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Disaster, Thy Name is Stirplate

Posted by homebrewdad on 1/06/2015 at 11:29:46 AM

A few nights ago, I thought I'd put together a starter of ECY-29 (Conan) yeast. I figured that I'd grow enough for my IPA, my 2 gallons of cider, and some to save for future batches (via the Brulosophy yeast harvesting method). All told, I'd be making a ~3.5 liter starter.

Hah. Hah hah. Hah hah hah.

I had foolishly asked my 16 year old son to take my DIY stirplate down to the basement at Christmas time. Shockingly, he wasn't overly careful with it, and placed it somewhere that it ended up falling a couple of feet to the ground (where I found it lying on its side).

After twenty something tries to get the starter going (which usually takes one, maybe two tries to do) - all resulting in a thrown bar - I put the flask on the ground, grabbed a spare stirbar, and placed it directly on the powered down plate. BAM, the bar instantly relocated several inches off center.

So, I opened the sitrplate case, and discovered that yes, the magnet was detached from the fan. Crap.

First off, I tried gluing the washer/magnet combo back onto the fan with Gorilla super glue... no dice, it simply would not stick. I spent a good half hour digging around the basement in search of a hot glue gun, found one, applied the combo using it. This worked for all of about five seconds before throwing the magnet again.

Next, I reverted back to the super glue - this time, with an extended clamp. It stayed put, all was right with the world. I went to bed.

The next morning (New Year's Eve), I awoke to the sound of... nothing. The stirplate was not spinning whatsoever. The LED on my power switch was off. I could very faintly detect the smell of burned electronics. Rats.

My build used a rocker switch with an LED, which flowed into a potentiometer, which then allowed me to regulate the power of the fan. I had been dubious about that rocker switch from day one (what with the made in China quality and low price), so I decided to eliminate that as a possibility. I pulled up wiring diagrams on the internet and learned anew that I don't understand electricity quite as well as I thought I did. However, I eventually got things rewired so as to skip the rocker. Plugged it all up...


So, I checked the wiring again. Nothing. Changed some things. Nothing. I smelled the fan closely, and could definitely detect that burned scent. Crap, was the fan bad? Now what?

I started moping, figuring that all was lost. Sure, I'd grow some yeast in a shaken starter, but nowhere near enough to cover all of my needs. My wife asked me if I didn't just have another fan, which I did not, so she took it upon herself to start checking around for me. Best Buy had a 120mm fan listed in stock for $11, so she sent me on the way. I loaded up my three year old son, and we took a road trip to pick up a fan (plus food to grill during the coming weekend).

I picked up two fans, but our errands took longer than expected; by the time we got home, we had just enough time to eat before loading everyone up for the annual trip to my mother's house (she does fireworks on New Year's Eve).

Came home, got everyone settled in, then got to work. Okay, let's go ahead and cue my theme song.

This fan had three wires - hot, neutral, and tach... but they were of course not labeled. I *thought* I knew which was which, and yet...

  • No combination of wiring would work with the rocker switch in use.
  • No combination of wiring would work with the rocker switch bypassed.
  • Tried connecting the fan directly to the 12v supply (with only a brief touch - past experience has taught me that a direct 12v will absolutely burn up a CPU fan). Nothing.
Could the power supply also be bad? Perhaps I had experienced some surge overnight that had burned out the power supply, the switch, AND the fan?

Down to the basement I went in search of an unused plug. I found a likely candidate - a 9v plug that went to some unknown device. I hacked the end off, stripped the wires, and repeated the above steps.

  • No combination of wiring would work with the rocker switch in use.
  • No combination of wiring would work with the rocker switch bypassed.
  • Tried connecting the fan directly to the 9v supply. Eureka! The LEDs on the fan lit up and it started to spin!
Back to the drawing board I went. Rechecked my wiring for the umpteenth time. Cursed my wiring connectors more times than I care to admit. Finally, though, I had success - the rocker switch seemed truly dead, but I did get the fan to come on with the potentiometer. Man, it seemed faster than before, though...

Once again, the washer/magnet combo did not want to glue on properly. With a few tries (and some help from magnetism), I eventually got it to work. Put the whole thing back together, put the flask on top, plugged it in - which immediately gave me the best vortex I'd ever seen on this stirplate.

Honestly, I knew that there was no way it could keep going at this speed. The bar would be thrown any moment now. I turned the potentiometer as low as it would go, but still the stirplate spun at breakneck speed, clattering all the while. Perhaps the potentiometer was also damaged?

There was nothing else to do at this point but clean up and go to bed. I had no spare potentiometer, and there would be no store open before January 2nd that might carry one. I had now logged a solid five hours troubleshooting and working on this stupid thing, not to mention the time in driving and such. Disaster, thy name is stirplate.

Only, New Year's Day greeted me with a loudly clattering stirplate, a fluffy krausen, and an absolute STORM of yeast particles swirling around the flask. Before long, the vortex was invisible, hidden beneath a giant bubble. All through the day and all the following night the silly thing ran without a hitch until I unplugged it the next morning to cold crash my starter. Judging by the amount of yeast solids I ended up with, my starter did not suffer from the 24 hour period prior to me plugging it up.

I miss the LED on/off switch, but I can't deny that the silly stirplate works better than it ever has before. So... yay for damaging surges?


Tags for this post: stirplate, diy, yeast, starter, troubleshooting

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Nice fix in a pinch, but you're "going to let the smoke out" of your electrical components again with that setup, sooner or later.

Here is [a build for more robust setup that would pass Underwriters Laboratories certification](, i.e. it is unlikely to burn your house down.

posted by Chino Brews on 1/06/2015 at 12:26:32 PM

Thanks for the link, Chino.

posted by homebrewadad on 1/10/2015 at 10:11:18 PM

A good read. I think most home brewers have been there. I know my stir plate has cost me countless hours at home and work (I am in the HVAC industry where we have some slow periods, working for my FIL has perks).

I am not electrically inclined, so it definitely took me a while to get the enclosure built and then the fan wired. Then balancing the magnets and ensuring that the stir bar will not get thrown. I feel for you man. But good job on getting it working.

posted by th3beerman on 1/26/2015 at 03:32:54 PM

Heh, thanks. It was a silly process.

posted by homebrewdad on 1/26/2015 at 03:36:45 PM