How to build a stir plate for less than ten quid

[foxbat]

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.

 

[blawford]

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.

 

[nigelnorris]

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.

 

[AlanManley]

Right parts ordered, instructions read and saved...

Roll on the delivery day!

 

[Dutto]

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.

 

[nigelnorris]

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

 

[AlanManley]

This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

Sent from my SM-G950F using Tapatalk

 

[Gerryjo]

This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

Sent from my SM-G950F using Tapatalk

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.....

Gerry

 

[strange-steve]

This may be a really REALLY stupid question... do I need a soldering iron?

Or will I get by with electrical tape?

Sent from my SM-G950F using Tapatalk

The power supply and fan both connect to the PWM which has screw terminals so you don't need to solder.

 

[AlanManley]

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".

Sent from my SM-G950F using Tapatalk

 

[nigelnorris]

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.

Gave up on that idea, getting the right bits was either too expensive or involved waiting months for them to come from China and still costing 5x as much as a vanilla version. Here's my casing, plant pot saucer:

Thanks for a great idea Steve!

 

[Dutto]

That looks the dog's doodads! :thumb:

The ingenuity of the people on this Forum never fails to amaze me. :lol:

 

[private4587]

Hi Steve. Have looked at Erlenmeyer 5l flasks and they are extremely expensive so wondering what i need to make a more powerful version to use with my demijohns. I presume a bigger fan and extra magnets?

Hi BeerCat did you ever get the stir plate to work with your demijohns? would like to know before i make the plunge to make one has do not want to go down the route of Erlenmeyer flask.

 

[BeerCat]

Hi BeerCat did you ever get the stir plate to work with your demijohns? would like to know before i make the plunge to make one has do not want to go down the route of Erlenmeyer flask.

No i didn't and am going to go down the flask route. I tried a larger 120mm fan but was too slow and flimsy. The 80mm wouldnt move the bar even with 3 magnets so going to go for a 100mm fan.

 

[Fil]

you can epoxy a scrap dvd/cd or similar disc to the hub of a standard pc fan to provide a wider platform upon which to mount your drive magnets

 

[private4587]

OK it looks as if a demijohn on stir plate is a no go, does anyone know of suitable vessel that can be used without going down the expensive route of elmeyer flask? I want to be able unto a 2lt starter.

 

[Junglist69]

Try this place for cheap flasks, under a tenner for a 2000ml. Postage ain't too bad either

https://www.creamsupplies.co.uk/academy-glass-conical-flask-2000ml-huge

 

[nigelnorris]

OK it looks as if a demijohn on stir plate is a no go, does anyone know of suitable vessel that can be used without going down the expensive route of elmeyer flask? I want to be able unto a 2lt starter.

If you need a big container then one of the 5L plastic water bottles you can buy for a quid would work. Even if the base is concave like a demijohn you could raise the magnets into the recess.

 

[stigman]

I've used a dj on my stirplate, it's a bit tricky to get it to grab and pull it to the Centre but I managed. I have an erlenmeyer now though much easier and you can boil on it as well.

 

[peebee]

Hi BeerCat did you ever get the stir plate to work with your demijohns? would like to know before i make the plunge to make one has do not want to go down the route of Erlenmeyer flask.

I started a thread on the similar subject (45-65L batches, 2L Euleymer flasks just not big enough). I'd given up with the idea of a demijohn and wondered if you could split a starter across two flasks/stirrers.

No suggestion you can't so it is the route I'll be taking (will swallow hard and close my eyes before ordering TWO 2L Euleymer flasks; and I've another stir plate to build now).