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How to build a stir plate for less than ten quid

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strange-steve

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I've been thinking about building a stir plate for a while and reading about the Brulosophy yeast starter harvesting method gave me a little push to do it. Being the miserable sod that I am, I like to do things as cheaply as possible, so this is how I built my stir plate for under a tenner. Actually it cost me about £6 but I had some stuff lying about the house which I was able to use.

So this is what you need, all available from eBay:

A 12 volt power supply - £2.19


A 12 volt PWM controller - £1.37


A 12 volt 92x25 mm CPU fan - £1.40


A couple of 8x5 mm neodymium magnets - £0.99


A handful of M3.5x50 screws and nuts - About a quid from local hardware store


Lastly you need an enclosure, this is where a little ingenuity comes in. I've seen these made from all sorts of things, cigar boxes, lunch boxes, tupperware, lego. Anything that is sturdy enough to support a couple of kilos will do, preferably non metallic because it'll interfere with the magnets. Google homemade stir plate for some inspiration. I used an old soap box which I found in the house. It's not quite as manly as those cigar box stir plates, but you have to admit it's pretty :D


If you can't find anything at home then an electrical adaptable box from B&Q will work well.

So once you have all the parts, mark the holes in the fan and PWM and install the screws through the base like so, this allows the fan to be height adjustable so that you can get the magnets as close to the lid as possible.


Drill a small hole for the power cable, cut the connector off, insert through the hole, connect to the "supply" side of the PWM. Connect the fan to the "load" side then mount both the fan and PWM.


Stick two magnets on the center of the fan, one positive up, the other negative up. I used gluedots to stick the magnets The center of the magnets should line up with the ends of the stir bar like so:


Put the lid on, plug in and switch on. If required adjust the height of the fan, the magnets should be nice and close to the lid without touching.


Test with stir bar in an erlenmeyer flask. I find it's best to turn the speed right down, switch on, then slowly ramp up the speed until it gets to where you want it. This is it in action:


So there you have it, a stir plate for about £6, and very pretty too :D

Edit to add: After a few uses I upgraded my stir plate from the soap box to a chocolate box. I found that the structural integrity of the soap box was becoming rather compromised. It was sagging a little in the middle meaning the magnets were rubbing on the inside making a very irritating sound. Also it wasn't waterproof, so I had concerns about the starter overflowing onto it. I also couldn't get rid of the lavender smell from it which was annoying when trying to have a sniff of the starter. The new one isn't as pretty but much more sturdy and made of plastic so should last a bit longer.



 

strange-steve

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I just shake it up. The Duran bottle was my fault as i forgot to loosen the cap but a 2l bottle is nice for a starter. I always chill and decant mine after tasting some of it. Have you tried it?
Yeah I used to use the shake method all the time for my starters and it works great. I don't think a stir plate is at all necessary for making good beer. However with the overbuilding/harvesting method I've started using, a stir plate makes the starter and harvest volumes more manageable.

For example for my next brew with an overbuild of 100B cells using a stir plate the starter volume is 1.9L with a harvest volume of 0.5L. If using the shaking method the starter volume would be 4.3L with a harvest volume of 1.2L.

This means I can keep the harvested yeast in a small bottle in the fridge, which is good because I find that fridge space taken up by brewing stuff has a direct correlation with the amount of moaning I have to listen to from the wife.
 

IainM

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Just ordered the kit. Came to £10.60 including p&p and a 25mm magnetic stirrer.
 

strange-steve

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cheapbrew

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Thanks Steve, you are a star, I wasn't sure on how many wires for the fan, or what amps for power supply and controller and size of magnets and stir bar, but Now Ordered �£7-55 :thumb:

I probably have a 12v power supply and PC fan in my junk box that would do, but as its only a few quid for the new ones I cannot be arsed looking through junk boxes.
 
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brumbrew

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Thanks Steve, you are a star, I wasn't sure on how many wires for the fan, or what amps for power supply and controller and size of magnets and stir bar, but Now Ordered �£7-55 :thumb:

I probably have a 12v power supply and PC fan in my junk box that would do, but as its only a few quid for the new ones I cannot be arsed looking through junk boxes.
Mines made entirely out of junk. The speed controller of mine is just a volume knob from an old stereo that was on the street.

The usb lead is one that was already broken, at the phone end. So good for me ;-) I just pop it into a phone usb charger when I use it.

The fan was actually the only purchase. But from a local pc store and it was only a quid as it was 'scrap' to them anyway.

I suggest everyone do it. I've harvested some good yeasts that just need 24 hours back on the plate before they're ready to go.
 

strange-steve

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Mines made entirely out of junk. The speed controller of mine is just a volume knob from an old stereo that was on the street.

The usb lead is one that was already broken, at the phone end. So good for me ;-) I just pop it into a phone usb charger when I use it.

The fan was actually the only purchase. But from a local pc store and it was only a quid as it was 'scrap' to them anyway.

I suggest everyone do it. I've harvested some good yeasts that just need 24 hours back on the plate before they're ready to go.
I like your style, clever use of the usb cable too :thumb:
 

Pirate_Pete

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Mines made entirely out of junk. The speed controller of mine is just a volume knob from an old stereo that was on the street.

The usb lead is one that was already broken, at the phone end. So good for me ;-) I just pop it into a phone usb charger when I use it.

The fan was actually the only purchase. But from a local pc store and it was only a quid as it was 'scrap' to them anyway.

I suggest everyone do it. I've harvested some good yeasts that just need 24 hours back on the plate before they're ready to go.
This is pretty much the same as the bits I've collected except I didn't pay for the fan either.

I was driving past a house one Sunday morning and there was a computer there. 5 minutes later on the way back I stopped to pick it up. Then the lady who was putting the junk out walked down the driveway. I told her I wanted the fans and the magnets out of the hard drive. She was quite happy it was going to some use. Speed control I have is out of some old computer speakers.
 

Martybhoy

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Good guide. I'm definitely considering doing this to increase my yield.

What size of stirrer did you use?
 

Martybhoy

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Ah...just saw the links to the parts.

Good work and thanks for the links.
 

IainM

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I've got all the parts except the stirrer now. Hopefully I can get it ready in time to build up some Wyeast American Ale II for my upcoming Black IPA.
 
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