Resistance Voltage and Intensity in a small circuit

MrT123

Hi,

I've recently connected a potentiometer designed to slow down fan speed (its in its own case - its called Zalman Fanmate 2 and rated up to 6W, attaching a link below):
http://www.quietpc.com/gb-en-gbp/products/casefanaccessories/fanmate2

Potentiometer has burned.

The circuit consist of 2 fans connected in parallel-at leas it looks like they are parallel-otherwise they may only be grounded together but have separate sources (rated 12V, 0.4 A each). Fans are connected to the source on the motherboard of Xbox360(they are stock fans installed by Microsoft - no changes has been made).

Potentiometer was connected in series between the + and the fans.

Question is , why did it burned , and what Potentiometer should I use to make it work?

Also is it possible to perhaps use 2 same Potentiometers in Parallel or maybe to change fans from being connected Parallel to Serial in order to decrease their rotation speed.

Any formulas on how to calculate I,U and R for this scenario are welcomed.

Hope I didn't make it too messy, I can attach a drawing if necessary. Thx.

DublinDilbert

MrT123 wrote: »

Question is , why did it burned , and what Potentiometer should I use to make it work?

It burnt out cause you exceeded the maximum power dissipation of the potentiometer.

What type of motor are you trying to control the speed of?

MrT123

DublinDilbert wrote: »

It burnt out cause you exceeded the maximum power dissipation of the potentiometer.

What type of motor are you trying to control the speed of?

Thanks for the answer Dilbert. The motors are the ones on the picture below(like I said before there's two of them ):

FarmerGreen

The fans are rated at 12V 0.4A each
Power is VxI watts, 12x0.4=4.8W each
For two is 9.6W

The spec for the speed controller says
'Maximum allowable fan wattage 6W or lower'

You fried it!

You need two controllers, one for each fan, theyre only £3.

MrT123

Thats what I thought.

This time I want to use this fan controller:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=250628382845

Max power output of this fan controller is 12W, so I assume I could use only one. However now I'm very cautious and would like to install potentiometer that will handle both of the fans for continuous work. So I wonder if I can connect 2 fan controllers either parallel or in series (picture below has all 3 variants):

Question is should they go parallel or in series?

FarmerGreen

Split the fans.
Plug one fan into one controller, other fan into other controller.

DublinDilbert

There fixed it for ya....

MrT123

thanks guys,

I hope things won't catch in flame this time .

I also managed to burn an Arctic Cooling 12V 90mm fan while testing on random 9V power supply(this one goes independent from other two), so I'll order everything on eBay again and hopefully things will work .

Will post the results with some pics once finished.

Cheers,