Trying To Make A Magnetic Stirrer - Help Needed Please

[Rob S]

I got some components together to make a magnetic stirrer and it's all looking good except for speed control for the PC fan.

The fan is off a PC and runs fast.

The power supply has 12V 1000mA output.

The LED dimmer is one off eBay that I've seen someone else use on this site or another one??



The problem is that the dimmer doesn't work. The fan is the same speed no matter the position of the LED dimmer.

It's a 4-wire fan and I found the two wires that make the fan go when connected straight to the power and cut the other two off. Hopefully I wasn't supposed to use one of these wires....I can't seem to get google much useful information about these fans wrt LED dimmer as speed controller.

I also have two different 3-wire fans (with the spare wire cut off) but from google the third wire is a tacho used by the computer as a check and balance to ensure that the fan is working to speed.

Any help would be a sensational as I want to put down my next beer in a couple of days.

Cheers,
Rob

 

[hoppinmad]

I had the exact same dimmer control and initially had the same problem. There was a thread I found which described in detail how to wire it so have a good search on here. The problem was pretty simple from memory like having the positives and negatives in the wrong terminals. Try a few different combinations of positive and negatives and it will eventually work.

 

[Camo1234]

I got some components together to make a magnetic stirrer and it's all looking good except for speed control for the PC fan.

The fan is off a PC and runs fast.

The power supply has 12V 1000mA output.

The LED dimmer is one off eBay that I've seen someone else use on this site or another one??

View attachment 53036

The problem is that the dimmer doesn't work. The fan is the same speed no matter the position of the LED dimmer.

It's a 4-wire fan and I found the two wires that make the fan go when connected straight to the power and cut the other two off. Hopefully I wasn't supposed to use one of these wires....I can't seem to get google much useful information about these fans wrt LED dimmer as speed controller.

I also have two different 3-wire fans (with the spare wire cut off) but from google the third wire is a tacho used by the computer as a check and balance to ensure that the fan is working to speed.

Any help would be a sensational as I want to put down my next beer in a couple of days.

Cheers,
Rob

Swap your + and - wires around on the speed controller.... I have no idea of electronic reasons but when I first wired mine up the speed controller didn't effect the speed but when I swapped the wires (ie Black and red from + to -) it worked well.


I may be completely off here but give it a go :icon_cheers:

 

[benno1973]

^ Mee too. Felt like an idiot, but swapping the wires around resolved the issue.

 

[Rob S]

Yep, did it and it worked like a charm. Thanks for your help you three.

 

[1974Alby]

what magnet is that in your pic? and where did you get it?

 

[Rob S]

Just a bar magnet with N on one side and S on the other. $1.20 from Leading Edge Electronics.

Just bought a square Sistema plastic lunchbox from Coles for it to sit in. It was sitting in a used plastic ice cream container which was working fine.

Total price under $25 (fan and power supply were foc).

 

[Camo1234]

Just a bar magnet with N on one side and S on the other. $1.20 from Leading Edge Electronics.

Just bought a square Sistema plastic lunchbox from Coles for it to sit in. It was sitting in a used plastic ice cream container which was working fine.

Total price under $25 (fan and power supply were foc).

So that type of magnet is working well? can you use varying sized stir bards in there? May take the pain out of trying to line up and space the rare earth magnets!