Make a Magnetic Stirrer: Fix Flea Spinning Problem

  • Thread starter Squall
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In summary, using a pot or rheostat to vary the resistance between the fan and the load will control the current and thus the speed of the fan.
  • #1
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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  • #2
Just a guess, can you reduce the speed of your driving fan?
 
  • #3
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.
 
  • #4
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.
 
  • #5
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.
 
  • #6
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?)
 
  • #7
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.
 
  • #8
Thanks, Integral. That will come in handy.
 
  • #9
Thank you Integral that's a lot easier than trial and error.
 
  • #10
Just wire it up works great Thanks a lot
 

1. How do I fix the flea spinning problem on my magnetic stirrer?

To fix the flea spinning problem on your magnetic stirrer, the first step is to check the alignment of the stir bar. Make sure that it is centered on the magnetic field and not touching the sides of the container. If the stir bar is still spinning, try adjusting the speed and strength of the magnetic field. If the problem persists, it may be an issue with the magnetic stirrer itself and it may need to be repaired or replaced.

2. What causes the flea spinning problem on a magnetic stirrer?

The flea spinning problem on a magnetic stirrer is typically caused by an imbalance in the magnetic field. This can be due to an uneven surface or container, an incorrectly positioned stir bar, or a malfunction in the magnetic stirrer itself. It is important to troubleshoot and identify the root cause in order to effectively fix the problem.

3. Can I use any type of container with a magnetic stirrer?

While most containers can be used with a magnetic stirrer, it is important to ensure that the container is made of a material that is compatible with the magnetic field. Glass, plastic, and stainless steel containers are commonly used with magnetic stirrers. It is also important to make sure that the container is flat and level in order to prevent the stir bar from spinning out of control.

4. How do I determine the appropriate speed and strength for my magnetic stirrer?

The speed and strength of a magnetic stirrer depend on various factors such as the viscosity of the liquid being stirred, the size and shape of the container, and the type of stir bar being used. It is best to start with a low speed and gradually increase it until the desired mixing is achieved. As for the strength, it should be adjusted so that the stir bar is spinning consistently without jumping out of the liquid.

5. Can I make my own magnetic stirrer?

Yes, it is possible to make your own magnetic stirrer using common household materials. However, it is important to note that homemade magnetic stirrers may not be as efficient or reliable as commercially available ones. It is also important to take necessary safety precautions when making and using a homemade magnetic stirrer.

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