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MNBugeater 04-30-2008 01:52 AM

Homemade Stir Plate - Lessons Learned & Tips
 
I have read some of these at various locations and finished assembling a homemade stir plate with the common parts people can harvest from old computer parts, old cell phone, etc. This isn't a documented "How to..", there are plenty of them here that are excellent, rather a, "I did this, and heres something to do different, don't repeat my mistakes."

Thought I would put together my experiences while they are still fresh in my head and the blood blister on my finger is still throbbing. But as a side note, remember, this is REALLY cheap and easy and I would still recommend it if you make yeast starters. And if you don't make yeast starters.....start making yeast starters.

So the common parts needed simply put are:

Power Source - Cell phone charger, Computer power supply, or buy one at Radio Shack
Stir Plate - Computer Fan (most common)
Magnets - Computer Hard Drive (Rare Earth magnets)

Stir bar, Flask, Glass container, etc...easy to find online or LHBS

If you have an old computer lying around, you have everything to make this with little to no wiring necessary. The reason i like the power supply from a computer is that it is already wired to plug in fan or fans. No wiring needed, just plug in the 4 pin male to female connectors. Done. If you don't have an old computer, go to your IT department at work or large business. They either have a boneyard of old crap or they throw stuff out routinely. Ask for an old power supply, case fan(s), and a couple hard drives. It is entirely expected that they wont give you old hard drives, but ask if you could take it apart in front of them and get the magnets. Or even offer to drill a hole through the plates. This is what we do before we dispose of them.

The magnets. DON'T underestimate how powerful these suckers are. If you have two they WILL snap together so hard they will pinch your fingers. Like immediate blood blister pinch. The stupid part is I work in IT and I KNOW how strong these these are and despite my careful handling....DAMN...snap...ouch.

I used JB Weld to adhere the magnets to the hub of the fans. Let the JB Weld cure before trying to add another magnet. It isn't strong enough to hold against the force another magnet in near proximity.

I think thats it. Just wanted to tell another example of how easy it is to make these. All the parts are in a scrap computer. Have fun.


MNBugeater

Cookiebaggs 04-30-2008 02:37 AM

The best lesson's I learned were,

1.) One magnet centered on the fan hub is more than enough to grab the stirbar provided you have the magnet close enough to the surface of the enclosure box.

2.) A simple rheostat is all you need if you have an AC power supply that is adjustable to 1.5, 3, 4.5, 6, 7.5, 9 and 12 volts. If you need to slow down the fan, simply switch to a lower voltage. ACE Hardware had this AC power supply for $13. Not bad.

3.) Slide an O-ring from a dip tube on the stir bar and center it. It acts as a spin point and works well.

4.) Find out where people drop off their old PC's in your area. I went to our city recycle yard with a screwdriver and a side cutters and got fans, hard drives, and on/off switches for free.

http://inlinethumb15.webshots.com/36...425x425Q85.jpg


http://inlinethumb13.webshots.com/39...425x425Q85.jpg

http://inlinethumb09.webshots.com/36...425x425Q85.jpg

Yuri_Rage 04-30-2008 02:52 AM

Quote:

Originally Posted by Cookiebaggs
2.) A simple rheostat is all you need if you have an AC power supply that is adjustable to 1.5, 3, 4.5, 6, 7.5, 9 and 12 volts.

Best idea for simple speed control that I've seen to date!

derogg 05-01-2008 12:57 AM

What works best, spinning the bar faster or slower? Thanks - Dirk

ApolloSpeed 10-10-2008 09:31 PM

once again sorry for the noob boob.....but what is this for? Yeast starters? You just mix your starter and let it spin for a couple days?

Is that the only thing its for?

BarleyWater 10-10-2008 09:37 PM

Quote:

Originally Posted by ApolloSpeed (Post 890847)
once again sorry for the noob boob.....but what is this for? Yeast starters? You just mix your starter and let it spin for a couple days?

Is that the only thing its for?

Yep, helps the yeast grow by giving them more oxygen and keeping them in suspension. Search stir plate, and you will find more info than you will ever be willing to read through. Including my how to w/ pictures.

jimba009 10-10-2008 10:35 PM

WOW! I have been pondering starters. i know what i am doing in the morning!

rshosted 01-05-2009 04:18 AM

On lesson I learned is that a stir bar is needed (at least for me).

And two, is that I first used very strong magnets from a magentic nametag. They were likely earth magnets already attached to a plate. Problem was they were not 'reversed' or flipped so it was both positive sides up. My stir bar wanted one side but was 'afraid' of the other. When I replaced it with a hard drive magnet it worked like a champ.

Third, was not to put the magnet too close to the top of the box (on my plastic project box from radio shack). When I spaced it about 1/8 inch away from the top it spun faster and seemed to work better.

Good luck to others building.

Homercidal 01-05-2009 03:15 PM

For mine, I used a cast-off A-B printer switch for a housing. I mounted the speed control (simple potentiometer) right where the selector was, and the on-off right next to it.

There are likely to be many of these things floating around in IT departments collecting dust since everyone is now networking their printers instead of sharing them. Problem might be finding some that are not already thrown away.

Zymurgrafi 01-05-2009 03:39 PM

Quote:

Originally Posted by Cookiebaggs (Post 659955)
2.) A simple rheostat is all you need if you have an AC power supply that is adjustable to 1.5, 3, 4.5, 6, 7.5, 9 and 12 volts.

A simple model train transformer works well for me. Had several sitting around.


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