DIY Stir plate rheostat/pot question

[stever1000]

I am having trouble finding a rheostat/pot to use for my DIY stir plate. Many easy tutorials suggest a 3W 25 ohm rheostat. I have searched but there is so much information

As long as it is 3W or more, it will work right? i.e. if I get one rated for 5W?

And if I get one with a resistance more than 25ohm, it will have a wider range of slowing the fan down? Or is 25 the magic number?

I can only find 5W 25ohm for $10 or 5W 0-100ohm for 7$

The internet says RadioShack has the ideal one for only 2$ which is why I am confused I can't find a similar replacement for a similar price. I live in Canada and RadioShack doesn't exist anymore, which is making this project more difficult

Thanks!!

 

[d3track]

Any surplus stores near you? That's where I get mine here in the U.S.

 

[RM-MN]

You need a rheostat with at least a 3 watt rating, higher is better. You don't want to go much higher in resistance than the 25 ohm as it will be much harder to get the speed you want since the useable range will be compressed to one end of the rheostat's range of motion.

 

[SteelManCM]

If you're looking at spending close to $10 anyway, get a Pulse Width Modulator. Here's the one I use:

PWM on Amazon

The PWM will help with not burning out the rheo/pot

 

[Natdavis777]

I use a PC fan speed controller (rheostat) for my 3 stirplates and all work well.

 

[stever1000]

If you're looking at spending close to $10 anyway, get a Pulse Width Modulator. Here's the one I use:

PWM on Amazon

The PWM will help with not burning out the rheo/pot

From what I understand this method is a lot more complicated to wire.

 

[SteelManCM]

Not at all! Easier, even. No need to figure out which posts on the rheostat the wires are soldered to.

Two wires for power going in to the top terminal, two wires going to the fan in the bottom. Note that there are two PWMs in the picture.

Here's the full build: http://imperialhops.blogspot.mx/2015/04/dual-stir-plate.html

Easier still, if your fan has a 3-prong connector on it, you can use the Zalman fan mate and just simply plug the fan in to the controller.

I have that build here: http://imperialhops.blogspot.mx/2015/03/since-we-are-graduating-to-10-gallon.html

 

[stever1000]

Interesting! I will see if I can find one locally for a similar price to the rheostat/pot

Thanks!