Tight Arse Stir Plate

[sanmerah]

Happy to help, glad it worked out so well for you.

Must admit i'm a bit stunned you've got it working off a 3.7V supply. The LM317 has a 2V minimum dropout, which means less than 2V that's going to your load. a 12V fan shouldn't spin up at all with that supply, especially with such a heavy load.

I didn't think it would work either ... but it did!

 

[A3k]

I didn't think it would work either ... but it did!

Hi Adelaide Brewer,
Where abouts did you get the stir bar from.
I'm in adelaide and want to get one. I have everthing else, but am just missing that. (and maybe a bigger flask)

Cheers
Al

 

[orac]

Hi Adelaide Brewer,
Where abouts did you get the stir bar from.
I'm in adelaide and want to get one. I have everthing else, but am just missing that. (and maybe a bigger flask)

Cheers
Al

I recently bought a couple of stir bars & flask from:

Asis Scientific 474 Port Rd, Hindmarsh 5007


They seemed quite happy to sell small quatities and were helpful when I phoned them...tried a couple of other scientific supply places from the phone book and they were only interested if I was buying a hundred or so.


Dave (1st post btw)

 

[HoppingMad]

Got inspired and now working on building one of these. The wiring might be interesting though, not much of a sparky myself.

Found some rare earth magnets in an old hard drive (pic below).
Found info about them here - EarthMagnets in stuff Now gotta prise them out somehow.

Hopper.

 

[altone]

Got inspired and now working on building one of these. The wiring might be interesting though, not much of a sparky myself.

Found some rare earth magnets in an old hard drive (pic below).
Found info about them here - EarthMagnets in stuff Now gotta prise them out somehow.

Hopper.

Think that this has been covered already somewhere in the thread, but the way I've done it in the past is to get 2 sets of strong grips or pliers, one each end of the steel backplate and just bend it away from the magnets - try not to prize the magnets themselves as they can be brittle.

Trust me I'm a computer technician :icon_cheers:

 

[gava]

has anyone used a stirer for their fermenter?
what advantages would this bring? would the benifits outway the trouble of setting it up?

Well not unless I use one of these:

 

[jonocarroll]

Sorry to have multiple questions on the go fellas, but I'm working on my TASP and I'm curious; is there a particular reason for sealing the fan up in a box? Seems a lot of people are concerned about heat extraction from their sealed box... why not just have a table arrangement with the wiring appropriately sealed up?

I'll hopefully be putting mine together over the weekend, and will post build pics for assessment. I'm hoping that the 10cm, 3-speed computer fan I got for nix will be strong/weak enough that I don't need to regulate the power.

Cheers to all contributors of this uber-thread.

 

[Supra-Jim]

No need at all QB. Having the unit build in a PVC box just makes it nice and asthetically appealing

We recently had some different constructions demo'd a Melb Brewers meeting and the majority of the design variations did not have a sealed unit. One design was a peice of cork board with legs make from cork and the fan attached to the underside with PCB plastic stickon stand offs. Other designs used a plate sitting over a bowl.

I guess the main idea is to have a surface to support the flask, and a way of attaching the fan underneath, everything else is window dressing.

Cheers SJ

(edit: I built mine in a PVC enclosure so it looks cool! )

 

[gava]

I put mine in a jiffy box because it's portable and water resistant.... Im sure it wouldn't matter as long as it spins the stirbar...

 

[jonocarroll]

Cool, cheers for that!

I'll likely go some sort of table setup - either varnished wood or plastic, I'll see what I can get my hands on.

:icon_cheers:

 

[captaincleanoff]

I made a tight *** plate that worked well, but have recently required a proper stir plate from work. Its a big stainless square thing.. will find out the model later if necessary

I'm stiring 5L starters no problem with this.

My problem though, is that the stir plate heats up quiet alot. I keep my starters and stir plate inside my fermentation fridge, at the appropriate temperature (usually 17c). However, when I recently checked a starter that had been stiring for about 24hrs, it was up around 30c I touched the top of the stir plate, and it had gotten fairly hot.

Anyone got any ideas how to prevent this? One idea I had was to connect the stir plate to a timer, so it turns off for a period every hour or so to cool down.

Or maybe a layer of foam between the stir plate and flask?

Just wondering if others have problems with this, and how they fixed it.

 

[Supra-Jim]

Thin layer of foam or neoprene could do the job there, or otherwise as you mentioned, use a timer switch and set it to switch the unit off every odd hour.

Cheers SJ

 

[jonocarroll]

Anyone got any ideas how to prevent this? One idea I had was to connect the stir plate to a timer, so it turns off for a period every hour or so to cool down.

Or maybe a layer of foam between the stir plate and flask?

Anything you do like this will only (in the first case) prevent a lot of heat from building up, or (in the second case) heat up the foam, either melting it or bringing it up to the same heat as the plate, in which case it's no better.

You need to actually get the heat out - either by running the fridge, or by using BribieG's method of putting ice bricks in the fridge with the starter. Otherwise you're just moving the heat around inside the fridge.

 

[newguy]

I made a tight *** plate that worked well, but have recently required a proper stir plate from work. Its a big stainless square thing.. will find out the model later if necessary

I'm stiring 5L starters no problem with this.

My problem though, is that the stir plate heats up quiet alot. I keep my starters and stir plate inside my fermentation fridge, at the appropriate temperature (usually 17c). However, when I recently checked a starter that had been stiring for about 24hrs, it was up around 30c I touched the top of the stir plate, and it had gotten fairly hot.

Anyone got any ideas how to prevent this? One idea I had was to connect the stir plate to a timer, so it turns off for a period every hour or so to cool down.

Or maybe a layer of foam between the stir plate and flask?

Just wondering if others have problems with this, and how they fixed it.

If you switch back to a homemade stirrer with a plastic top you won't have a heating issue. You mentioned that the commercial unit you snagged has a metal top - it's responsible for the heating. Wave a magnet around a conductor (the metal top), and the magnet induces an electrical current in the metal. Electrical current flowing through metal creates heat. Eliminate the metal and you'll eliminate (or greatly reduce) the heat.

 

[LethalCorpse]

Heat is always going to be a problem with speed control, particularly if you're not using a PWM controller - linear controllers, like the simple circuit I've recommended, produce heat by their very nature. Sealed boxes are a good idea because they stop spillage (which happens more often than any of us would like) from buggering up your electrics. But sealed boxes trap the heat in. Perhaps the best option is to use the lid of a jiffy box, or some other flat panel, with the fan attached to it with spacers so there's a small airgap between the fan and the panel. The PCB/veroboard with all components soldered to it goes directly underneath the fan. Use a heatsink on the LM317 so that the airflow produced by the fan can cool it happily. You'll need to use a TO220 heatsink mounting kit. This consists of a rubber gasket and a plastic ferrule which ensures that the heatsink has a solid thermal interface with the LM317, but no electrical connection because the tab of the LM317 is connected to its output, and you don't want the heatsink to be live. You can buy it at Jaycar or wherever else you buy the other bits for a dollar or two for four sets. Appropriate selection of screws and standoffs will ensure you've got a nice flat surface for your flask to sit on, and the fan and pcb are at about the right heights. The attached diagram should explain it far better than I can here. If you use a panel which is a fair bit larger than your fan, PCB and flask, it should stop any spills from hitting the electrics, particularly if you use something with a lip.


Captaincleanoff, are you certain the commercial stirplate you're using isn't a heater/stirplate? They're fairly common, as you often wish to heat the liquid you're stirring in assorted scientific fields. If it's just the unit producing heat, and you've got it in a fridge, a small fan pointed at the unit should ensure it stays close to the same temp as the fridge. Also, what newguy says is 100% true, and could well be causing the heat you're getting. Hopefully the metal top can be easily removed if that's the case. If not, the fan should help either way.

 

[3G]

Hi Adelaide Brewer,
Where abouts did you get the stir bar from.
I'm in adelaide and want to get one. I have everthing else, but am just missing that. (and maybe a bigger flask)

Cheers
Al

Hi Al

I got mine from Aim Scientific in Prospect a few years back. The guy there is helpful.

Cheers

 

[altone]

Thin layer of foam or neoprene could do the job there, or otherwise as you mentioned, use a timer switch and set it to switch the unit off every odd hour.

Cheers SJ

That's what I'm doing - actually a mousemat cut to fit, makes the thing run quieter as a bonus.

 

[jonocarroll]

I got mine from Aim Scientific in Prospect a few years back. The guy there is helpful.

Just called him. I might try to get mine tomorrow. Will have to (try to) avoid also buying lots of funky lab equipment h34r:

Cheers all!

 

[Maple]

I think I'm in need of a bit of help with this one. I've been collecting all the bits and bobs for building one of these lil beauties, and finally had the time to sit down and try to work out how it all goes together. Well, managed to get it all wired up, fan comes on with the switch, speed modified by the knob (yeah, one turning the other), but when I put a flask with a stir bar on and fire it, the stirrer begins to spin, I get all excited, and then it just starts flicking around the flask bumping all random-like until i turn it off. Tried turning the fan speed down to just before it cuts out, no change.

The magnets are the small rare earth magnets from Jaycar, the stir bar is a 35 x 6mm cylindrical one. I've tried moving the magnets inward on the fan, outward, stacking them 2 high on opposite sides of the fan as well. pretty sure I have one N facing up and the other S facing up.

I guess the questions are: are the magnets too strong/not stong enough? or is the fan still to fast (hard one to answer without seeing it i guess), is the distance between the flask and the magnets too big/small? (currently ~ 20mm gap, but tried smaller, no change), any advise would be welcomed.
Cheers.
Maple

 

[jonocarroll]

I might try to get mine tomorrow. Will have to (try to) avoid also buying lots of funky lab equipment h34r:

Stirbar(s): WIN
Restraint in buying more equipment: FAIL.

Table setup built. Fan connected/tested. Magnets should arrive soon.