Make a Magnetic Stirrer: Fix Flea Spinning Problem

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Discussion Overview

The discussion revolves around the construction and troubleshooting of a magnetic stirrer made from a PC fan and magnets. Participants share their experiences with the device, specifically addressing issues related to the stirring mechanism and wiring components like potentiometers.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant reports that their magnetic stirrer does not function properly, with the flea switching directions and making noise instead of spinning continuously.
  • Another participant suggests reducing the speed of the driving fan as a potential solution.
  • A different participant proposes using a spacer between the primary magnet and the flea to improve performance.
  • One participant expresses uncertainty about wiring a potentiometer and seeks clarification on its function and connections.
  • Several participants provide explanations on how to wire the potentiometer, detailing the connections for both potentiometer and rheostat configurations.
  • Participants express appreciation for the wiring guidance, indicating that it simplifies their understanding and implementation.

Areas of Agreement / Disagreement

There is no consensus on the best solution for the stirring issue, as multiple suggestions are offered, including reducing fan speed and using a spacer. The wiring of the potentiometer is discussed with varying levels of understanding, but no definitive agreement is reached on the best approach.

Contextual Notes

Participants' suggestions depend on assumptions about the specific setup and components used, which may not be universally applicable. There are unresolved details regarding the optimal configuration for the magnetic stirrer and the potentiometer wiring.

Squall
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Hi i am trying to make a magnetic stirrer. I have seen tutorials on how to make a magnetic stirrer from a pc fan and magnets. i have actually constructed such a device, but the results I got were less than satisfactory. My problem is that the flea used to stir the solution doesn't want to spin. For some reason it keeps switching directions and makes a whole lot of noise, but doesn't spin continuously. Does anyone have any suggestions on how to fix the problem or maybe a whole new design.
 
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Just a guess, can you reduce the speed of your driving fan?
 
Squall said:
Hi i am trying to make a magnetic stirrer. I have seen tutorials on how to make a magnetic stirrer from a pc fan and magnets. i have actually constructed such a device, but the results I got were less than satisfactory. My problem is that the flea used to stir the solution doesn't want to spin. For some reason it keeps switching directions and makes a whole lot of noise, but doesn't spin continuously. Does anyone have any suggestions on how to fix the problem or maybe a whole new design.

Sometimes a spacer between the primary magnet and the flea will help. About 1/8" more should do it.
 
I have a potentiometer but I don't exactly know how to wire it. I remember messing with it a few months ago but i hooked it up by trial and error. It has three prongs they're not labeled. If some one could explain how it works i will appreciate it.
 
The outer 2 pins are the ends of a resistor. The middle pin is a wiper which touches the middle of the resistor. With the knob at the extreme right it is near the right pin and so there is minimal resistance between the right pin and the centre. As you turn the knob to the left the esistance between the middle and right pin increases and the resistance to the left pin decreases. The resistance between the left and right pin is constant.
Simply connect one of the outer pins to the the power supply, the middle one to the fan and the other side of the fan back to the other side of the power supply.
 
I've never known how to use one of those bloody things either; I'd only used straight rheostats. Does the ground side of the fan connect to the 3rd pin of the pot? (Or, more accurately, are they both connected to the same side of the power supply?)
 
2 ways to wire a pot:

1. As a potentiometer, connect both ends of the pot to the power supply, then one side of the PS and the center tap to the load. As you move the wiper you will "select" a voltage (potential) from the pot, thus the name.

2. As a rheostat, one side of the PS to an end of the pot, the other side to the load, center tap to the load. Note that one side of the pot is floating it is not connected to anything. With this arrangement you are varying the resistance in the circuit therefore controlling the current.
 
Thanks, Integral. That will come in handy.
 
Thank you Integral that's a lot easier than trial and error.
 
  • #10
Just wire it up works great Thanks a lot
 

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