# Stir Plate Problem



## dwoody1014 (18/8/15)

Hi all,

I've been trying to build a stir plate but having a lot of trouble. Followed many posts but still no luck.
My fan is 12v and 2.5A
My power supply is 9v DC and 1.5A

When connecting power directly to the fan it keeps getting faster then eventually cuts out.
I tried adding a potentiometer (500ohm then 5000ohm) but the fan would only turn on at the top of the turn and at full speed.
Tried adding an LM317T regulator but blew both pots up! Maybe a wiring issues?

Finally I followed this post http://www.topofthehillbrew.com/stir-plate/ and I think I'm close. The fan turns on, albeit quite slowly, but then stops almost straight away.

Is there anyone out there with more electronics knowledge than me (which is near zero) that can help? Have spent almost a week on this and may just go buy a stir plate soon :unsure:

Thanks heaps!
Dan


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## Tropico (18/8/15)

Try a 12v 3amp power supply


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## Ducatiboy stu (18/8/15)

dwoody1014 said:


> My fan is 12v and 2.5A
> My power supply is 9v DC and 1.5A


There is your problem.


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## dwoody1014 (18/8/15)

Ok thanks. I tried a 12v 1A but it didn't spin at all. So it's the amps that's the key? Sorry, told you I knew nothing about electronics!


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## Tropico (18/8/15)

Volts and amps have an interesting relationship when it comes to motors. The more load on the motor the higher the current draw without voltage drop, until it all turns bad and the power supply cannot supply sufficient current.


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## Ducatiboy stu (18/8/15)

And then some bloke invent Alternating current and things got really interesting


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## gunn (18/8/15)

what kinda fan are you using that is 2.5A? all you need is a simple pc cooling fan drawing 100-200mA


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## dwoody1014 (18/8/15)

It's a pc fan from an old Dell tower. Might try and find another one from work


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## TheWiggman (18/8/15)

2.5A 12V is a serious fan for a stir plate. My PC CPU fan is 0.2A and it can go pretty hard. 
For a DC system, the voltage and fan speed are related (excluding PWM and similar fancy stuff). The current will increase as the load/demand increases. Plugging a 9V 1.5A supply should immediately spin the fan slower than its rated speed. The fact you've put a 12V supply on it and it doesn't spin at all makes me think there is something wrong with the fan.


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## gunn (18/8/15)

I built mine using this http://www.ebay.com.au/itm/Computer-PC-CPU-3-Pin-Cooling-Fan-Speed-Controller-WS-/321743555938?hash=item4ae9690d62
and this http://www.ebay.com.au/itm/Black-12V-80mm-PC-Computer-CPU-Cooling-Fan-Case-3Pin-Cooler-/281311671639?hash=item417f7b7557
just add a box and dc jack.

ive used mine with a 9V DC supply and is fine.


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## Tropico (18/8/15)

If it is an old plug-pack power supply that you are using, it is more than likely a bit dicky too. Nothing but trouble those old plug packs.


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## dwoody1014 (18/8/15)

Thanks for everyone's help. Think I'll grab a cheap fan from msy tomorrow.


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## dwoody1014 (19/8/15)

Just wired up a $1 (yep, one dollar!) 80mm fan I got from MSY. No idea of the volts or amps but it works fine, although the pot doesn't seem to change to speed at all. Not too concerned at this stage cause the stir bar sticks and the vortex is ok I think. Perhaps the pot is too big at 5000ohms?

Anyway no time to sort it out now, need to do a starter tomorrow ready for my first IPA.

Thanks again!


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## marksy (23/8/15)

How have you wired it?


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## dwoody1014 (23/8/15)

Yep, wired it up and the speed is perfect for a 1L starter. The pot does not seem to change the speed of the fan but I'm not too concerned as it's doing the job at the moment.


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## SBOB (23/8/15)

Replace the pot with one of these for a better speed control option 

http://m.ebay.com.au/itm/DC-12V-8A-LED-Light-Protect-Strip-Dimmer-Adjustable-Brightness-Controller-IG-/261951260704?nav=SEARCH


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## Yob (24/8/15)

Shit dude..

http://www.digitalhomebrew.com/diy-magnetic-stirplate-kit-v2


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## mofox1 (24/8/15)

Yob said:


> Shit dude..
> 
> http://www.digitalhomebrew.com/diy-magnetic-stirplate-kit-v2


With the amount of faffing about with different fans, broken fans, magnet spacing and super gluing my fingers together... This would have been a much better option.

Just add enclosure.


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## dwoody1014 (24/8/15)

mofox1 said:


> With the amount of faffing about with different fans, broken fans, magnet spacing and super gluing my fingers together... This would have been a much better option.
> 
> Just add enclosure.


Agreed. Wish I new about this 2 weeks ago!


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