DIY stirplate FAN SPEED

How do I slow this mother down?

Bought a DIY style plate off of ebay to save myself from learning basic electronics. Well... ****. It doesn't work. Keeps throwing the bar. I believe I could fix the problem by slowing down the fan because the slowest speed on the dial is too fast. Not sure how he made it but the dial travels about 80% before the fan even kicks on. Here are the specs in the ebay ad, any thoughts?

These custom built stir plates are made with all new components. They are assembled using Neodymium magnets, a 12 vdc power supply and a brand new 80 mm computer fan. It has a variable speed control and a separate on/off switch on these units. All components are soldered for the best performance and reliability. I will also include a 1" x 1/4" stir bar or 1 1/8" x 1/4" stir bar!

Variable speed control my ass. There is one speed.. FAST.

There is no circuit board like I see in some of the pictures. Just the knob, on off switch, and some wires.

If I need to add a resistor, how do I do that?

Right now I have my flask gently tipped up with a pencil and the side with the bar on the center of the fan and it is just hopping around. Is that good enough to keep the yeast in suspension?

Well, I'm not sure which one you have, but a couple of thoughts..

• Use a smaller power supply.
• I use a potentionmeter (variable resistor), part #271-215 at radio shack to adjust the speed (power) going to the fan.

You "could" add a resistor, but it would be difficult to guesstimate which size you need. Here is a how the wires are hooked up on mine:

Add a second pentomenter (also called a rheostat I think) to it. Or you may be able to replace the orginal one.

Here is another thought. Your magnets may not be polarized correctly. Take your stir bar and slowly slide it accross the top of your stir plate where the magnet is on the fan. Don't let the fan move and keep the stir bar in the same direction. Do this for about 20 strokes. Then put it in your flask and give it a whirl.

I had a bar that kept getting thrown, and it was due to the polarity issue.

I will try the polarity thing but due to the tornado touching down all the time I think it is more speed related. How would I go about adding a second pentomenter? how would the two dials work together?

Ok guys I'm working on my stirplate. I haven't added the potentiometer yet but I can't get my stir bar to spin at all. It wiggles a bit and then like dances away. I am HOPING that slowing the beast down will fix it? I am using 12V power supply and a 12V GPU fan. I got a project enclosure and a potentiometer and I'm gonna try to wire it like this. We'll see! I'll post results soon. If I fail at this I'll post a video so you guys can help me out! I started with rare earth magnets from harbor freight (they were tiny) and now I've switched to hard drive magnets, but they seem quite thin and not as hefty as some photos I've seen.

12 volts to a 12 volt fan will want to run at normal fan speed.
One suggestion - find a wall wart you're not using that has an output of 6, 7.5 or 9 V and try that... The variable resistor (potentiometer, rheostat) will be able to do a better job.

Hang Glider said:

12 volts to a 12 volt fan will want to run at normal fan speed.
One suggestion - find a wall wart you're not using that has an output of 6, 7.5 or 9 V and try that... The variable resistor (potentiometer, rheostat) will be able to do a better job.

Click to expand...

ok I have one of those. What is the "symptom" of too fast fan? Does it look like the stir bar ain't doing much? I get basically no activity except the stir bar floats to the outer portion of the flask unless I hand spin the fan and then i can get the stir bar to spin a wee bit. I'll try potentiometer and lower voltage and if still no dice I'll post video.

Ok. I wired my potentiometer based on the diagram above and now the switch works, but it only turns it on/off. I have to turn it to max and then the fan turns on. This is true with both 12V and 6V adapters, which I thought was weird. Any suggestions? I can send a pic but it looks like the one above, I just didn't solder it yet. What happens is if i turn the fan off and on a lot, trying to keep lower speed, the stir bar starts to spin up, but then it gets thrown either from too much speed or from the fan turning off.

By the way, this is the fan I am using, it has red/white/black wires. I'm not sure what the white wire is for because red is power.

FWIW, here's mine, pretty much as simple as it gets. I've found that ~4.5v works well for 1-2L, and ~5v works for 2-2.5L. Just used old cell phone chargers, an old computer fan, and some salvaged rare earth magnets. $8 and I got 2 stirplates (costs for bottle and stirbar)

Ask for your money back if it's not as advertised. Simply adding another resistor or a trimmer pot will probably just burn those components up if they're not valued at several watts.

Derrin said:

Ask for your money back if it's not as advertised. Simply adding another resistor or a trimmer pot will probably just burn those components up if they're not valued at several watts.

Click to expand...

I'm not sure what this means. Are you saying my potentiometer is defective?

Picobrew said:

I'm not sure what this means. Are you saying my potentiometer is defective?

Click to expand...

I guess you're probably referring to the OP!

Now I'm wondering if it is just my fan.. maybe it only likes to run at full clip with no resistance in the pathway? I don't really get it. I tried reversing polarity on my power supply and thats definitely not the issue. It's weird, it kicks in at full open on the potentiometer but not otherwise.

Here's my AC version FWIW:







This was an early build. It's evolved some since then. I'll try to post a step by step the next time I build one for a friend. I've got a request pending for a double fan design, so that will probably be the next one. I build these at cost for my brewing buddies that want them. The components cost about $20 if I have to buy everything. The double one should come in at around $30. That's using all new parts.

Pico - you could have several things going on...
To isolate, forget the stir bar and get the fan to work like you want it...
1) magnets may be interferring with fan. Take magnet off, does fan work now? if so, separate magnet and fan with some kind of spacer.
2) fan is only hi-speed or zero? perhaps the potentiometer (dial) is wired wrong. Resistance has to go thru it. If the wire is in the wrong place, it is "jumping" to the full, not slowing down going thru.

there - now you have two things you can check on...

j_jones84 said:

How do I slow this mother down?

Bought a DIY style plate off of ebay to save myself from learning basic electronics. Well... ****. It doesn't work. Keeps throwing the bar. I believe I could fix the problem by slowing down the fan because the slowest speed on the dial is too fast. Not sure how he made it but the dial travels about 80% before the fan even kicks on. Here are the specs in the ebay ad, any thoughts?

These custom built stir plates are made with all new components. They are assembled using Neodymium magnets, a 12 vdc power supply and a brand new 80 mm computer fan. It has a variable speed control and a separate on/off switch on these units. All components are soldered for the best performance and reliability. I will also include a 1" x 1/4" stir bar or 1 1/8" x 1/4" stir bar!

Click to expand...

when i built mine I found the 12v power supply was too much even with the RS potentionmeter it spun to fast never threw the bar but was sucking the vortex all the way down. I went with a 9v supply from an old cordless phone and it now works perfect

At 5 volts my fan draws 3.6 watts, at the readings of 14.6 volts on the 12 volt output cube I read 10.51 watts. Both way over the 3 watt capacity of a pot unless it is a big pot from a surplus store or a proper wattage large Ohmite wire wound resistor for your control. They are not cheap hence the ECROS power regulator supply and i;m done with it.

cat22 has it down but I didn't have any 120 volt 4" square fans, I gave a bag full of them to the high school electric class. Stupid me had 38 should of kept one then added a dimmer. Oh well.

Man that 110V is awesome! I have one of those myself and now that I have seen someone else put it together I have to get off my lazy ass and build mine!

Guys,

Here's the latest innovation I came up with to mitigate the problems with speed control on these fans. Basically what you want to do is add some resistance for the motor to work against. I did this by building a "flywheel" and mounted it to the fan face. The flywheel is simply an oak disc that I cut from 3/4" stock using a hole saw. The flywheel disc is also the holder for the rare earth magnets. The weight of the flywheel provides some resitance to spinning which helps tame the fan. The flywheel also helps to prevent stalling when voltage fluctuations occur as sometimes happens when other appliances on a circuit turn on and off. I drilled holes into the wooden disc to hold the magnets. They are an interference fit so no glue is required. Another advantage of this "flywheel" design is that the magnets are reasonably close to the same density as the oak. What that means is that slight misalignment of the magnets won't create excessive vibration as can sometimes be the case when simply trying to glue the magnets to the fan or to a washer. I used 3M 77 spray adhesive to attach the flywheel disc to the fan. This adhesive works well because it is tacky enough to hold the disc to the fan, yet allows you to move it for alignment purposes. You can spin the fan by hand and it's easy to align it very precisely. The adhesive doesn't set up completely for hours, yet holds the disc firmly enough to operate the stir plate immediately. I used a 4-1/2" hole saw which cuts a 4-1/4" plug. This happens to be exactly the diameter of the fan from blade tip to blade tip. That makes it very easy to position the disc. Here's a pic of the fan with the "flywheel". You will see some hot melt glue around the magnets. I realized later that this was not needed:





The magnets are 1/8" dia x 1" long. These work really well and they are relatively cheap.

This flywheel design should work with either AC or DC fans. You may find that you need to use a higer voltage wall wart to start the flywheel from a dead stop, but I think you will also find that the speed is much more controllable. I can dial mine down real slow if I want to and I can maintain it at that speed easily. I can also dial it up to the level you see in the earlier post that was taken pre-flywheel.

Now remember, you heard it here first! Mark my words. Someday every DIY muffin fan stir plate will be equipped with Catt's flywheel magnet holder design.

Enjoy!

j_jones84 said:

How do I slow this mother down?

Bought a DIY style plate off of ebay to save myself from learning basic electronics. Well... ****. It doesn't work. Keeps throwing the bar. I believe I could fix the problem by slowing down the fan because the slowest speed on the dial is too fast. Not sure how he made it but the dial travels about 80% before the fan even kicks on. Here are the specs in the ebay ad, any thoughts?

These custom built stir plates are made with all new components. They are assembled using Neodymium magnets, a 12 vdc power supply and a brand new 80 mm computer fan. It has a variable speed control and a separate on/off switch on these units. All components are soldered for the best performance and reliability. I will also include a 1" x 1/4" stir bar or 1 1/8" x 1/4" stir bar!

Click to expand...

That sounds like a kit with just a pot for voltage control plus the pot is way to high in resistance if you have 80% useless knob turning before anything happens then almost full speed.
Then you stated 80 mm that's only a 3" fan, i'm measuring 4 11/16" on the fan bodies I have. What all came in this kit in parts may I ask?