Diy Computer-fan Stir-plate Build

[Dazza88]

Malted, i wouldn't know either but what about a pc fan controller?

 

[Malted]

Malted, i wouldn't know either but what about a pc fan controller?

As far as I can tell they are not PWM's, they just dial down the voltage. Lower voltage = lower grunt?
A PWM keeps it at 12 volts but switches on and off very rapidly (like 30 times a second) to regulate the speed. Thus when it is on it's got the 12volt grunt.

 

[Wolfy]

Malted, make sure you read through the Tight Arse Stir Plate thread - if you have not already - there are many different comments/suggestions/options there. All I was really trying to do here is to make the process of building a workable stir-plate as cheap and easy as possible for anyone who can connect a couple of wires together.

Personally - if you plan to continue using a computer-fan based stir-plate - I think you are over-analyzing things, these things are designed to spin under virtually no load and push air, so worrying about PWM, torque and all that is simply over-kill. For stirring larger volumes, increase the stir-bar size or increase the fan speed, and I think you'd do as much or more as using a PWM solution (if you were sill using a computer fan).

Stirring the starter is mostly about 3 things: introducing oxygen, degassing CO2 and keeping the yeast in suspension, so even if the stir-plate does not have a noticeable vortex at larger volumes - but is still mixing the starter well, it should still be doing all those things.

 

[Malted]

Malted, make sure you read through the Tight Arse Stir Plate thread - if you have not already - there are many different comments/suggestions/options there.
All I was really trying to do here is to make the process of building a workable stir-plate as cheap and easy as possible for anyone who can connect a couple of wires together. Yes you certainly have achieved that, sorry for sullying it.

Personally - if you plan to continue using a computer-fan based stir-plate - I think you are over-analyzing things, these things are designed to spin under virtually no load and push air, so worrying about PWM, torque and all that is simply over-kill. For stirring larger volumes, increase the stir-bar size or increase the fan speed, and I think you'd do as much or more as using a PWM solution (if you were sill using a computer fan). This answers my questions.

Stirring the starter is mostly about 3 things: introducing oxygen, degassing CO2 and keeping the yeast in suspension, so even if the stir-plate does not have a noticeable vortex at larger volumes - but is still mixing the starter well, it should still be doing all those things.

G'day Wolfy, sorry mate, I wasn't knocking you. I was just trying to clear my head. Thank you for the answers.
I am genuinely happy to retract (delete) my post from here if you like (to clean it up). Let me know.

 

[felten]

Felten, you got details on your housing?

It's a big Tupperware container

Those LED dimmers linked a few posts up are PWM controllers, at least it says "PWM digital dimming" on the pamphlet that came with it.

 

[Wolfy]

G'day Wolfy, sorry mate, I wasn't knocking you. I was just trying to clear my head. Thank you for the answers.
I am genuinely happy to retract (delete) my post from here if you like (to clean it up). Let me know.

No offense was taken, and I've no idea if my theory is correct or not - it may well be that I'm not right - but was just posting my (uneducated) thoughts on the subject.

 

[a1149913]

Hi, just wondering what the specs of your power supply are. I'm making a stir plate and i'm using an old nokia phone charger but it doesnt seem to power the fan enough. It doesnt ever reach maximum speed (even without the stir bar) and will most of the time struggle to get going.

Thanks, Jacob

 

[Wolfy]

Computer fans are rated at 12V (but they usually operate from 6-15V, just at different speeds depending on the voltage).
Last time I looked at a Nokia charger it was less than 12V.

 

[ben_harvey]

From memory I think that Nokia (or other phone chargers) are around 5V, give or take.
They probably have pitiful output current as well.

Keep in mind that at low voltage you need more current to supply the same power (power = volts x amps) so a 6 watt (just picking a number out of my head) fan would draw half an amp if it was designed to run at 12 volts but it would draw 1 amp if it was designed to run at 6 volts. The designed-for-12 V fan would have a resistance of 24 ohms and the designed-for-6 V fan, 6 ohms.

These figures don't apply if you're running a fan designed for 12 V at 6 V, as the current drops proportionally to the voltage, however I think that power drops with the square of the voltage applied (i.e. half voltage = 1/4 power). This would explain why the phone charger has issues running the fan, it's supplying half the voltage but really it only supplies a quarter of the power. Theoretically the fan should run at a quarter speed but it can't overcome friction to get started.

Clear as mud?

I'm not a sparky or anything, but I guarantee* this information is correct at the time of writing.


*not a guarantee

 

[Amber Fluid]

The mobile phone charger I have runs at 3.5v and has no problem starting up and maintaining an adequate speed to push air around. I say the proof is in the pudding and therefore, I don't know about your theory, but it certainly does not apply in my case.

After a bit of research on this forum as well, I can't recall anyone else having issues with their fans starting up either. However, I really shouldn't be speaking for other people, just stating what I have read here.

 

[Wolfy]

Clear as mud?

Yep, clear as mud.

The fans I used in the OP are 12V 0.3Amp so you can put that into whatever formula you like, but in general they work fine at a wide range of voltages.

 

[ben_harvey]

Ok fair enough then. I was under the impression the low voltage charges were a bit useless. I'm not speaking from experience here as I haven't built one of these things yet, but I plan to as soon as I get back from site.
I just found out a guy from work brews beer and he highly recommends liquid yeast (he still uses kits though! He gets his cultures from a microbiologist in Perth) so I can't wait to give it a shot.
It's just so expensive, hence 'll try and make a few cultures and see how I go.

Thanks again for the post Wolfy.

 

[tones0606]

Just waiting on magnets and stir plate.
Will post some pics hopefully in the next few days.
So simple to build.
Cheers

 

[bear09]

Hi All,

Just wanted to add some pix of my attempt at this stir plate. Note that I used the original container from a stir plate that I previously purchased from the US (http://www.aussiehomebrewer.com/forum/index.php?showtopic=53670). The variable resistor on the one from the US stopped working - it was either on or off - no in between. Also, I was never happy with its top speed - it could never vortex all the way to the bar like some you tube examples I had found.

Anyhow I followed the instructions on this post and after 2 hours of adjusting the height clearance (no kidding thats how long it took me to get it to balance) this was the result...

Im really happy with it. Spins bloody fast and the variable resistor has an awesome range from no to full on go.

Give it a go yourself. CHEERS for the help!!

 

[Charst]

looks good, I'm planning on getting mine finished this weekend, turns pretty well just finishing the top, can anyone give me any advice on getting it to spin quieter? sounds like a marble rattling around in there.

 

[Acasta]

Not that this tutorial isn't easy enough to follow! But heres a video I found doing this project. Looks so easy. http://youtu.be/XVLB9c0j1iU

 

[felten]

I was waiting for him to cut himself :X

I managed to bury most of my pocket knifes small blade into my thumb while making mine.

 

[beerdrinkingbob]

not sure why he didn't use the pliers to strip the wires, the blade looks a bit dangerous.

Thanks for the link acasta, brings it all together

 

[bear09]

looks good, I'm planning on getting mine finished this weekend, turns pretty well just finishing the top, can anyone give me any advice on getting it to spin quieter? sounds like a marble rattling around in there.

Adjust the height clearance.... Like I said above, I literally spent 2 hours doing this. I didnt think there would be much in this but .5 of a mm made a difference. Also making sure the fan was level helped too. I finall found the sweet spot where the fan has maximum rpm and the bar makes a little noise only every 30 sec or so.

 

[davo4772]

Stir bars on fleabay.

Ordered a 27mm for A$5.75. Free postage


Here

No great loss if it turns out to be rubbish.