Stir Plate Question? Fan pulses

Looked all around to find the answer and can't find it so I'm posting it here? Built and wired the stir plat everything works but my fan speed pulses. Fan speeds up and slows down. It creates a vortex and then goes away and cycles like that when its on. Material used transformer 120/12v dc, 12v 30 amp rocker switch, 25 ohm rheostat 3 w. Used brushless 12v dc fan. Whats causing the issue? Would this still work as a stir plate if it pulses like this creating vortex half the time?

I think your fan is shot. The cheaper ones don’t have ball bearings, they have a sleeve bearing. It wears, the shaft roughs up and gets tight, esp. when hot.

Do you have a voltmeter?

I’m guessing when you say ‘transformer’ you mean power supply. I’m not sure what a brushless motor would do with AC.

You can't transform dc volts. You need to add a rectifier or a diode in series of your 12v.

I used a power supply its 120v ac to 12v dc. I will try to upload a video tomorrow of my situation so you can see what's going on

Video with audio would be ideal, but just having some idea of the period of the pulses would give us a start...

Cheers!

Here's the video of what my stir plate is doing!

[ame]http://youtu.be/TUSKQrFMyWY[/ame]

fur_252 said:

Here's the video of what my stir plate is doing!

Video Link: http://youtu.be/TUSKQrFMyWY

Click to expand...

I'm leaning towards bad fan also.

I kinda dig it. Has that pulsing "Mad Scientist" vibe going on.