Pots!

Lostcause · 14th December 2006, 02:13 PM

Simple question for the EE's out there......
If you tie the wiper and ground of a pot together does it then give you the parallel resistance?
i.e. 500K pot becomes 250K when fully open?

cliffforrest · 14th December 2006, 03:18 PM

You don't need to be an EE to answer that!

Draw the symbol for a pot with the wiper at the "top." Join the wiper to the top connection.

Now in what way can there be anything other than the full resistance between top and bottom?

Now move the wiper to 1/2 way down. what is the resistance?

Wiper at the bottom - resistance?

YOU can work these things out by common sense.

Nordic · 14th December 2006, 04:42 PM

in short it becomes a variable resistor as oposed to a variable voltage splitter...

Lostcause · 14th December 2006, 06:12 PM

OK, OK, I thought it a valid question.....

When you have two resistors in parallel there is a sum between them...
When you look at the wiper it has a resistance and when you look at the ground it has a resistance...not in series but effectively in parallel...not such a silly question but thanks for putting me right anyway.

cliffforrest · 14th December 2006, 08:46 PM

It was not meant as a put-down but as an encouragement to explore and use your common sense!

Many many things in engineering do not need specialised knowledge or education to understand at a first level, but a bit of thought and experiment.

head_spaz · 14th December 2006, 11:40 PM

Quote:

If you tie the wiper and ground of a pot together does it then give you the parallel resistance?

In the example you give, the ground-legged-side of the "voltage divider" will have ground on each / both ends.
Is there a differential?
How many ohms does it measure if both ends are connected to the same ground?

14th December 2006, 02:13 PM	#1
Lostcause diyAudio Member Join Date: Aug 2005 Location: NW UK	Pots! Simple question for the EE's out there...... If you tie the wiper and ground of a pot together does it then give you the parallel resistance? i.e. 500K pot becomes 250K when fully open?

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14th December 2006, 03:18 PM	#2
cliffforrest diyAudio Member Join Date: Sep 2004 Location: South Coast, UK	You don't need to be an EE to answer that! Draw the symbol for a pot with the wiper at the "top." Join the wiper to the top connection. Now in what way can there be anything other than the full resistance between top and bottom? Now move the wiper to 1/2 way down. what is the resistance? Wiper at the bottom - resistance? YOU can work these things out by common sense.

14th December 2006, 04:42 PM	#3
Nordic diyAudio Member Join Date: Sep 2005	in short it becomes a variable resistor as oposed to a variable voltage splitter...

14th December 2006, 06:12 PM	#4
Lostcause diyAudio Member Join Date: Aug 2005 Location: NW UK	OK, OK, I thought it a valid question..... When you have two resistors in parallel there is a sum between them... When you look at the wiper it has a resistance and when you look at the ground it has a resistance...not in series but effectively in parallel...not such a silly question but thanks for putting me right anyway.

14th December 2006, 08:46 PM	#5
cliffforrest diyAudio Member Join Date: Sep 2004 Location: South Coast, UK	It was not meant as a put-down but as an encouragement to explore and use your common sense! Many many things in engineering do not need specialised knowledge or education to understand at a first level, but a bit of thought and experiment.