Struggling with a DIY stirplate

I've been trying to put together a stirplate for a while now but I can't get the wiring right. I have a link of my wiring at the end of this post, but to be more descriptive:

I have the fan plugged into the rheostat
The rheostats red wire is connected to the white striped AC wire
The rheostats black wire is connected to the other black AC wire
When I plug in the AC adapter, nothing happens

This seems like it should be simple, so what am I doing wrong?

http://imgur.com/a/ajrSf

Your power supply is only 9V and the fan is looking for 12V. That could be a potential issue, I think.

I'm pretty sure that would just make it spin slower. I think that is how rheostats work as well, they control the voltage going to the fan.

Havacore said:

I'm pretty sure that would just make it spin slower. I think that is how rheostats work as well, they control the voltage going to the fan.

Click to expand...

That's somewhat correct, but at a certain point the fan won't be able to spin at all. Usually that happens somewhere around 5V though, I've never seen one not able to spin from 9V. Unless your rheostat is adding too much resistance? It's difficult to diagnose something like this without even more details. It could be any number of things, even something as simple as connecting the fan backwards.

Wire the fan directly to the power adapter. If it runs, you know your power supply and polarity are correct. Cut the rheostat into one of the supply lines, make sure to wire it correctly, and if it doesn't work you've likely got a rheostat with too much resistance for your application.

Havacore said:

.....I have the fan plugged into the rheostat
The rheostats red wire is connected to the white striped AC wire
The rheostats black wire is connected to the other black AC wire
When I plug in the AC adapter, nothing happens

This seems like it should be simple, so what am I doing wrong?

http://imgur.com/a/ajrSf

Click to expand...

Is that block box, the "rheostat" or is that part of the fan? Can you provide some information on it?

BTW, the voltage provided by the AC adapter is 9V DC. 9 volts should spin your fan. I'm just not sure what that black box is doing?

The black box looks like a PC fan controller to me. You might have to go with 12v just to fire that thing up. There could be some extra components etc. in there that might be looking for 12v. As has been suggested, try directly wiring the fan, then you know where your problem is.

Ok, so I cut the connector off of the fan, took a guess as to which wire was neutral and SUCCESS. It spins at full force, without any control. Is there any way now for me to control the voltage without using the rheostat? Is it entirely necessary?

Do you have a rheostat?

Honestly if the black box is a fan speed controller, as its suspected(with Low/Medium/High) i wouldnt even bother with a Rheostat...

I didnt even bother with one, i just wired a resistor in line with the power cable to pull it down to like 8.5V.

No need for the fancy custom speeds IMO, it needs to spin slow enough to not fling the stir bar, no more no less.
Just plug and unplug it from the wall when i need to turn it off lol.

Have you tested if with the 9V power supply hooked up directly that it will or wont fling the stir bar? You have to remember your gluing on a relatively heavy metal to it(compared to the plastic fan itself), which will slow it down even more.

Honestly with a 9V power supply i bet it would just work plugged directly into the wall with no rheostat.