltage requirement) can be "helped" along by applying the power to it and manually giving it a quick spin to get it started (kinda like a rolling start with a vehicle). Obviously, operating it like that isn't really conducive to its use in a stirplate.

And even then, there will be a minimum voltage at which it will be able to CONTINUE spinning. 12V is probably below that minimum voltage - to give some perspective, it's like operating a 12V fan a 3.4V. I have never personally seen a 12V fan able to run at that kind of voltage.

And EVEN IF ONE COULD, it would be so close to its minimum voltage that speed control would be practically non-existent. Let's say that this fan had an astonishingly low voltage at which it could startup and maintain spinning of 3.0V. The minimum to maximum would therefore be 3.0V to 3.4V, meaning you have a usable range of 0.4V - or roughly 3% of its voltage rating. That's essentially negligible when it comes to controlling the RPM. Scale all these things up by a factor of 3.5, and you can say the exact same thing about a 42V fan.

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I'm guessing the stainless steel washer is being used to shield the magnet from the magnet in the DC motor
Not really. It's just to make it easier to position it well. Trying to fine tune the placement of one neodymium magnet onto (essentially) another one is not an easy thing, and can really hurt if you're not careful!
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Old 08-05-2012, 09:30 PM   #1142
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Not quite. Reducing the voltage will slow down the fan. At a certain point, it won't have enough voltage to start up.

SOME fans (ie one that has a higher startup voltage requirement than its minimum voltage requirement) can be "helped" along by applying the power to it and manually giving it a quick spin to get it started (kinda like a rolling start with a vehicle). Obviously, operating it like that isn't really conducive to its use in a stirplate.

And even then, there will be a minimum voltage at which it will be able to CONTINUE spinning. 12V is probably below that minimum voltage - to give some perspective, it's like operating a 12V fan a 3.4V. I have never personally seen a 12V fan able to run at that kind of voltage.

And EVEN IF ONE COULD, it would be so close to its minimum voltage that speed control would be practically non-existent. Let's say that this fan had an astonishingly low voltage at which it could startup and maintain spinning of 3.0V. The minimum to maximum would therefore be 3.0V to 3.4V, meaning you have a usable range of 0.4V - or roughly 3% of its voltage rating. That's essentially negligible when it comes to controlling the RPM. Scale all these things up by a factor of 3.5, and you can say the exact same thing about a 42V fan.


Not really. It's just to make it easier to position it well. Trying to fine tune the placement of one neodymium magnet onto (essentially) another one is not an easy thing, and can really hurt if you're not careful!
Thanks! I guess I'll go buy a 12V fan from a local computer store. So you're saying I could just flue it right onto the center of my fan? If so, I'd rather due this, to make things easier.
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Old 08-05-2012, 11:58 PM   #1143
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I built my stir plate several weeks ago and it works ok, but I can't really get the speed that I expected out of it. As a matter of fact, if I bump down the potentiometer even just a little bit it stops turning. I'm using a 12VDC CCTV camera power cord and a 12V fan, but the current rating on the power cord is only 500mA.

I've ordered AC fans for my lagering chamber and they get lots of juice straight from the wall. It seems to me that my potentiometer would work just as well for an AC circuit, but I'm afraid that it's max resistance isn't enough to really even slow the fan. Has anybody built one of these with an AC fan?

Thanks,
Andy

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Old 08-06-2012, 12:04 AM   #1144
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I built my stirplate using a 12vdc fan and it works just fine. Obviously you could use a 120vac fan, but you'd need to get a new potentiometer and rocker switch. You really don't want to use 12vdc equipment on a 120vac circuit.

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Old 08-06-2012, 12:10 AM   #1145
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I built my stirplate using a 12vdc fan and it works just fine. Obviously you could use a 120vac fan, but you'd need to get a new potentiometer and rocker switch. You really don't want to use 12vdc equipment on a 120vac circuit.
That's what I suspected. I imagine it's not rated for that kind of current and it will burn it up. Thanks!
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Old 08-06-2012, 06:56 AM   #1146
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That's what I suspected. I imagine it's not rated for that kind of current and it will burn it up. Thanks!
You could use a dimmer switch to adjust the fan. Just be careful when dealing with direct 110v!
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Old 08-06-2012, 09:00 AM   #1147
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You could use a dimmer switch to adjust the fan. Just be careful when dealing with direct 110v!
I wouldn't use a typical dimmer for this, if for no other reason than that it's going to make a really annoying buzzing sound (has to do with how it alters the voltage sine wave). I would go with a switch that is *intended* for adjusting fan speed.
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Old 08-10-2012, 08:55 AM   #1148
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So my stirbars came in. I got a 1" and a 1 and 3/8th inch. I think I like the 1 and 3/8th inch better but please advise.



Not sure why I would need to turn it down, perhaps it will ferment too much and need to be slowed down?

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Old 08-10-2012, 03:54 PM   #1149
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I started a 3L starter last night of Wyeast German Ale 1007 in my 5L flask. This morning I looked at it and it had developed a thick Krausen and almost blew out the top! Be careful with the 2L flask in the video...

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Old 08-10-2012, 04:29 PM   #1150
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Quote:
Originally Posted by Justintoxicated
So my stirbars came in. I got a 1" and a 1 and 3/8th inch. I think I like the 1 and 3/8th inch better but please advise.

Video Link: http://www.youtube.com/watch?v=huG9MVZspUk

Video Link: http://www.youtube.com/watch?v=RapsolLdp5Y

Not sure why I would need to turn it down, perhaps it will ferment too much and need to be slowed down?
It's my understanding that a big vortex is unnecessary, a small dimple is good enough. So either should be fine.
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