Stir Plate Wiring Help - Fan Speed Not Working

[enthuzed]

All,

Putting together a stir plate from spare parts (like most everyone has done). I wanted to wire everything up before I soldered and put into my project box.

The fan is spinning no problem, but the fan speed controller does not seem to do anything at all. It is not your typical potentiometer with 3 connection points.


Do you see anything wrong? Or any suggestions to get the speed controller working properly?

Cheers!

 

[k_mcarthur]

Mine has the same problem, found out it was the 5 volt cell phone charger to blame. Tested it with a door bell transformer which is 12 volt and it kept throwing the bar, too much power I guess or not strong enough magnets. I use the 5v at full speed and it has worked fine for 20+ starters, even 2L lager starter. If it works don't mess with it.

 

[enthuzed]

True about if it spins... don't mess with it. I am using a 6V charger. Maybe the CPU fan controller has too much internal resistance to not even do anything?

 

[blefferd]

I have no clue about wiring stuff up, maybe someone that does will chim in, but could be wired wrong?

I had some issues wiring mine up but after a couple tries I got it right. It stirs the best with the power turned about a quater turn, once it gets started I can adjust the speed up but it usually throws the bar. At quater power it stirs a 1L starter just fine with no issues.

The biggest issue I ran into other than trying to wire it was getting the correct distance from the flask so it would stir correctly. It was either to close or to far away but finally got it sit correctly.

You might try mocking it up to see if it will stir liquid at max speed.

 

[k_mcarthur]

I have no clue about wiring stuff up, maybe someone that does will chim in, but could be wired wrong?

I had some issues wiring mine up but after a couple tries I got it right. It stirs the best with the power turned about a quater turn, once it gets started I can adjust the speed up but it usually throws the bar. At quater power it stirs a 1L starter just fine with no issues.

The biggest issue I ran into other than trying to wire it was getting the correct distance from the flask so it would stir correctly. It was either to close or to far away but finally got it sit correctly.

You might try mocking it up to see if it will stir liquid at max speed.

I used cabinet bumpers (clear rubber dots to keep doors from hitting wood on wood) on top of plate. Keeps the right distance, soft spot for expensive Pyrex flask, and a non skid addition.

 

[enthuzed]

Thanks for the ideas. I just wired it straight (AC/DC adapter to fan) and the stir bar spins perfectly with 1L. Goes good for about 1 min. Then the speed increases and it jumps off. The speed adjuster is definitely not working/wired correctly. I just ordered a real rheostat so maybe that will work for speed control.

 

[blefferd]

Any clue why the speed would increase after a min? I would think it would go a constant speed with constant/same amount power being supplied?

Did you try adjusting the distance between the fan and stir stick/flask?

 

[enthuzed]

The old CPU fan controller was junk (thank you china ebay)....

I went to radioshack bought a 25 ohm rheostat and a knob. Violah It works like a gem. Hooked everything up and it's now sitting pretty with a rocker on/off switch and speed controller.

Beware of chinese knock offs.... Should of went to radioshack to begin with

 

[blefferd]

Mine was built completly out of parts from Radio Shack except for the power converter, magnets and sitr bar. It rang in around $50, probably could have built it cheaper, if I had an old PC laying around. (I still dont see how people build them for less than $20!)

It was interesting building it, knowing nothing about electricty or wiring stuff up and the "How To's" on here where not really helpful when it came to wiring it all up. I ended up swapping the wires around till it worked. Then played with the distance between the fan and flask till it would stir my flask nicely. It works like a champ now!

 

[enthuzed]

I went ahead and drew up a schematic of the wiring that I used and works. I hope people will use this in the future Let me know if anyone has questions about wiring.

Prost!