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Old 08-06-2013, 07:01 PM   #1
Alabamy
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Default Which potentiometer do I need for a stir plate?

I want to make $10 stir plate featured on the HomeBrewTalk home, but I would like to add a potentiometer to adjust speed. Mostly just because I think it would be cool. Ebay has several different types with different resistances. I was planning on using a 12-volt cell phone charger for the power source as outlined in the HBT project. Could someone tell me which potentiometer and knob I need? Any ideas how to combine these two projects? Would a child's pencil box work in place of the plastic sheeting or cigar box?

http://mad-science.wonderhowto.com/h...plate-0134284/

http://www.homebrewtalk.com/entries/...n-dollars.html


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Old 08-06-2013, 09:07 PM   #2
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Hey,

Best thing you can get for your box is an old cigar box. You should be able to call/visit a local cigar shop and they usually give those away for free. I got like 5, one for stirplate and the rest for storing things.

As for the potentiometer and knob, you don't really need a nob it's really just convenient and cosmetic. But the potentiometer I'm not positive about what their ratings or whatever should be. I have one that I got from a local electronics store that has 3 prongs on it and it doesn't have an on/off function. If it's plugged in, it's on. Id say take the charger to a local electronics store and ask them for what one would work for that power source.


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Old 08-07-2013, 04:40 AM   #3
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Default Potentiometer

I don't know that this is relevant to your question or not but in of the builds I saw he specified a 25 ohm one. Is that what you were asking for? I can try to find a link if that would help.
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Old 08-07-2013, 06:01 AM   #4
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I didnt bother with one, never could get it to start properly with one.

I just get my stir bar centered in my flask, put the flask on the stir plate and plug it in.

if theres too many rattles i move the flask around until its quite (thus centered).
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Old 08-07-2013, 04:18 PM   #5
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Quote:
Originally Posted by eharris8310 View Post
I don't know that this is relevant to your question or not but in of the builds I saw he specified a 25 ohm one. Is that what you were asking for? I can try to find a link if that would help.
If you could find it that would be great. I'm a bit worried about what to use with a 12 volt plug.
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Old 08-07-2013, 04:27 PM   #6
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I would just use a 6V power supply and the pot specified in the DIY stir plate build thread. I did and it works great.
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Old 08-07-2013, 04:28 PM   #7
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You want a pot that can handle several watts, and you only want some resistance, so 25k or 50k would be good. Anything more than that and it will just work like an off/on switch. Personally when I built mine I found a 5.5v 300ma power supply to provide the perfect amount of spin for a 1" stir bar, even in a 2L starter. I had played around with using some old guitar pots (think they were 500k, 1/4 watt) I had but I burnt one of them up pretty quickly b/c I had to use a 9v power supply with it for the fan to even spin.

Just remember that you just want a dimple in the top of the wort, not some huge vortex of death. You just want the yeast to stay in suspension and help oxygenate it.
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Old 08-07-2013, 09:51 PM   #8
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I can't post a link but look at stirstarters.com


He has a DIY page that shows the proper way to use a potentiometer to control the fan speed...I've heard people complain that it can catch fire potentially if used to dissipate too much current for too long...with that being said I didn't do it the "right" way myself, I use the potentiometer when getting things started so it doesn't throw the stir bar off, and then ALWAYS turn it up all the way after its going so the pot isn't having to work so hard.

Hope that helps!!
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Old 08-07-2013, 10:05 PM   #9
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There's zero chance that mine won't throw the bar unless I have it all the way down.

I think the fan inside helps keep the components cool.
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Old 08-08-2013, 01:24 PM   #10
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Quote:
Originally Posted by LovesIPA
There's zero chance that mine won't throw the bar unless I have it all the way down.

I think the fan inside helps keep the components cool.
I feel like I went through ten revisions of my stir plate before I got it all set correctly. Are you using hard drive magnets?? It is a million times easier to center a stir bar on a couple of disc magnets (that stir starter site has the type he was using, which I'm not affiliated with in any way). I bought mine from amazon and weren't too expensive at all. I can crank my 12v supply all the way up and it won't throw the bar...

It also helped to use a pencil to draw on the magnet while its spinning to find the center.


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