My DIY Stir Plate

[bluenose]

Finally getting my arse in gear and putting together a stir plate.

I'm making my box out of wood because I have some on hand

Parts prepared and ready for assembly (mostly)

P1010974.JPG

What I have here is 1/4 plywood cut into two pieces that are 10" x 10". I went with this size so my 5L flask will fit on it.
>1" x 4" cut into two 21.5" lengths. The will both be cut in half to bake the front, back and sides of the casing. There are two 1/4" channels cut into each one a 1/4" from the edge. These channels are >Where the 1/4" plywood will slide into to form the top and bottom of the casing.
>There's a fan a salvaged from an old PC
>A 12V DC wall wort

Grooves that are 1/4" wide, by 1/4" deep, spaced a 1/4" from the edge. Cut with a table saw.

P1010975.JPG

Closeup of fan with a rare earth magnet from a PC hard drive JB Welded to the PC fan. It is rated at 12V DC and 0.40 Amps.

P1010976.JPG

Here's the wall wart I have.

P1010978.JPG

I have two questions I'm hoping the collective can help me with:
1) What specs should I look for in a rheostat?
2) Where can I find said rheostat?

I'll post more pictures once it's fully assembled.

[Keith]

Take some good notes on this (with pics). I'm really curious.
I know it's on my things to do soon. Fermentation chamber and starter.

[LeafMan66_67]

Two items I see - will that magnet spin the stir bar through a 1/4" plywood and a flask? Also, your wall wart is only putting out 5VDC and your fan is 12VDC. Have you checked to see how fast the fan will spin with the magnet and stir bar attached?

[bluenose]

Two items I see - will that magnet spin the stir bar through a 1/4" plywood and a flask?

Yes, I tested it manually, but not in liquid

Also, your wall wart is only putting out 5VDC and your fan is 12VDC. Have you checked to see how fast the fan will spin with the magnet and stir bar attached?

That could be a problem... definitely points to ponder

[RossBee]

When I build mine, I used a plastic bucket to mount the fan - I know, not the sexiest looking thing, but the plastic is quite thin and strong. I used two rare earth magnets on the fan in conjuction with a 1" stir stick.

The fan (120V) came from Princess Auto (about $15) and I used a dimmer switch (~$4) for the speed control. Except for the bucket, the major bits came from Princess Auto.

The only advise I would suggest, go big on the magnets. Mine works fine at medium speed, and is unreliable at high speed, the stir bar seems to "jump the magnets".

Also, if you can use a clear bucket, such as a square one that screws come in, it let's you see what's going on inside the thing. Again, not sexy, but it does the trick.

[bluenose]

I've seen some people have used cigar boxes, but the wood is probably thinner than 1/4" plywood. I'm partly going for looks, but mainly went this way for size, stability, and the materials are at hand.

I picked up a 12 VDC .6 amp converter, so it should be enough to power the fan. Whether the magnet is strong enough to move the bar in a flask full of liquid remains to be seen. I'm going to go ahead with this configuration since the hard part is already done, and the materials were all free. I still need a rheostat. I might have to order one online if I only knew what specs I should be looking for. If it's not powerful enough I will try again.

[LeafMan66_67]

I used a tea box from the Dollar Store.

[bluenose]

I need electrical advice for my stir plate. Here's how I wired it up last night and when I plugged it in it blew the breaker:

IMG_20150424_104157.604.jpg

There were other things plugged into the circuit and I didn't try plugging it into another circuit, but I think it's more likely that I have a short somewhere. Does anyone see anything obviously wrong with this circuit?

The overall enclosure is made of wood, but I put the GFCI outlet in a metal box. I may pick up a plastic box today and try that instead.

[RossBee]

I built mine using a 110V projector fan from Princess Auto and a dimmer switch, i.e. no need for a transformer, mounted in a plastic bucket. Not fancy, in fact, rather ugly, but it works.