Tight Arse Stir Plate

[christmas]

I pimped mine out with a glowing blue fan and a six buck ebay temperature display

 

[OneEye]

I'm throwing together the bits and bobs to get a build for myself going. I've done a few simple circuits before but just have one question for those out there who have a bit more of a grasp on this than me.

Following along with LC's circuit, it calls for a 680Ohm Resistor. From what I already have laying around, I have 6 100 Ohm and 1 80 Ohm resistors. If I place them together in series will that give me the same result?

 

[leiothrix]

Yes it will, resisters values are additive when placed in series.

 

[OneEye]

I thought so but wasn't 100%. I've knocked it all together and she's working a beauty!

 

[christmas]

When I turn the speed down to a reasonable level, mine emits a horrible high pitched noise. Pretty much anything under full speed will get it.

Anyone know why this could be?

I think it's because I tried to make mine all flash and used a fan with LEDs in it, and they don't take kindly to being dimmed.

I might try stuffing the box full of foam to try and limit it a bit. Failing that, starters are gonna have to be made in closed room somewhere. I really don't feel like replacing the fan, this thing has already been a whole load of dicking about.

 

[blotto]

I think it's because I tried to make mine all flash and used a fan with LEDs in it, and they don't take kindly to being dimmed.

I'm not sure why it would be making noise but I cut the cables to the LEDs on my fan in my brew fridge because light is bad for the yeast, you could give that a go?

 

[NewtownClown]

I'm not sure why it would be making noise but I cut the cables to the LEDs on my fan in my brew fridge because light is bad for the yeast, you could give that a go?

As far as my limited research has revealed, visible light only has an effect on brewers yeast when grown at/below 12C.
Ultraviolet light actually increases the growth rate of yeast and studies proved that beer ferments quicker under UV, however there is a fine line between intensity and exposure time, the UV will eventually kill the yeast.

From that, I'd argue your little LEDs wont cause harm.

 

[blotto]

As far as my limited research has revealed, visible light only has an effect on brewers yeast when grown at/below 12C.
Ultraviolet light actually increases the growth rate of yeast and studies proved that beer ferments quicker under UV, however there is a fine line between intensity and exposure time, the UV will eventually kill the yeast.

From that, I'd argue your little LEDs wont cause harm.

Fair enough please disregard my uneducated comment. I think I'll still ferment in the dark, in more ways than one it would seem

Christmas you could still try disconnecting the LEDs if you think that might be the problem.

 

[bond]

Just fired mine up, my 5L demijohn has quite a concave bottom, it threw the stir bar until I double stacked extra magnets.

It's quiet enough when the whirlpool is only an inch deep, but quite loud when on full tilt - do flat bottom flasks help with this?



I think I'll remove the potentiometer from the PWM board, and mount it and a DC socket into another piece of perspex - more tweaking first though

The pwm controller I used : DC 5V-40V 3A PWM Controller (ebay)

 

[felten]

Are you using a stirbar with the pivot ring? Apparently they can be quite noisy.

Oh I can see it in the pic, you might want to look at an egg shaped bar.

 

[Wolfy]

Stir bars with a pivot ring tend to be more noisy, however they are probably better on the curved base of the demi john.

 

[yum beer]

View attachment 57477

Just fired mine up, my 5L demijohn has quite a concave bottom, it threw the stir bar until I double stacked extra magnets.

It's quiet enough when the whirlpool is only an inch deep, but quite loud when on full tilt - do flat bottom flasks help with this?



I think I'll remove the potentiometer from the PWM board, and mount it and a DC socket into another piece of perspex - more tweaking first though

The pwm controller I used : DC 5V-40V 3A PWM Controller (ebay)

Hey bond,

how do you have the fan attached to the perspex....

 

[bond]

how do you have the fan attached to the perspex....

http://www.pencomsf.com/mechanical/fan_screws.aspx - Had these which came with fan's I've bought in the past

 

[Aydos]

Wow i just finished reading all of this thread, there is some really good info in here.

Need to stop being so lazy and get mine built!

 

[mkstalen]

I bought the parts to do this build a little while ago, and finally got some time yesterday arvo to put it together (little bloke was sleeping, wife was quilting).

Here's the breakdown:
1 x 120mm PC fan (12v, 0.3A) $2.99
1 x LED dimmer (12-24V, 8A) $3.21
1 x Old power supply (12v, 450mA) Free
10 x 8mm x 1mm neodymium magnets. $1.42
1.2L square plastic container pinched from cupboard. Free (I think they're about $5.)
Screws, wingnuts, and rubber feet things $6 maybe.
Total = $20 tops


Pics in the following galley.
http://aussiehomebrewer.com/gallery/album/1010-stir-plate-build/

(Can't figure out how to easily insert them into this post)

My only question is when I have the dimmer turned down all the way the fan is still running, anyone got any ideas why this might be? I thought it'd be off when turned right down...

 

[Amber Fluid]

It is possible the "knob" to control your fan is not set correctly....
Pull the knob off (pardon the pun) then turn the fan down as far as it will go with your fingers. Replace knob and it should be fine.

 

[LethalCorpse]

Most switchmode drivers have a minimum on time for stable regulation. If it's a cheap controller, this can be quite a high duty cycle. The designers of your LED controller may have added a series resistance with your control pot to allow for this, and erred on the side of caution. Either way it's likely to be inherent to your controller and not easy to remove

 

[KingKong]

Quick question my power 12v power supply adaptor. How do i easily know which is positive and which is negative when both are black ? One cord has white dash's on it?

Further im running to a dimmer that says .8 amps my power supply is throwing out 1 amp. Ok or not?

 

[treefiddy]

I think the white stripe is usually positive.

Might be that the dimmer is rated at a maximum of 0.8 amps, but if you're using something that uses less that 0.8 amps (such as a PC fan) then the rating of the dimmer will not be exceeded.

 

[MCHammo]

Just came across this thread, and thought I'd put up my design. Rigged up an old 555 timer I had lying around with a pot, a diode, and a few resistors + caps. I see there is a different 555 design floating around here somewhere. I might as well add mine to the mix.


Schematic for the PWM driver. I used a 100k pot and... can't remember the two resistors. 1k maybe? I'll need to dig out my stir plate later on to check. I've opted for a mosfet to drive the fan rather than a plain transistor. Personal preference - a few less components required, and more efficient.


Circuit board I etched for this purpose. About 25x30mm in size.


Assembled plate (with a few extra switches, plugs, etc.) You can see the PCB between the pot and the fan. Powered by an old PC power supply that I turned into a bench-top power supply... At least until I can be arsed looking for a suitable plugpack. I'm sure I've got one somewhere.