newbie stir plate questions

Hi!

I've done some reading on diy stir plates, and I decided to make one for myself.

I would be very grateful for some feedback about the following build:

1) I found this fan:
http://www.ebay.co.uk/itm/12cm-SATA...797&pid=100033&prg=1011&rk=1&sd=320601500683&

It is a 10-14V voltage & 0.45A current.
I've got 2 old phone chargers but they are:
1) 5v, 550mA
2)5.7v, 800mA

Would it be safe to use the fan with any of the chargers above? Not enough voltage & too high current =(

2) I've noticed that some builds have a potentiometer attached - is that just for regulating fan speed? Is it essential?

3) I'm going to use a 2l flask with the stir plate, following the advice in the yeast freezing thread. What size of a stirrer should I use? 35x6mm or 50x8mm?

Thank you very much for your help!

1) Go to radio shack and buy a cheap adjustable volt wall wort.

2) Yes, it does help regulate the amount of spin from the fan motor. It is a nice feature and I would recommend it.

3) The larger stirrer would be my choice provided it fits down the neck of the flask, with at least 1" clearance on either side at the base.

Thanks!

Will there be any issues if I use a 12V 500mA power source for a 450mA fan?
Also, what resistance on the pot should I look for?

I built mine with a 60mm fan instead of the 120mm you're looking at. I have a friend that fixes computers and he gave me a couple.

Fan is a 12 volt and I'm using a 5 volt charger from an old Bluetooth earpiece.

I have a 2 liter flask and a 1 inch stir bar can bring the vortex to the bottom with 1800ml in the flask. Not constantly to the bottom, but often enough to get air mixing in. I might get a 2 inch stir bar for anything larger than 1 liter.

Thanks for the info!

Am I correct to assume that having a 500mA power source will be absolutely fine for a 450mA fan?

Through Trial and error, I have built two of these now. I also used a 60 mm fan which is just fine. I first tore up a hard drive, but then I found the magnets on amazon.

My first one was built in a plastic screw box, my second was in a cigar box. Both work, but the cigar box looks pretty awesome and makes a great conversation piece.

I used a 5 volt it is wan't strong enough to power the fan. I now have a 10v supply with a 30 volt potentiometer (that's all I could find). The spin doesn't start until I get toward the highest power on the knob, but it does work. My 10 volt will get the vortex from top to bottom using a 1" bar and a full 1000ml flask.

I never looked at the milliamperes of either my fan or power supply, so couldn't tell you. I'd just wire them up and find out. As long as you're watching, if anything starts to smoke, you can unplug it.

Yes a 500mA power supply will work for a 450mA fan.

You need a bigger power supply if your fan Amps is greater than your power supply Amps. If your your power supply is more power than your fan, you're good.

(I'm assuming its a 12V fan, and a 12V power supply)

mChavez said:

Thanks for the info!

Am I correct to assume that having a 500mA power source will be absolutely fine for a 450mA fan?

Click to expand...

Yes, higher amp rating on the power supply is always better.

450mA is how many amps the fan will draw, 500mA is how much the power supply CAN source, not what it will source.

So you can have a 2A source and 450mA fan and have no issues.

That said, another really good place to go if you dont want to spend the money on an adjustable power supply is GoodWill. All of them have electronics sections with tons of loose power cables, you can find power supplys of all shapes and sizes. For example i just bought an old Gamecube 12V 5A power supply for $3 for my pump. Chop the end off and wire it in.

Thanks!