PWM Stir Plate Plans

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HenryVance3

HenryVance3

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I have been searching for good PWM plans and found a some that are worth sharing. For those who are wanting modulated overkill click this link

http://www.overclockers.com/pwm-fan-controller


I went the route of so many before me with the project box from radio shack and some fan I scrounged along with Hard drive magnets. I also found a lot of DC plugs from 6 volts to 12volts with a type M plug. This is important because you can get a female adapter at Radio Shack pictured in the back right corner of my box for a clean connection.

I will post more as my project continues.....

What is the best way you all have found to balance the magnet on the fan?



______________________________________________________

"Are you gonna be working on your Brew Stuff? Yes Honey, I will be working on my Brew Stuff."

PWM 004.jpg


PWM 003.jpg
 
Just for all the people out there that dont wanna solder a board, can we get a close up of the prototype power, so we can see which legs are on each row and column?
 
well I expect he didnt write the linked article, but he made his own, so I wanted to see a close up of his board
 
I am in the process of soldering it still. I still need one mCapacitor #3 and then I will get to try it out...

PWM 007.jpg


PWM 008.jpg
 
This actually is turning out to be easier than I anticipated. So far only like two hours in to the project. (which on one hand is disappointing because it is winter in Alaska and this was supposed to kill more time, oh well more time to brew...)
 
A standard house wall dimmer and plug in a 2-gang box is a ton easier and can be built within a matter of minutes. Wall dimmers are nothing more than PWM circuits.
 
jcaudill said:
A standard house wall dimmer and plug in a 2-gang box is a ton easier and can be built within a matter of minutes. Wall dimmers are nothing more than PWM circuits.
Click to expand...

I considered that and decided to make my life more complicated by learning basic breadboarding :) +1 for keeping it simple with the dimmer.
 
jcaudill said:
Wall dimmers are nothing more than PWM circuits.
Click to expand...

normal dimmers are only rheostats, and not what you want to drive a motor with. there are PWM dimmers, but they are normally more expensive, and you need to make sure what you are buying is actually PWM, and not a simple resistor. they arent all PWM.
 
The cheap rotate on/off dimmer from Walmart is a PWM based dimmer... I've validated this.
 
I use the pwm pins on my arduino fermentation controller :). I didn't really do anything to balance the magnets any better than visual inspection. I did however cut the blades off the fan so it would spin more easily.
 
I just finished a stirplate build using one of these:

http://www.ebay.com/itm/12V-40V-10A...=250907796046&ps=63&clkid=3709609597523364092

It works great with very smooth control. I took the motor control with wire leads to a surplus store and tried fans and power supplies until I was content with the 24V fan. It worked with 12V/18V/24V power supplies and only the top speed was affected by the different supplies, the fan turned off with all of them. Here are pictures of the assembly and some initial testing. I've picked up a 50mm stirbar and it stirs everything I've put on it so far. The magenet is from a server hard-drive.

Stirplate_1.jpg


Stirplate_2.jpg


Stirplate_3.jpg
 
I've got my fan set up with a potentiometer and I have good speed control. I'm using regular hard drive magnets, but all my stir bar will do is jump around, I can't make it spin. Is there some trick to speed or magnet placement? I have one magnet glued to the motor and another one just stuck to it so I can easily remove it if that's my problem..
 
The biggest difference I am seeing between the simple potentiometer and a PWM is that the PWM drives alot harder and stirs at low speeds, without it my fan bogged out on the low end.
 
I had 3 magnets and experimented with the quantity and positions by putting velcro on the motor & magnets (pic below). A single magnet seemed to work the best for me and I left it velcroed because it's not going anywhere and is adjustable. I had the best luck with the fan located as close as possible to the lid without having the magnet scrape.

IMG_1946_small.jpg
 
corkybstewart said:
I've got my fan set up with a potentiometer and I have good speed control. I'm using regular hard drive magnets, but all my stir bar will do is jump around, I can't make it spin. Is there some trick to speed or magnet placement? I have one magnet glued to the motor and another one just stuck to it so I can easily remove it if that's my problem..
Click to expand...

Getting the placement right is important. It's also important that it is balanced properly or you'll put stress on the fan motor along with created a very choppy stir. It sounds like you've got one of the two problems. Two round magnets might be easier to work with and placed from the middle evenly spaced the length of your stir bar.
 
HenryVance3 said:
The biggest difference I am seeing between the simple potentiometer and a PWM is that the PWM drives alot harder and stirs at low speeds, without it my fan bogged out on the low end.
Click to expand...

This is a very good point. I've found most potentiometer/rheostat based solutions cannot spin the fan slow well at all. They can make a very neat vortex but their range of adjustability typically isn't good. Most people don't realize that you don't really need to be spinning fast at all - just enough to get the starter moving.
 
I am currently using a pot only and it's working ok. Had trouble with bar being thrown, but if I keep the speed down, and center the flask, it works great.

But I've built a PWM circuit from the FK804 kit and it can REALLY improve the range of speed control! I'm currently collecting all of the parts to make a bunch of these, since I have friends who need stirplates, and the same circuit can be used to control a boil kettle (though I haven't gotten that far yet) with a simple capacitor swap and a relay.
 
DSmith said:
I just finished a stirplate build using one of these:

http://www.ebay.com/itm/12V-40V-10A-13-KHz-PWM-DC-Motor-Speed-Controller-w-Knob-/260878011175?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26otn%3D5%26pmod%3D250907796046%26ps%3D63%26clkid%3D3709609597523364092

It works great with very smooth control. I took the motor control with wire leads to a surplus store and tried fans and power supplies until I was content with the 24V fan. It worked with 12V/18V/24V power supplies and only the top speed was affected by the different supplies, the fan turned off with all of them. Here are pictures of the assembly and some initial testing. I've picked up a 50mm stirbar and it stirs everything I've put on it so far. The magenet is from a server hard-drive.
Click to expand...

So you need a power source, case fan, and stir bar in addition to the controller right?

What are you using for the dc power source? I have an old charger for a cordless drill, would that work?

How do you wire it all up?
 
HenryVance3 said:
You will also need switch. What is the power rating of your supply cord?
Click to expand...

I have one that could be borrowed but not repurposed (still have the drill) that is 18.2v 210mA. I also have a lawnmower battery charger that is 13.2v and 140mA. I probably have some other things around too if I look a bit harder. Maybe a couple cellphone chargers too.

What sort of mA do I need?

I have plenty of switches no problem.
 
Most fans are 12 volt or less, up to 200 miliamps. I would try to find a 12 or 9 volt cord if you can.
 
I totally agree that nothing is needed except a power supply, motor control (I figured why not pay $12 for a pre-built PWM one) & fan. All that should work crudely wired up before incorporating extras like a switch or LED. The wiring is simple and clearly labeled on the circuit board terminals. The magnet(s) and stirbar are essential at the end of the project.

I started with a standard DC female power jack wired to so I didn't have to cut the end off my power supply for testing. My first test with a 12V power supply (which metered at 20V, no load) and 12V fan was a failure. I couldn't get the fan to turn off and the top speed was way too fast. That fan in now in my freezer set-up with a 6V power supply hardwired to it. A 9V power supply would have solved that or incorporating a 5W resistor to decrease voltage to the fan. But, I went to a local electronics store and experimented until I found a fan (24V) and power supply that worked without needing to incorporate resistors and potential heat issues.
 
DSmith said:
http://i177.photobucket.com/albums/w225/smit1121/IMG_1946_small.jpg[/IMG]
Click to expand...

With your setup you used a 24v fan, where as most computer fans are 12v. The PWM you listed in your earlier post only goes from 12v to 40v. So my question is you have to use a 24v fan other wise you wont be able to drop the voltage low enough, so it would spin slow with a 12v fan?

Is there a 1v - 12v prebuilt PWM? Is that what you would use for a 12v fan? and what would the amperage draw for a computer fan would draw? A small DC motor should work just as well, right, as long as the magnet wouldn't interfere with the motor and be mounted flat and even?
 
The unit is 12-40v input voltage, so you can hook any source voltage from 12-40v and it will handle it. If you have a 12v fan, you hook up a 12v power supply, and then you adjust the pulse width. So that unit posted from ebay would work with a 12v fan as well. Also, if you have a 24v fan, you could hook up a 12v source and it will probably still work. I have a 5v wall wort powering my 12v fan and it works fine for a stir plate.
 
Not the same, but similar. The one posted for less money handles 10A and that one only 6.5. Also, that one uses a 556 chip and the other uses a 555 chip. The 556 is basically a double 555. I'm not sure the advantage of a 556 over a 555, google might be of help on that one.

The price on that one you posted is quite high for what this is. You are probably wanting to get it quicker from a domestic source, but really, if you are in a hurry, Radio Shack should have all the parts you need and be even cheaper.

If you want one that has a remote potentiometer, try THIS ONE

I'd just buy one of those and wait it out. Nobody NEEDS a PWM stir plate right now. I'm that kind that WANTS it now, but I really try to wait when it comes to saving some coin.
 

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