slowing down a stir plate

[ChrisS]

So I too am building a stir plate from old parts lying around the house and one of those parts is an old tyco ho scalre train power pack. (not my image, but same product)

If I barely turn it on the fan is zooming. I thought there was another person using the same power pack but a few searches didn't turn up anything so any advice on slowing it down would be appreciated.

Thanks.

 

[Reno Homebrewer]

The speed control is basically a potentiometer, so if you go to Radio Shack, pick up a 5W potentiometer and put it in series with one side of your output, you should be able to control your speeds.

 

[ChrisS]

is this potentiometer similar to the fan control in the picture? Do they both work the same or perform the same function?

 

[Reno Homebrewer]

They are the same thing, but that one has a pretty housing. Basically, a potentiometer is a resistor that you can change the resistance of. For example, a 100kΩ potentiometer can be adjusted from no resistance to 100kΩ of resistance.

 

[wood7588]

When making my stir plate I found that starting with a low speed fan helped a lot. I had a stealth fan that had a max RPM rating of around 1300 (a little faster than real stir plates). I bought a 1M potentiometer for a couple of bucks at an electronics store. Hooked it all directly to a 12VDC power supply and got a terrific range of speed.