Wire a potentiomete in to a circuit

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Discussion Overview

The discussion revolves around wiring a potentiometer into a circuit for a magnetic stirrer, specifically focusing on voltage regulation. Participants explore various methods to achieve the desired voltage output for optimal performance of a motor, including the use of voltage regulators and the challenges faced in achieving specific voltage levels.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on wiring a potentiometer to regulate voltage for a magnetic stirrer.
  • Another suggests using a voltage regulator, specifically the LM317, in conjunction with a potentiometer for adjustable voltage control.
  • A participant expresses frustration with the difficulty of achieving a specific voltage (5.6 volts) for optimal motor performance.
  • Discussion includes the motor's specifications, rated at 12V and 0.15A, and the potential use of a 12V wall adapter instead of a 9V battery.
  • Concerns are raised about the suitability of the LM317 voltage regulator for high current applications, particularly for a 320A alternator setup.
  • Participants discuss the need for larger voltage regulators and alternative methods, such as using multiple parallel power BJTs for high current regulation.
  • There is mention of using pulse width modulation (PWM) to control the field coil current in alternators, with varying opinions on its application in automotive alternators.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of the LM317 for high current applications, with some suggesting alternative approaches. The discussion remains unresolved regarding the best method for voltage regulation in high power scenarios.

Contextual Notes

Limitations include the lack of consensus on the appropriate voltage regulator for high current applications and the specific requirements for achieving desired voltage outputs in different setups.

Who May Find This Useful

Individuals interested in circuit design, voltage regulation, and those working with motors and alternators in experimental or practical applications may find this discussion relevant.

Squall
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i need to know how to wire a potentiomete into a circuit. More specifically i am making a meagnetic stirrer and need to regulate voltage how would i wire the pot into the circuit.
 
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To regulate voltage (if there is more than a few milliAmps involved), you should use a voltage regulator for the power element, and the potentiometer as the voltage control. Check out the datasheet for the LM317 adjustable positive voltage regulator -- it describes how to combine it with a potentiomenter to make an adjustable voltage regulator.
 
thanks but i figured it out through trial and error
 
Squall said:
thanks but i figured it out through trial and error
Did any of the errors make smoke or fire?
 
Of course; it doesn't really count as an error otherwise. :rolleyes:
 
no they didnt i used a 9 volt battery no sparks no nothing until i got the right circuit and the motor turned on. But i am disapointed at how hard it is to get the right voltage i need a very specific voltage to achieve a maximum vortex which is around 5.6 volts. I've only been able to hit the sweet spot a few times in the last hour.
 
Squall said:
But i am disapointed at how hard it is to get the right voltage i need a very specific voltage to achieve a maximum vortex which is around 5.6 volts. I've only been able to hit the sweet spot a few times in the last hour.
That's one of the reasons I suggested using an adjustable voltage regulator -- to get maximum power to the load. What voltage and current are the motor rated for? How long do you need to run it off of the 9V battery?
 
its rated at 12v .15A. So how those this voltage regulator work exactly.
 
Squall said:
its rated at 12v .15A. So how those this voltage regulator work exactly.
Then the motor will only run well at 12V. Can you use a 12Vdc wall adapter instead of the 9V battery?

Here is some background info about voltage regulators. They are used to control an output voltate when supplied with a higher input voltage. To make a stable 12Vdc output, you would typically use a low-cost regulator that takes as an input something >= 15V, or a slightly more expensive "low dropout" regulator that requires an input voltage of something like >= 13V.

http://en.wikipedia.org/wiki/Voltage_regulator
 
  • #10
I tried to build the same voltage regulator, but mine smoked real quick twice... I believe that the LM317 is not the recomended voltage regulator for me, since I have such a large alternator!
I was mainly trying to control the voltage of my 320Amp alternator, that is externally rectified running to a series of 8V batteries to gain up to 20VDC for 5-10 second increments...

I followed the easy shematics for the LM317 voltage regulator, and I think that there is too much voltage input that is causing the LM317 to blow... Is there a larger voltage regulator that will handle this type of voltage?

Seems like there would be...

Any help and info is appreciated

Thanks
 
  • #11
xhunter911 said:
I tried to build the same voltage regulator, but mine smoked real quick twice... I believe that the LM317 is not the recomended voltage regulator for me, since I have such a large alternator!
I was mainly trying to control the voltage of my 320Amp alternator, that is externally rectified running to a series of 8V batteries to gain up to 20VDC for 5-10 second increments...

I followed the easy shematics for the LM317 voltage regulator, and I think that there is too much voltage input that is causing the LM317 to blow... Is there a larger voltage regulator that will handle this type of voltage?

Seems like there would be...

Any help and info is appreciated

Thanks
Whew, I thought I was in the Twilight Zone there for a couple seconds, hunter. Are you sure you popped into the correct thread? In your other thread about voltage regulators:

https://www.physicsforums.com/showthread.php?t=139163

I thought you were building the discrete parallel BJT regulator to handle your high power requirements. An LM317 is a regulator for a couple amps, not 320A.
 
  • #12
what do you suggest for a regulator from the input side of a 320 amp alternator?

I tried the LM317 and smoked 2 of them...

Please help, I'm banging my head...
lol
 
  • #13
Have you tried the multiple parallel power BJT approach that I brought up in the other thread? You're going to need some honking big transistors (and lots of them) for a 320A regulator.
 
  • #14
berkeman said:
Have you tried the multiple parallel power BJT approach that I brought up in the other thread? You're going to need some honking big transistors (and lots of them) for a 320A regulator.

Hello Berkeman

Im going to take a picture of my current voltage regulator so you can see what I am trying to re-build...
I will post it in my initial thread...

Thanks
 
  • #15
xhunter911 said:
what do you suggest for a regulator from the input side of a 320 amp alternator?

I tried the LM317 and smoked 2 of them...

Please help, I'm banging my head...
lol
For an altenator what you want to regulate is the current going to the field coil. Not the rectified output.
Note that even the field coil will draw much more than an LM317 can provide.
 
  • #16
Also, the field coil (which is actually the rotor) has the current varied in it by pulse width modulation. The average current in it is maintained at a given level in order to maintain the desired output voltage under a given load.
 
  • #17
Averagesupernova said:
Also, the field coil (which is actually the rotor) has the current varied in it by pulse width modulation. The average current in it is maintained at a given level in order to maintain the desired output voltage under a given load.
I've never actually seen PWM used in an Auto alternator.
It's certainly a viable option though.
 
  • #18
I don't think ANY of them can do it without PWM. The field current is too high to do it any other way.
 
  • #19
Averagesupernova said:
I don't think ANY of them can do it without PWM. The field current is too high to do it any other way.
This circuit is representative of what I have seen used.

http://www.1stconnect.com/anozira/SiteTops/energy/Alternator/alt_06_1.gif
 
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