Stir plate - Speed Control

[Codfishhead]

Do I need a speed control on my stir plate?

Picked up a bigass fan from a lab at work and added a plug to it. Took a hammer to a couple spent hard drives and pulled the magnets. Found a box that fits the fan. Bought a pill shaped magnet from the HB shop.

My question is do I need to add a control for speed? Do you guys just blast it as fast as it goes or is there a preferred speed setting best for the yeast?


Thx Jay

 

[Hopper5000]

There's no real preferred setting. I would fill a flask up with water and see what happens. Sometimes the magnet can get flung out of the spinning mode if the plate is going too fast.

 

[Codfishhead]

K thx

I just realized the fan is 120. Direct plug in. I can just add a dimmer switch to it.

 

[chisena]

Add a potentiometer

 

[Codfishhead]

Add a potentiometer

Okay I tried to get one but unfortunately I didn't have the fan with me nor did the 2 people at radio shack know anything. So I bought the biggest they had. Think it may not be for AC.

Will this work together one 110 wall outlet plug?

 

[Hopper5000]

I dunno if that will work, but someone on here probably will. You also are correct that the folks at radioshack are somewhat useless when it comes to this stuff.

 

[jwelch1103]

The label says 250vdc which means direct current, I don't think this will work with alternating current.

Radio Shack is not what it used to be, it should be called RadioPhone Store or something. This past summer I needed a set of hemostats to hold a pair of stiff wires together for soldering. I went to the local Radio Shack and asked the young male clerk if they had any hemostats. He gave me a somewhat dazed look and said he didn't think so and that he had never heard of anything like that. I replied are you sure, they are listed on your website. He asked the manager, a nearly middle aged female and she in other words said the same thing. Then I told him some people might call them "roach clips" and they kind of look like scissors. I could see the light come on in his head and he said yeah I think we do then led me right to them! True story!

 

[doug293cz]

Biggest problem with the pot is that it's only 1/4 watt. Fan pulls more power than that, so not a good match. I'd go with a triac based voltage regulator circuit. A lamp dimmer should work. You can get short extension cords with in-line dimmers for not too much $$.

Brew on

 

[Codfishhead]

Sent the pics to my electrical eng buddy. This is NG. I think I have a dimmer switch in my outbuilding. I'll give that a shot later. He said a potentiometer would be best but a dimmer will work fine for the little motor in the fan.

Thx guys

Now it's time to go clean up those lovely leaves at my mother in laws. This is where I would add a puking avatar if I saw one.

Tonight I have a Tumbler Clone to wrack off. Hope to get this stir plate going to harvest n wash some yeast. Also have a brown ale that is almost ready for keg. going in another day or so followed by wracking off the Choc Porter I made last night.

Shooting for 7 beers brewed in 12 days. Lots of yeast to play with. Need to go by some canning jars today.

 

[HopinJim]

Yeah...for that fan, a dimmer switch would be the ideal choice. If you put that pot in the circuit, you would soon see the "magic smoke" come wafting out of it. BTW, I'm an EE.

 

[YeastMode]

If it is worth your time to return it, this would be the item that I used along with many others for applications similar to yours. Good luck.

http://www.radioshack.com/25-ohm-3-watt-rheostat/2710265.html

 

[Codfishhead]

Trying to hook up a double pull dimmer to the plug on my fan. There's 2 red wires on the dimmer. I hook one then both up and the fan hums n hardly moved both times.

Help please

 

[doug293cz]

What's the manufacturer and PN for that dimmer? Do you have any documentation on how it's supposed to be wired?

Brew on

 

[Codfishhead]

I have nothing.
Name on it "lutron"

 

[BlkWater_brewer]

A simple search of luton dimmer switch will answer your question??? But here: http://www.lutron.com/TechnicalDocumentLibrary/0301036A.pdf

BTW for the guy who said to add a potentiometer, thats what a dimmer switch is.

 

[doug293cz]

You can find data on Lutron dimmers here. Can't see all the stampings on the unit in the pic. Is there anything on it that looks like a part number?

Also, you should tie the ground wire from the dimmer into the cord grounds for safety.

Brew on

 

[doug293cz]

A simple search of luton dimmer switch will answer your question??? But here: http://www.lutron.com/TechnicalDocumentLibrary/0301036A.pdf

BTW for the guy who said to add a potentiometer, thats what a dimmer switch is.

Most modern dimmers are a potentiometer controlled triac circuit. The load current flows thru the triac, not the potentiometer. Much more efficient than a series potentiometer.

Brew on

 

[Codfishhead]

Hooked it up every which way. Hummed n hardly moved. Went n grabbed a single pull dimmer. Hooked it up n it won't go slow. Think the fan is just to powerful. Once it starts it's way to fast. 1" bar jumps around and flys off.


Think a small bar would stay?

 

[doug293cz]

I did some more googling on fan speed control and came across this short primer. Looks like an AC fan is a poor choice for a variable speed stir plate since the AC motors require more sophisticated speed controllers than DC motors. A simple light dimmer is unlikely to have the snubber circuitry needed to protect the fan motor from the inductive kickback spikes.

Brew on

 

[Codfishhead]

Found a pile of old PCs at work. 3 fans in each of the bigger ones. One old cell phone charger n no speed control. Works like a champ

http://youtu.be/ksGz1HZX4aI

 

[John53189]

Thats what i was going to suggest...test the 12v setup,or i was thinking the fan was toast. VFD's are another expensive option