My Stirplate... Cheap and Easy Build...

[Bru]

For the guys using button magnets - how did you glue them down ?
Ive got 10mm X 3mm rare earth magnets which Ive stuck down with 5 min epoxy. Its a bit of a mission because they repell each other laterally so Ive got to hold them down untill they're stuck - I was wondering if there was an easier way. Hot glue or something quicker.

 

[Anthony_Lopez]

I would prefer epoxy over any other adhesive once I've fine tuned the magnet placement.

 

[tincob]

I just used mine for the first time last week, made two starters, I am able to get a vortex about 1/2 way down my growler for a 1 liter starter with a 2" stirbar.

I am using a 6v cell phone charger, but a buddy of mine has a bunch of old cordless phone chargers one is 9v and another is 10.5v.

I was wondering if using one of these would give my fan a little more power to pull the vortex down a bit further?

Also, if wattage is listed on the charger does that make a difference?

I think the 10.5v charger states 14 watts, and the 9v might be like 2 watts, I'm not certain, my cell phone charger that I am using now is .5 watt.

Can higher wattages burn out my fan if the charger is 12v or under?

This poster's question about the wattage was answered but I'm still unsure of his question about voltage.

I actually have a 6.5 volt and a 9 volt wall wort. All things being equal, which one will be better for the stir plate application?

I'll have to look for old PCs when I make the next dump run...

 

[Anthony_Lopez]

It all depends on the requirements of your fan.

 

[passedpawn]

This poster's question about the wattage was answered but I'm still unsure of his question about voltage.

I actually have a 6.5 volt and a 9 volt wall wort. All things being equal, which one will be better for the stir plate application?

I'll have to look for old PCs when I make the next dump run...

9 volt will spin faster. that might not be good if the magnets you are using are not strong enough to hold the stir bar. I.e., my first stir plate could only be run with about 3.3V or the fan spun too fast and the stir bar was lost.

I modified my stir plate to have 3 hard drive magnets, now I can run my fan with a full 12V, no problem.

Regarding wattage, most fans require very little power, which is measured in watts, not volts. For most fans, a 1W supply is more that adequate.

 

[tincob]

Shouldn't I be able to use the potentiometer to reduce the speed and prevent the thrown stir bar?

Anyway, I don't want to really get into a discussion about electronics. I just want to make a good whirlpool.

So, it sounds like I should look at the wattage number of both power supplies and go with something near 1 W. Not too low so I don't lose the torque but not too high otherwise the fan will spin too fast.

Thanks guys.

 

[gromitdj]

I would recommend a wall wort in the 3.3 - 5 volt range. Anything larger than that will most likely throw the stir bar even with the potentiometer set at its lowest. At least that is the experience that I had.

 

[eppo]

put mine together today, finally. works great. only problem i had was i couldnt get the fan started if i had the magnet sitting right on it. so i rigged it a bit. i glued a poland spring bottle cap to the center of the fan, glued it down, then i epoxied the magnet to the top of it. works like a charm. i got lucky enough to use (i think its an 80mm) fan from my computer that had a switch already on it for L,M,H. along with the potentiometer that i bought at radio shack. its nice because i can adjust it for 1L and 2L starters.
well, anyway, thanks for the info it was a great help.
off to my LBS to get some ultra light DME for my starter!
thanks again, and cheers!

 

[Xakk]

I used mine for the first time last night. It went from clear to snow-globe in about 8 hours. Love it.

 

[Bru]

I finished my two - one enclosure didn't have a lid so I installed it upside down in the box. I glued a 1" strip either side of the fan and used double sided velcro tape to stick it to the box. The height of the plywood and tape are working well.
The other one is conventionally mounted - facing the lid. Both work well.

In future I wouldn't bother with a switch or pot - they both worked fine connected directly to the power supply.
I loved this project :rockin:
BTW - does anyone use their stir plates inside a fridge / fermentation chamber ? I plan on installing a plug inside my ferm. chamber to run the stir plate at a set temp.
Also - can the starter get too much air from being spun too fast ?

 

[Catt22]

I finished my two - one enclosure didn't have a lid so I installed it upside down in the box. I glued a 1" strip either side of the fan and used double sided velcro tape to stick it to the box. The height of the plywood and tape are working well.
The other one is conventionally mounted - facing the lid. Both work well.

In future I wouldn't bother with a switch or pot - they both worked fine connected directly to the power supply.
I loved this project :rockin:
BTW - does anyone use their stir plates inside a fridge / fermentation chamber ? I plan on installing a plug inside my ferm. chamber to run the stir plate at a set temp.
Also - can the starter get too much air from being spun too fast ?

There really isn't a big advantage to temperature controlling a starter. Room temp is normally fine (70-80 or so). It wouldn't do any harm, but not worth the trouble IMO.

No need to be concerned about running the stir plate too fast except maybe the potential for throwing the bar. OTOH, there is also nothing to be gained by running it at high speed. It has been my experience that stirring gently works just as well as stirring fast. You really only need to keep the yeast in suspension, the wort moving and the cover loose enough to permit the gas exchange to occur. Use at least a two liter jar or flask for best results.

 

[goose_on_fire]

Thanks for the thread, guys, I learned a bunch.

Just finished mine, entirely using parts I had around the garage, except the project box I put it in. So total cost was about $6. I went with a PWM circuit using a 555 timer, an N-channel MOSFET and a handful of resistors, capacitors and diodes I had laying around. I found a 10K linear-taper pot and an illuminated switch I'd intended to use in a Volkswagen I haven't owned in ten years, and a rinky-dink 12V fan from an ancient computer.

I plug it straight into the 12V rail of a power supply I built out of an old PC power supply. It actually pulls a small whirlpool on the 5V rail thanks to the PWMing, but it's not real happy about it.

Just another time I can drag SWMBO into the garage and say, "SEE?! This is why I desolder all the parts from old VCRs and printers!" so that she can shake her head and walk away muttering... but hey, I do the same when she shows me the latest scrapbooking gadget...

Anyway, point is, I learned a ton from this and the similar threads, not only about design options but usage, too, so thanks.

 

[passedpawn]

Thanks for the thread, guys, I learned a bunch.

Just finished mine, entirely using parts I had around the garage, except the project box I put it in. So total cost was about $6. I went with a PWM circuit using a 555 timer, an N-channel MOSFET and a handful of resistors, capacitors and diodes I had laying around. I found a 10K linear-taper pot and an illuminated switch I'd intended to use in a Volkswagen I haven't owned in ten years, and a rinky-dink 12V fan from an ancient computer.

I plug it straight into the 12V rail of a power supply I built out of an old PC power supply. It actually pulls a small whirlpool on the 5V rail thanks to the PWMing, but it's not real happy about it.

Just another time I can drag SWMBO into the garage and say, "SEE?! This is why I desolder all the parts from old VCRs and printers!" so that she can shake her head and walk away muttering... but hey, I do the same when she shows me the latest scrapbooking gadget...

Anyway, point is, I learned a ton from this and the similar threads, not only about design options but usage, too, so thanks.

Don't you have a problem getting the full range of duty cycle from a 555? I recall having to choose from 0-50 or 50-100.

 

[goose_on_fire]

Don't you have a problem getting the full range of duty cycle from a 555? I recall having to choose from 0-50 or 50-100.

Nope. I don't have as scope to verify, and I know it'll never go 0% to 100%, but it shouldn't do any worse than 5% to 95%.

There's a circuit simulator at http://www.falstad.com/circuit/ that you can use to get a theoretical range... go to that URL, and in the Java applet, go to File -> Import and import the following text:

$ 1 5.0E-6 10.20027730826997 50 5.0 50
165 496 336 528 336 2 12.0
c 560 496 560 544 0 1.0E-5 7.9999999999940785
g 560 544 560 592 0
d 224 448 224 368 1 0.805904783
d 320 368 320 448 1 0.805904783
174 224 368 320 368 0 10000.0 0.5396000000000001 Resistance
w 272 352 272 192 0
w 272 192 672 192 0
w 672 192 672 400 0
w 672 400 624 400 0
w 624 368 624 304 0
w 624 304 560 304 0
w 560 272 560 304 0
w 496 464 496 432 0
w 496 432 352 432 0
w 352 432 352 448 0
w 352 448 320 448 0
w 320 448 224 448 0
c 320 448 320 528 0 1.0E-6 7.834532325997717
w 320 544 320 528 0
w 560 304 400 304 0
w 400 304 400 480 0
w 320 544 400 544 0
w 400 544 560 544 0
w 496 368 496 288 0
w 496 288 704 288 0
w 560 272 608 272 0
w 608 272 608 160 0
w 608 160 704 160 0
f 704 288 784 288 0 1.5
r 784 272 784 208 0 100.0
w 784 208 784 160 0
w 784 160 704 160 0
g 784 304 784 384 0
R 560 272 560 224 0 0 40.0 12.0 0.0 0.0 0.5
r 704 288 704 160 0 10000.0
o 29 64 0 43 20.0 1.6 0 -1

That's more-or-less the circuit I used (the 100 ohm resistor upstream of the MOSFET is the motor, I didn't feel like putting an inductor in, but you could if you wanted), you can use the "Resistance" slider on the right to move the wiper on the pot. The basic circuit I got from here: http://www.dprg.org/tutorials/2005-11a/index.html

The ~ 130 Hz frequency is a little hum-my, but it's the best I could do with the resistors and capacitors I had on had. You can change the R and C values in the circuit pretty much willy-nilly to get the frequency you want.

 

[passedpawn]

That simulator is cool. Thanks.

Careful you don't kill your FET with negative voltage spikes when the motor is turned off. Most FETs have a reverse-biased junction diode from source to drain, but not all. You need that.

 

[tincob]

Posting to give my thanks also. I used my stirplate this past week to create the starter (WLP300) for my first hefe weizen. Hope some of my comments and photos are helpful to other builders.

I tried to use stuff laying around the house as much as possible so my build came out to ~$18 all in, including the cost of stir bar and bolts & nuts.

Set up specs
- 12 volt DC microprocessor fan, the case fan was missing on the PC that I scrounged at the local dump so I gave this a try
- 5 volt, 700 mA cellphone charger
- 2 piece hard drive magnets
- wood disk to space the metal washer and magnets off of the fan motor, otherwise the pull of the drive magnets "froze" the fan in place
- 1.5" stir bar

I used double sided tape to hold the pieces in place while I was adjusting everything for rotational balance and height adjustments.

Now the pics of the set up:

Business card case. I liked the transparent and hinged top which makes adjustments a breeze and best of all, it was free! So look around for that cigar box or other cool containers that you can use. Get creative!

I mounted the fan with the screw heads underneath the housing as this allowed me to adjust the height of the fan with the nuts.

Some hard drives come with one piece magnet, some with two. Reading about others experiences, I feel that the 2 piece set up made it easier to find a balance point that's in line with the fan center of rotation as opposed to the one center mounted magnet. But YMMV.

I wound up with about a 3/4" gap between the top of the hard drive magnets and the stir bar.

I used a flower vase as the yeast flask because it had a nice flat bottom.
Oooh, cool blue light switch. :rockin: This is with a liter of water. I still had a little more on the potentiometer to go to 11 (but it's not really needed).

With the yeasties in suspension. I used a mouse pad underneath the stirplate to absorb the vibration and lessen the noise. I didn't really go all out in creating a violent whirl pool.

I would be glad to answer any questions about my set up. Fantastic thread and my thanks to Anthony Lopez for starting it.

 

[tincob]

now posted with pics

 

[passedpawn]

Nice! That'll grow some yeast for sure!

 

[huknbuk]

Let me preface this by letting you know my electrical/mechanical knowledge is pretty much non-existent. I read through the entire thread (quickly) so I my have missed my answers.
First, when I cut open my power supply (old cell phone charger) It had four insulated wires: red, green, black, and yellow. How should I be using these?
Also, I think I may have run into an issue alluded to earlier. I read 10/32 as the diameter for the bolts, which I took to mean 5/8", which based on the above replies and, well, looking at my fan, I assume is incorrect. Do you know what the diameter of the bolts should be?
Thank you.

 

[camiller]

... I read 10/32 as the diameter for the bolts, which I took to mean 5/8", which based on the above replies and, well, looking at my fan, I assume is incorrect. Do you know what the diameter of the bolts should be?
Thank you.

A #10 bolt. 32 thread pitch. You could use 24 pitch as long as you buy nuts with the same pitch. 32 is probably more common. A #10 bolt is 0.1900 inches. Which doesn't matter because at the hardware store the package will say #10.

 

[Anthony_Lopez]

Let me preface this by letting you know my electrical/mechanical knowledge is pretty much non-existent. I read through the entire thread (quickly) so I my have missed my answers.
First, when I cut open my power supply (old cell phone charger) It had four insulated wires: red, green, black, and yellow. How should I be using these?
Also, I think I may have run into an issue alluded to earlier. I read 10/32 as the diameter for the bolts, which I took to mean 5/8", which based on the above replies and, well, looking at my fan, I assume is incorrect. Do you know what the diameter of the bolts should be?
Thank you.

I chose the #10 32 thread bolts because that was the most common diameter I found while going through computer fans.

Note: I edited the original post to highlight the confusion with #10-32 (10/32) bolts.

As for the power supply, you don't need to take the "wall wort" apart. You just need to cut off the connector at the end of the cord to expose the wires. You should only need red and black. If black doesn't work, I would try green as your negative.

 

[huknbuk]

Yeah, I'm sorry, I worded that poorly, I did just cut off the connector. So unless it doesn't work, I should use the red and black wires and ignore the green and yellow ones?
By the way, thank you for the write up of this info.

 

[starsailor]

Hey I built one of the these and it was pretty easy. My only variation is that I found some 1/3" dia. rare earth magnets at the local Ace Hardware and I used those instead of ripping up a hard drive. It works like a champ!

 

[goose_on_fire]

Yeah, I'm sorry, I worded that poorly, I did just cut off the connector. So unless it doesn't work, I should use the red and black wires and ignore the green and yellow ones?
By the way, thank you for the write up of this info.

Personally speaking, I'm much lazier than that. I leave the wall warts intact (so they don't have to travel with the device) and buy something like this. Just make sure you get the right size.

There's a whole page of Kobiconn panel-mount DC power jacks for about a buck each right here.

All that said, though, if you measure the correct voltage between the black and red wires (might read a little high with no load) then yeah, you're probably fine. Tape the others up so they don't short out, and give it a shot.

 

[user 40839]

Friggin' brilliant stuff. The only hiccup I encountered was with Radio Shack's @#$# wire clips, their "crimpability" was suspect, to say the least!

The cheapest stirplate normally goes for $45 or so, and that has no adjustable speed control. I was able to bang this out, as advertised for under $30 - and could have done it cheaper if I could remember where I put the @#$# case fan I had, and didn't have to buy another one.

Thanks a million for the instructions!

 

[Anthony_Lopez]

I'm glad you liked it!

 

[user 40839]

Not sure if it's the magnet I'm using, but with a 5v ac adapter, mine runs way too slowly - can't get the vortex to really get going with 800ml in the flask. When I tried a 9v it was way too fast, and the stir bar wouldn't stay centered and spinning. So now I need to rummage around and find a 6v or something similar to try and hit that sweet spot!

 

[krops13]

You don't really need a vortex. As long as everything is spinning your ok. It's mainly to keep yeast in suspension. I had to raise my magnet with a spacer to get it to work properly.

 

[user 40839]

You don't really need a vortex. As long as everything is spinning your ok. It's mainly to keep yeast in suspension. I had to raise my magnet with a spacer to get it to work properly.

Yeah, but when it comes to gadgets - especially ones you make yourself - what you "need" and what you "want" tend to butt heads!

I managed to snag a 6v ac adapter that my wife left lying around - her own fault - and it does the trick nicely. The rush of testosterone also made me buy a more... manly switch. This way, anytime I cultivate yeast, I can feel like I'm launching a nuclear warhead! Here she is, in all her final glory. Thanks again for the outstanding tutorial, Anthony - although would love to know how you got a 12v AC adapter to work, since when I used 12v in there, it flung the stirbar before it got up to speed on the lowest setting!

 

[Anthony_Lopez]

Thanks again for the outstanding tutorial, Anthony - although would love to know how you got a 12v AC adapter to work, since when I used 12v in there, it flung the stirbar before it got up to speed on the lowest setting!

I found that it's a balancing act between magnetic force and voltage. The more magnets you use, the better it will hold the stir bar. This allows you to use a higher voltage. With the current setup I have, I can make a 1" wide vortex touch down on the bottom of my 2L flask using a 1.5" stirbar. It's so loud I can hear it in my bedroom...