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The HomeBrew Forum > Beer Brewing Talk > Beer Brewing "How-To" Guides > How to build a stir plate for less than ten quid

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Old 23-06-2017, 02:31 PM   #221
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Ok, understood. So you're saying then that if connecting a 2 wire fan to a PWM it's really a flip of a coin whether it'll work or not?
Pretty much. If you're stuck with a controller that outputs a PWM wave that's not working for you and you've got a few cheap components handy you can build an RC low pass filter on the output that will 'convert' the square wave to an analog level. There are web tutorials around on how to do that.

If it were me I'd just use a Zalman Fanmate 2 - it'll work on all fan types and I think the '2' revision is now using a more efficient buck converter instead of a rheostat. The only drawback is that it can't go down as low as the fan will physically go.
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Old 24-06-2017, 09:46 AM   #222
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Done!

Was a maybe a happy co-incidence that the fan didn't work, I took one out of an aging PC that ended up being an exact fit to the enclosure I was planning on using (Chromecast Audio box) which meant I didn't need to fix it in place and made fine tuning the height easy.


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Old 25-06-2017, 12:05 PM   #223
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Fancy having a go at this, plus I have a bunch of rechargeable batteries I'm not using so might try to make a rechargeable version.
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Old 27-06-2017, 07:44 PM   #224
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Right parts ordered, instructions read and saved...

Roll on the delivery day!
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Old 28-06-2017, 10:15 AM   #225
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Fancy having a go at this, plus I have a bunch of rechargeable batteries I'm not using so might try to make a rechargeable version.
Before actually making the machine I suggest that you test the system to make sure that the batteries are up to the job.

Remember that for some yeast starters you may want the stir-plate to run continuously for 48 hours.

I use a couple of deep-cycle 12V batteries from my Mum's old scooter and although they still hold the charge okay the speed of the spin-plate falls off significantly after 48 hours if I only use a single battery.
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Old 28-06-2017, 03:57 PM   #226
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Before actually making the machine I suggest that you test the system to make sure that the batteries are up to the job.

Remember that for some yeast starters you may want the stir-plate to run continuously for 48 hours.

I use a couple of deep-cycle 12V batteries from my Mum's old scooter and although they still hold the charge okay the speed of the spin-plate falls off significantly after 48 hours if I only use a single battery.
Here's what I'm thinking. [35 years since I failed my A level Electronics exam so please anyone who knows better feel free to shout up before I start cutting holes in boxes].

Instead of AA batteries it's occured to me that I can use [that's also spare lying dusty in a box somewhere] an old usb power bank like this, mine is 24000 mAh, AKA 24Ah.

Typical [usb] case fan @ 0.5 watt will be drawing 0.5w/5v = 0.1 amps. So that's using 0.1 x 24 = 2.4 Ah per day. With everything running to spec that would give me ten days continuous use. Even an old battery and a cheap fan using more current than specified should still be good for two days. Even one day, or a day then an hour's charge then a second day is going to be pretty useful.

Did I do the maths right? I hope so because I can just use one of a zillion phone chargers than are lying around in the house and only buy a usb case fan, a switch, and a 5v pwm controller to build it. Got a big bag of usb cables somewhere to chop up for the wiring. Still well within the tenner quoted in the OP
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Old 28-06-2017, 05:11 PM   #227
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This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

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Old 28-06-2017, 08:25 PM   #228
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This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

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Electrical tape is purely for Identification only.Why not try an electrical connector i.e. 5 amp connectors,molecular or bullet connectors to make a good solid connection and most importantly keep it safe.....

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Old 28-06-2017, 08:28 PM   #229
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This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

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The power supply and fan both connect to the PWM which has screw terminals so you don't need to solder.
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Old 28-06-2017, 08:37 PM   #230
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The power supply and fan both connect to the PWM which has screw terminals so you don't need to solder.
Win!

Cheers. I am no it mechanically or electrically at all so glad it's going to be a bit "simple".

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