Home made stir plate

DandyMason · July 05, 2012, 06:33:45 PM

Just trying out my stir plate I built... something weird is going on...

I have one of those hard drive fans with a 9V power supply. The stir bar starts to spin and then gets thrown to the side....

Is 9V too high?

Richard · July 05, 2012, 06:47:25 PM

Sounds it - try building a potential divider with a variable resistor and putting that in the mix... failing that, get a stronger magnet.

Also my understanding is that the stir bar should be spinning around its axis - maybe you've got it off?

DandyMason · July 05, 2012, 06:56:41 PM

Ahhh true, Maybe I dont have the magnet centred in the fan... Because I thought I had read of ppl using up to 12V... I could be wrong though.

Ill take a look at the placement of the magnet...

Its weird, WITHOUT water the stir bar spins like it should... WITH water it gets tossed to the side...

brew · July 05, 2012, 06:59:17 PM

Yeah I found 9v a bit too high for mine - I used a spare 7.5v adapter and it worked much better. I also went to The Source and picked up a POT for like $6 - if you hook that up like a switch, you can turn down the speed...

DandyMason · July 05, 2012, 07:11:45 PM

Yeah Im definitely thinking 9 V is too much now... Ill find a 7.5V and swap them...

How do you hook up those potentiometers to adjust speed?

brew · July 05, 2012, 07:27:23 PM

The POT at The Source that I bought looks a lot like the one in figure 5 on this site: http://sound.westhost.com/pots.htm

Figure 6 shows some wiring alternatives. I use mine as a variable resistor...

DandyMason · July 05, 2012, 09:53:17 PM

k this is really confusing me now...

I got a power supply that can switch from different voltages... so I was able to try this at a bunch of different voltages. I can sometimes get it stirring without being thrown to the sides at 4.5 volts, but it seems any higher the stir bar just gets sent to the side.

Is it possible that my stir bar is too small for my flask? I ordered one of the small stir bars and have a 5L flask... so it seems like its pretty easy for the stir bar to avoid the magnet on the fan... Any ideas? Maybe a longer stir bar? or a stronger magnet?

DandyMason · July 05, 2012, 10:05:08 PM

False alarm guys, Im a complete idiot hahaha

The fan/magnet was simply too far away from the flask... I had it mounted to the bottom of my stir plate instead of the top...

Anyways... All voltages are working now... even 9 and 12 V although they are really vigorous.

Thanks for the help!

brew · July 05, 2012, 10:27:43 PM

Glad to hear it man - post a pic if you can...

DandyMason · July 05, 2012, 10:52:32 PM

Sure thing, it isnt pretty though

DandyMason · July 05, 2012, 10:55:18 PM

It gets the job done though... Might at some point invest in a nicer box when this one gets wet hahah

brew · July 06, 2012, 08:34:23 AM

Awesome - I love it!

pliny · July 06, 2012, 08:51:44 AM

Perfect man.
I've seen some folks use a wooden cigar box.

jeffsmith · July 06, 2012, 10:39:52 AM

Nice work! I've got mine in an old plastic zip lock container. I'd been thinking about picking up a weather proof electrical junction box from Kent/Home Depot for a little more solid, long term solution.

DandyMason · July 06, 2012, 12:33:26 PM

Thanks guys, yeah a cigar box would be perfect! and Jeff I had thought of using some tupperware, still an option.

But this box is strong enough for now anyway, until I find a better one... I was thinking of heading to the dollar store and grabbing one of those small boxes ppl use for gift wrapping.