potentiometers (pin1-pin2 soldered together)

[Orc General]

I picked up some rheostat type potentiometers for use in a project. I
notice that the middle connector is soldered together with one of the side
connector. As you know potentiometers have 3 connectors. I am wondering
what was the original intend of the person soldering two of the 3 pot
connectors together. I know if changes the resistance measured, but in what
way?

 

[John Popelish]

Orc General wrote:

I picked up some rheostat type potentiometers for use in a project. I
notice that the middle connector is soldered together with one of the side
connector. As you know potentiometers have 3 connectors. I am wondering
what was the original intend of the person soldering two of the 3 pot
connectors together. I know if changes the resistance measured, but in what
way?

If you are using the pot as a variable resistor (rheostat) and the
wiper makes perfect contact with the resistive element, then there is
no difference whether or not the wiper is also soldered to the unused
part of the resistor. But if the wiper skips over a bit of crud and
looses contact with the element, then the difference is that one goes
open circuit and the other just has a jump to full element resistance
at that spot.

 

[Spehro Pefhany]

On Thu, 19 May 2005 12:27:21 -0700, the renowned "Orc General"
<orc_general@hotmailNOSPEM.com> wrote:

I picked up some rheostat type potentiometers for use in a project. I
notice that the middle connector is soldered together with one of the side
connector. As you know potentiometers have 3 connectors. I am wondering
what was the original intend of the person soldering two of the 3 pot
connectors together. I know if changes the resistance measured, but in what
way?

It doesn't change the resistance measured by very much. It can improve
the apparent CRV a bit, so it's good practice to connect it that way.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[R Adsett]

In article <Q73je.3861$Wp.597749@news20.bellglobal.com>,
orc_general@hotmailNOSPEM.com says...

I picked up some rheostat type potentiometers for use in a project. I
notice that the middle connector is soldered together with one of the side
connector. As you know potentiometers have 3 connectors. I am wondering
what was the original intend of the person soldering two of the 3 pot
connectors together. I know if changes the resistance measured, but in what
way?

That's a 'standard' two wire pot. I see them a lot. Basically the wiper
and one end are tied together. The resistance across the paired leads
and the remaining single lead varies with angle, assuming a linear pot it
will vary linearly with angle. The sole advantage compared to leaving
the terminal unshorted is that is impossible for the end user (the one
who didn't short the two terminals together) to hook it up wrong. IE it
is polarity insensitive. It is otherwise identical to hooking up to the
wiper with one wire and the appropriate end with the other.

Hmm, now that I think about it, if the wiper goes open for some reason it
also limits the maximum resistance. I don't know if that's useful in any
application or not. It's not in the ones I know that use it.



Robert

 

[Rich Grise]

On Thu, 19 May 2005 12:27:21 -0700, Orc General wrote:

I picked up some rheostat type potentiometers for use in a project. I
notice that the middle connector is soldered together with one of the side
connector. As you know potentiometers have 3 connectors. I am wondering
what was the original intend of the person soldering two of the 3 pot
connectors together. I know if changes the resistance measured, but in what
way?

Um, you turn the knob one way and it increases, and you turn the knob
the other way, and it decreases?

Seriously, though, that's done to increase the reliability. If, for
some reason, the wiper fails to make good contact with the element,
then with pin 1 & 2 shorted together, the total resistance only jumps
to the max. resistance of the pot, rather than infinity.

Hope This Helps!
Rich