Question about using a stir plate

[petrolSpice]

I just made my own stir plate for around $20 and it works pretty well. When it's on it will make a vortex in the middle of the liquid. If I turn it up high enough the vortex will get bigger/deeper and eventually hit the stir bar and it will throw air bubbles into the wort. Is this what I'm aiming for or is a gentle vortex that doesn't reach the bottom good enough?

 

[Transamguy77]

All your looking for is to keep the yeast in suspension, it doesn't need to be a crazy vortex.

 

[beergolf]

A small dimple is all,you need. Just keep the yeast swirling.

 

[sudbuster]

I just made my own stir plate for around $20 and it works pretty well. When it's on it will make a vortex in the middle of the liquid. If I turn it up high enough the vortex will get bigger/deeper and eventually hit the stir bar and it will throw air bubbles into the wort. Is this what I'm aiming for or is a gentle vortex that doesn't reach the bottom good enough?

No. Turn it down to just stir the yeast. That is all that's needed. Cheers..

 

[petrolSpice]

Thanks guys. I may need to reduce the voltage even more. It's a 12V fan but even at 7V it will create a heck of vortex. It's a 12V power supply but the rheostat will only get it down to 7V.

 

[Munchkin]

whats the size of your flask and stir bar? My vortex wasnt that crazy with a 1" stirbar in a 2L flask @ 12v

 

[Zepth]

Thanks guys. I may need to reduce the voltage even more. It's a 12V fan but even at 7V it will create a heck of vortex. It's a 12V power supply but the rheostat will only get it down to 7V.

You say power supply. As in one from a computer? The red wire inside is a +5, hook it up to a ground (black) and give it a shot. If for some reason that's still too fast, try the orange +3.3v. In my experiences, a standard computer fan won't turn at that point but all are different after all. Something really wacky going on? Use the +5 as your "hot" wire and the 3.3 as your ground and bring the thing down to 1.7!

If not using a computer power supply you could go the a hobby shop and get a resistor to use in line with the motor of choice. Or get another motor of choice, wire it in series and use the rheostat that you've already got to bring the effective voltage down to 3.5 if need be.

 

[petrolSpice]

whats the size of your flask and stir bar? My vortex wasnt that crazy with a 1" stirbar in a 2L flask @ 12v

I was testing with with a 50mm and 40mm stir bar, for some reason the smaller ones I have wont center on the magnet. I was testing in a stainless stock pot. With a flask the height of the water should be much higher so perhaps the vortex wont reach the stir bar in that case.

You say power supply. As in one from a computer? The red wire inside is a +5, hook it up to a ground (black) and give it a shot. If for some reason that's still too fast, try the orange +3.3v. In my experiences, a standard computer fan won't turn at that point but all are different after all. Something really wacky going on? Use the +5 as your "hot" wire and the 3.3 as your ground and bring the thing down to 1.7!

If not using a computer power supply you could go the a hobby shop and get a resistor to use in line with the motor of choice. Or get another motor of choice, wire it in series and use the rheostat that you've already got to bring the effective voltage down to 3.5 if need be.

I should have clarified; its a standard 12V 500mA AC to DC plug in power supply / adapter with a size 'M' coaxial connector on the end, much like this. I have other power supplies I can try with various voltages. I did try a 9V supply, but again the min voltage I could obtain was 7V, max was 10-11V.

 

[trentm]

More air = more yeast growth. Take a look at this experiment: http://braukaiser.com/blog/blog/2013/03/25/stir-speed-and-yeast-growth/
Let it rip.

 

[Zepth]

First let me say that I am not an electrician. I do not possess an engineering degree, or any degree for that matter. Anyone possessing an electrical degree is not only welcomed but encouraged to correct me. Now that we have that out of the way, onto business!

I believe those type of adapters that have a fixed output work on a percentage basis which is dependent on the ratio of primary and secondary wire coils inside. The amperage is dependent on the quantity. Eg: 10% of 120v = 12v. With this you could try to hook a regular old dimmer switch up to the custom circuit BEFORE the adapter. This would IMO do one of two things: reduce the input voltage going to the adapter, meaning the % reduction would be more appropriate for your needs (50v to "part that goes into wall" = 5v at output). Or it would cause the thing to not work at all. Possibly ever.

Wiring diagram:
Wall -> dimmer switch -> adapter -> stir plate

 

[Fermented_minds]

All your looking for is to keep the yeast in suspension, it doesn't need to be a crazy vortex.

+1! Right on!

Sometimes I see people cranking it up all the way and the reality is that the sheer force from a really strong vortex can actually damage cells, in which case you're doing yourself a disservice.

All that is required is to keep cells in suspension in constant contact with nutrients, and to allow for gas exchange.

Cheers!

 

[petrolSpice]

Tried out a 6V power supply and combined with the rheostat I can get a range of 3-6V into the fan which is good for a slower gentle spin.

I am curious about that link above where he showed that the faster spin will grow more cells, almost 40% more between a very slow spin and very fast spin.

 

[Fermented_minds]

I am curious about that link above where he showed that the faster spin will grow more cells, almost 40% more between a very slow spin and very fast spin.

This absolutely is true. The more aeration you get (up to a point), the more healthy yeast you will get. However, vortexing over a certain speed will result in forces that are great enough to potentially damage cells, not to mention the friction of the stir bar and the surface of the flask can also damage cells. It's the reason that in any industry that grows cells for sale or research use, the mixing is almost always done via an overhead stirring blade or an orbital shaker (for small volumes).