Grimsawyer said:
Hack job or not. Which route is the cheapest? Won't they both work exactly the same once the box is closed? turn on and dial up or down? Then if you get a voltage regulator sometimes you need a heat sink. It sounds like, to me(remember I'm not a electronics guy) to get the same result it'd double the price and be much more complicated than it needs to be. I'm not trying to flame anyone, at all. I'm not attacking anybody either. Just don't know alot about electronics beyond what i picked up in electronics class in high school 15 years ago. =) Sounds like a tuner vs. muscle car type of debate... each might have 500 horses and 700 foot pounds of torque but the muscle car seems easier to build than a computer driven highly modded 4 banger but in the end both go really, really fast.
I agree, once the box is closed it doesn't matter too much... But, I'm an electrical engineer, and I sort of cringe at the thought of using a potentiometer as a variable current limit for a motor, just because it's a hack job.
But the other half of the story is that a voltage regulator circuit is much more flexible - it will work the same whether you are using a 12v power supply, 15v, or whatever - and it will allow you to control any regular 12v computer fan, without needing to change component values around.
A potentiometer used as a fan speed control will perform differently depending on the power supply voltage you are using, and also on the particular fan you are using. If you pick a potentiometer that is too far from an ideal value for your PS/fan combo, the adjustment range won't be very good - you might have the fan go from fully on to fully stopped in just a fraction of the rotation range of the potentiometer, as happened to the original poster.
Also, since you mention price, based on prices at Digikey (a major online electronics retailer) a 3W potentiometer is about $3.50, and parts for a voltage regulator circuit are about $3-5. Of course, one requires more soldering than the other, but the price isn't much different - and besides, it's still a small part of the total cost of the stir plate in either case.
Not to say that nobody should use the simple potentiometer method for stir plates, all I'm saying is that as an engineer, I simply would not personally recommend it to someone - it's just not good engineering practice. But if it works for you and you're happy with it, great.
![Mug :mug: :mug:](https://cdn.homebrewtalk.com/smilies/sdrinking-100-154.gif)