For crying out loud-why wont my damn stirplate work right

[Crut]

OK so my buddy finally got me the rheostat he said he had for me. The one we had before would either be full blast or totally off. Well this one isnt much better. IT came with his computer to control the extra fan, but wont control my stirplate fan enough. Im using a 5.9V phone charger for power, but it seems i cant get it down to a reasonable speed. In a 1000 ml flask, it makes a 2-3 inch vortex and seems to be cooking right along. I dont wanna kill my yeasties by splattering them on the side of the flask. You gotta help me, my yeast depend on you.

[J.Brew]

Kepp in mind that I know next to nothin about electronics but one option might be to hook a second rheostat in line before the first. You could also wire in an inline resistor, they'rs cheap and worked for me in one of my first stir plates.

[Mylo]

Mine's very similar to Cruts... 90% of the reostat is OFF. The last 10% is SO senstive that it usually takes me 10 minutes of f'ing with it to get it just right. It's a real pain in the ass. The harddrive magnet could be a little more powerful too. As soon as it gets flung off, I have to shut it OFF to get it "coupled" again with the stir bar. Then I start the process again.

I really wish one of our "BN Army of Engineers" (ie. not me - short bus, here), would post a schematic AND a radio shack parts list. I can build shit and follow instructions - but electronics has never been my strong suit. I also need to find one or two reasonably powerful rare earth magnets so I don't pull my hair out next time I do a starter.


Mylo

[TMB]

I’m having problems controlling my home-made stir plate speed too. I have a 5 K-ohm rheostat in-line with my fan and a 12V power supply. I pretty much go from not moving to full bore with little adjustment when a flask is on, so I think 5 K-ohm is too much and/or my fan is too small (80mm computer fan).

What I did find though is that even at full bore, a long magnet in a 2L flask and the 80mm fan will create a decent vortex because of the drag of the liquid. My other problem was the magnet getting thrown. I fixed that with cheap, but large, magnets from Home Depot instead of the small by extremely powerful magnets that I had. Bigger is better. Big and strong is even better and I found that hard drives have nice magnets (I also found this on-line later)

I’ve read through some on-line instructions for building a stir plate but most of them just say how easy it is (bullcrap) and they don’t talk about all the inputs.

If anyone has a link to a good site for building a stir plate, please post it. If not, I’ll tackle the problem in 2008.

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[Crut]

after a few hours of dickin with it, i got it so it doesn't fling them all over, it is just barely vortexing and a nice gentle stir. I have two rheostats hooked up in line with each other. It takes a steady hand to get it just right, but when its good, oh boy is it good. now just gotta solder it all up tomorrow, secure everything down, baton down the hatches and pretty it up and go to town. Time to drink, but if any of you smarties that ride the regular engineer bus can help and post a schematic, that would be greeeeeeeeeeat. I know its been somewhat explained before, but a lot of users have joined since, and may help them and myself immensely
Drink up, its celebration time for ME

[TMB]

http://www.blackstormbrewing.com/schematic.jpg
http://www.blackstormbrewing.com/magnets.jpg
http://www.blackstormbrewing.com/vortex.jpg

In the magnets picture I show a hard-drive disk and a spacer epoxied to the top of a computer fan. The spacer gives the glue someplace to go and acts as a spacer. I used big magnets because they threw the bar much less frequently. I also included a simple schematic.

On my next rev I'm going to try 120mm computer fans for a little more power.

Cheers,

[Airgead]

Guys

There are 2 types of rheostats (do you guys still call them that.. the rest of the world stopped using rheostat years ago.. but oh well) out there - ones with a linear scale and ones with a logarithmic scale. The log ones will do the sort of things you are describing - 90% of the range is pretty much 0 with the remaining 10% shooting straight up to full power. What you need is a linear rheostat. unfortunatly most of the ones out there are log as they are used as volume controls for audio gear and volume works on a log scale.

You can also get precision rheostats which take 10 full turns to go from 0 to full. That might be a good idea as it allows for very fine control.

Cheers
Dave

[Bugeater]

If anyone has a link to a good site for building a stir plate, please post it. If not, I’ll tackle the problem in 2008.

Here is once that covers the basics.

http://onebeer.net/sp_howto.shtml

Wayne
Bugeater Brewing Company