# 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
8
0
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
13,518
3,386
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
105
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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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
8
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So why did they label it as a POT?

6. ### abhaymv Active Member

Aug 6, 2011
105
4
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.

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
3,879
1,396
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
12,403
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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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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.
Max.

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10. ### tracecom AAC Fanatic!

Apr 16, 2010
3,879
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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
2,402
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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
13,518
3,386
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
13,518
3,386
If the variable resistor is a two-terminal device, then no it cannot be used as a pot, which has three terminals.