Potentiometer (Hobby project)

Discussion in 'The Projects Forum' started by Brandon$B, Dec 14, 2013.

  1. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
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    Hi I have quick question about potententiometers.

    In this circuit:

    http://www.circuitstoday.com/light-activated-switch-circuit

    R1 is a Potentionmeter(POT)

    I'm using this specific POT:

    http://www.jameco.com/1/1/28515-rv16af-10-20r1-b54-potentiometer-50k-rv16a-10-20r1-b50k-linear.html

    I fully understand the purpose and operation of this device but I am baffled by what to do with the pins do I join pin 2 to pin 1 or 3? or what?

    Thank you for responding to my question your help is sincerely appreciated.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    You connect pin 2 to either pin 1 or pin 3 depending upon whether you want the resistance to increase or decrease when turning in a clockwise direction. You link gave me an error so I don't don't which way does what, but you can determine that by looking at the pot. It normally shows which way the wiper moves according to rotation direction.
     
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  3. abhaymv

    Active Member

    Aug 6, 2011
    104
    4
    If by 'join' you mean shorting the pins, no, you do not do that. That would defeat the purpose of the pot. The pot acts as a voltage divider.
    Refer to the figure. This represents a particular position of a 10k potentiometer. The middle pin, Pin 2, is used to divide the overall resistance of the pot (that is, resistance between pins 1 and 3) to two parts. Here R12 is 6k and R23 is 4k. Total resistance R13 = 10k.

    Adjusting the cylindrical knob will help you vary R12 and R23 so that they form different divisions of R13.
     
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  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Technically when used in that application it should be labeled VR variable resistor. ;)
    Max.
     
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  5. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
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    So why did they label it as a POT?
     
  6. abhaymv

    Active Member

    Aug 6, 2011
    104
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    I assume that's because the component is more commonly known in the market as a pot. As a hobby circuit rather than a professional one, its likely to give names that are readily identifiable in the market.

    Atleast that's what I think. :D

    But yes, that application works as a variable resistor, not as a potential divider. The technically correct name would be variable resistor.
     
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  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    A pot can be configured as a variable resistor (as in the circuit you posted) or as a voltage divider (as show in post #3.) In the circuit you posted, the correct answer is the one you got from crutschow.

    In my opinion, it's still a potentiometer regardless of how it's used.
     
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  8. wayneh

    Expert

    Sep 9, 2010
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    I tend to agree. Even if you use it as a doorstop, it's still a pot. One function of a pot is to act as a variable resistor.
     
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  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Probably for detailed definition, it is a potentiometer configured as a variable resistor, because it is not being utilized in the strict definition of a potentiometer. :cool:
    Max.
     
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  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    At any rate, I realize that my practice of identifying all potentiometers on my schematic drawings as VR1, VR2, etc., is wrong.
     
  11. BillB3857

    Senior Member

    Feb 28, 2009
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    So could one say that a potentiometer can be configured as a variable resistor but a variable resistor cannot be configured as a potentiometer? Now I'm confused!
     
  12. crutschow

    Expert

    Mar 14, 2008
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    Not necessarily. I agree with weyneh. A potentiometer (device) is a resistor with a variable wiper on the resistive element. It may be configured as a two-terminal variable resistor or a 3-terminal voltage divider but the device is still a pot, which can be configured different ways.

    Sometimes a transistor has the collector connected to the base and is used as a diode, but you don't call it a diode (actually makes a rather ideal diode). It's still a transistor.
     
  13. crutschow

    Expert

    Mar 14, 2008
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    If the variable resistor is a two-terminal device, then no it cannot be used as a pot, which has three terminals.
     
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