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-   -   DIY Stir plate question (http://www.homebrewtalk.com/f51/diy-stir-plate-question-122322/)

gchunter 06-04-2009 03:34 AM

DIY Stir plate question
 
I started to make a stir plate following from a search on this forum (<http://www.homebrewtalk.com/f51/my-s...y-build-86252/). It looks like my fan might be bad out of an old computer I had. It was in the basement for about 3 months and the fan had been working. The fan I used had 3 wires red, black, and white. I tried hooking it up as shown for the 2 wire fan instructions and that didn't work. I also tried hooking it directly to the power source and then tried all of the possible combinations directly to the power source. Is there something I am missing or do I just have a bad fan? I have another old computer that I can get my hands on as well and get the magnet and fan out of but would appreciate any help.

The power source does work as it lights up the led light on the power switch to the stir plate.

BrewBeemer 06-04-2009 04:43 AM

You sure that you have voltage at the output of your power supply?
Lights on does not mean you have power out. The Red Black should be the fan leads. If hooked up backwards the fan will not run at all, reverse the polarity it should then run. Check with a volt meter the leads from your power supply as it is rare for a computer fan to take a dump.
The larger low rpm fan motors like 4" that draw higher currents of the 500 to 700 mA range will provide more torque running under a reduced voltage for your slower stir speeds. This is what you want.

gchunter 06-04-2009 12:53 PM

I am using a 12 volt cell phone charger that worked prior to cutting the cell phone charging end off. It is a 12 volt fan from the computer so it should be the same voltage. I had tried all combinations of connections for wiring and nothing worked to get the fan moving. I'll try testing the power cord.

The computer fan does not run constantly in a computer and only turns on when needed. Could there be a switch or delay that I have to overcome to get this fan to work?

Hang Glider 06-04-2009 03:45 PM

gchunter - any delay for the fan to work is thermostatically controlled elsewhere. If the fan is removed from the system, a simple red to red, black to black should work fine (assuming DC power, DC fan). if you've attached your magnet to the fan - try taking it off until the problem is solved. My magnet was too strong and interferring with the motor. I ended up separating the magnet from the motor by half an inch with spacers.

BrewBeemer 06-04-2009 08:29 PM

The Power Tower I took apart made by Sun had six 12 volt 720 mA 4" fans on it with a red, black plus two whites to a thermal probe a little 1/4 drop of epoxy looking thing on the fan in the airstream. Not only this if at above 5.5 volts and stall the fan after 4 seconds the thermal unit in the fan would kick off the power. A overload protection I believe. I was told these were pig motors with the amount of current they draw but this allows for more torque also especially when the voltage is lowered for speed control as in a stir.
I ordered a LM317 adjustable voltage powwer supply that can handle 1.5 amps thru ECROS Technology for $9.95 with a couple bucks shipping. It is a kit needing to be soldered together. That and a Radio Shack project box then im good to go. For a few minutes at the curbside I had six free fan motors.

gchunter 06-05-2009 03:25 AM

I have access to another fan and will try that one first. If that doesn't ork I think I will look into trouble shooting it further. I am just think it might be a quick easy fix but chances are I am wrong.


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