inverse log potetiometers ?

[Oyek]

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.


Oye

 

[Jamie]

Oyek wrote:

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.


Oye
If you need this for positioning something, mount an audio taper with

an offset gear and use the gear as your shaft drive.
just get your self 2 1/4" through hole gears. drill 2 holes to apart
from each other spaced correctly so that the gears will meet up.
use another pot as the shaft for the offset drive ...
etc...

we needed something like this one before how ever, what we did was
use a linear pot and mounted a small light weight disc to it in the center..
then we connected the device off to one side of the disc. when the
disc moves via the device arm you do not get a linear action. It gets
converted to a mechanical non linear effect.

You can use an opposing shaft with an offset Disc to get the non
linear action you're looking for. You just need to do some mechanical
math.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

[Eeyore]

Oyek wrote:

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.

They are very difficult to obtain. Pro-audio equipment is the only sector I know
that regularly uses them.

If you want a value other than 10k or 100k I'd look for another solution ! Your
best bet is likely to be an Alps part btw. Mouser or Digikey may well have them
bit I'll leave it to you to look. What you want is a 'C' taper. Or even Alps's
'RD' taper if they have it.

Graham

 

[Michael Black]

Eeyore (rabbitsfriendsandrelations@hotmail.com) writes:

Oyek wrote:

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.

They are very difficult to obtain. Pro-audio equipment is the only sector I know
that regularly uses them.

But you can get the effect of a log potentiometer with the proper value

resistor from the arm to one of the fixed ends of the pot. It's been
written up lots of times, and I recall something in "Electronics" about
using an op-amp for an improved implementation of it.

If it gives satisfactory results, then the inverse effect can be done
with putting the resistor to the other end of the pot.

Michael

 

[Eeyore]

Michael Black wrote:

Eeyore (rabbitsfriendsandrelations@hotmail.com) writes:
Oyek wrote:

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.

They are very difficult to obtain. Pro-audio equipment is the only sector I know
that regularly uses them.

But you can get the effect of a log potentiometer with the proper value
resistor from the arm to one of the fixed ends of the pot. It's been
written up lots of times, and I recall something in "Electronics" about
using an op-amp for an improved implementation of it.

If it gives satisfactory results, then the inverse effect can be done
with putting the resistor to the other end of the pot.

Yes I know, but in audio, both applications that regularly require 'antilog' pots
aren't actually voltage dividers, so it doesn't help.

Graham

 

[Salmon Egg]

Isn't inverse log the same as exponential?

Bill

 

[Eeyore]

Salmon Egg wrote:

Isn't inverse log the same as exponential?

In what was is that supposed to help ?

Funnily enough it's the classic 'log pot' that actually has an exponential style
law.

Graham

 

[Oyek]

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.


Oyek

Eeyore wrote:

Michael Black wrote:

Eeyore (rabbitsfriendsandrelations@hotmail.com) writes:
Oyek wrote:

Is there any inverse log/audio potentiometers in the market (mouser or
digikey ?) ?
I need potentiometers which resistor values decaying fast from bigger to
small values when they turn clockwise.I can use regular audio
potentiometers but unfortunately to get this effect I have to turn them
CCW.Thanks for your help.
They are very difficult to obtain. Pro-audio equipment is the only sector I know
that regularly uses them.

But you can get the effect of a log potentiometer with the proper value
resistor from the arm to one of the fixed ends of the pot. It's been
written up lots of times, and I recall something in "Electronics" about
using an op-amp for an improved implementation of it.

If it gives satisfactory results, then the inverse effect can be done
with putting the resistor to the other end of the pot.

Yes I know, but in audio, both applications that regularly require 'antilog' pots
aren't actually voltage dividers, so it doesn't help.

Graham

 

[Eeyore]

Oyek wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

You found a supplier OK then ? Do you have a link, it might be useful for future
reference.

Graham

 

[Oyek]

Here is the link I am looking for :
http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Potentiometer/InsulatedShaft/RK12L12/RK12L12.PDF

or you might go to their main website:
http://www.alps.com


Oye



Eeyore wrote:

Oyek wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

You found a supplier OK then ? Do you have a link, it might be useful for future
reference.

Graham

 

[Peter Dettmann]

On Sun, 29 Jul 2007 20:00:16 -0700, Oyek <wisnuardi@aol.com> wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.
Oyek

I first thought that there was something badly wrong but on checking I
find that taper designation has been changed. As I was aware the C
taper is the normal log taper, but it seems that a log taper is now an
A taper. Originally in my radio repair era, the A taper was the
linear pot. So all I can say, is to be wary of the taper
designation, and check that it is the style you really intend.
See also http://sound.westhost.com/pots.htm#taper

Peter Dettmann

 

[Eeyore]

Oyek wrote:

Eeyore wrote:
Oyek wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

You found a supplier OK then ? Do you have a link, it might be useful for future
reference.

Here is the link I am looking for :
http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Potentiometer/InsulatedShaft/RK12L12/RK12L12.PDF

But did you find a stockist ? That's my point.

I know very well Alps have this item in their catalogue (that's why I suggested them), but it is not
widely stocked. Usually it is only made to special order.

or you might go to their main website:
http://www.alps.com

Yes I know who Alps are thank you. You may recall I suggested them. Taiwan Alpha is the other company
who may be useful.

Graham

 

[Eeyore]

Peter Dettmann wrote:Oyek <wisnuardi@aol.com> wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

I first thought that there was something badly wrong but on checking I
find that taper designation has been changed. As I was aware the C
taper is the normal log taper, but it seems that a log taper is now an
A taper. Originally in my radio repair era, the A taper was the
linear pot. So all I can say, is to be wary of the taper
designation, and check that it is the style you really intend.
See also http://sound.westhost.com/pots.htm#taper

The C taper was *never* the normal audio log (volume control) taper in my (very
long) experience.

There has been a difference between the designations used for linear and log
between European and Japanese (and other Asian) suppliers though.

A = 'log' - audio volume control taper (JIS) Japan Industry Standard BUT
LINEAR EUROPEAN STANDARD.

B = linear (JIS) but audio taper for European suppliers.

C = 'reverse log' always.

Graham

 

[Lostgallifreyan]

Peter Dettmann <peter@aardvark.net.au> wrote in
news:913ra3dmomg6ps31ppe6d20mtsa3dsh4p6@4ax.com:

See also http://sound.westhost.com/pots.htm#taper

Thankyou. Extremely useful article to link to. The rest looks set to occupy
a lot of my time too.

 

[Peter Dettmann]

On Mon, 30 Jul 2007 11:46:42 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Peter Dettmann wrote:Oyek <wisnuardi@aol.com> wrote:


Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

I first thought that there was something badly wrong but on checking I
find that taper designation has been changed. As I was aware the C
taper is the normal log taper, but it seems that a log taper is now an
A taper. Originally in my radio repair era, the A taper was the
linear pot. So all I can say, is to be wary of the taper
designation, and check that it is the style you really intend.
See also http://sound.westhost.com/pots.htm#taper

The C taper was *never* the normal audio log (volume control) taper in my (very
long) experience.

There has been a difference between the designations used for linear and log
between European and Japanese (and other Asian) suppliers though.

A = 'log' - audio volume control taper (JIS) Japan Industry Standard BUT
LINEAR EUROPEAN STANDARD.

B = linear (JIS) but audio taper for European suppliers.

C = 'reverse log' always.

Graham

That is interesting Graham, as I had (from the 1950's) always found
the C designation to be the audio taper used in radio and amplifiers.
You have noted some of the less important areas like European, and
Asian, but in the center of the universe (Australia) we seem to have
our own 'standard'.
From the 1992 Dick Smith catalogue, the following are stated:
A = Linear
B = Logarithmic
C = Logarithmic
E = Anti-Log
J = Linear

On looking through my junk box, all the C's all measure as log, and
all the A's are linear. Another designation I found was W which is
a Wire Wound pot.

I can understand now that pots marked 'Log' or 'Lin' are a much safer
method.

Peter Dettmann

 

[Eeyore]

Peter Dettmann wrote:

Eeyore wrote:
Peter Dettmann wrote:Oyek <wisnuardi@aol.com> wrote:

Thank you !. yes, Alp have taper C.I never know that taper C is inverse
log pot.

I first thought that there was something badly wrong but on checking I
find that taper designation has been changed. As I was aware the C
taper is the normal log taper, but it seems that a log taper is now an
A taper. Originally in my radio repair era, the A taper was the
linear pot. So all I can say, is to be wary of the taper
designation, and check that it is the style you really intend.
See also http://sound.westhost.com/pots.htm#taper

The C taper was *never* the normal audio log (volume control) taper in my (very
long) experience.

There has been a difference between the designations used for linear and log
between European and Japanese (and other Asian) suppliers though.

A = 'log' - audio volume control taper (JIS) Japan Industry Standard BUT
LINEAR EUROPEAN STANDARD.

B = linear (JIS) but audio taper for European suppliers.

C = 'reverse log' always.


That is interesting Graham, as I had (from the 1950's) always found
the C designation to be the audio taper used in radio and amplifiers.
You have noted some of the less important areas like European, and
Asian, but in the center of the universe (Australia) we seem to have
our own 'standard'.
From the 1992 Dick Smith catalogue, the following are stated:
A = Linear
B = Logarithmic
C = Logarithmic
E = Anti-Log
J = Linear

Dick Smith is wrong.

On looking through my junk box, all the C's all measure as log, and
all the A's are linear. Another designation I found was W which is
a Wire Wound pot.

*JUNK BOX* i.e. nothing modern of course.

I can understand now that pots marked 'Log' or 'Lin' are a much safer
method.

You're unlikely to find pots marked log or lin any more in my considerable
experience..

Graham

 

[Peter Dettmann]

On Wed, 01 Aug 2007 19:18:40 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

From the 1992 Dick Smith catalogue, the following are stated:
A = Linear
B = Logarithmic
C = Logarithmic
E = Anti-Log
J = Linear

Dick Smith is wrong.

In your realm he may not be right, but he is certainly not wrong.

On looking through my junk box, all the C's all measure as log, and
all the A's are linear. Another designation I found was W which is
a Wire Wound pot.

*JUNK BOX* i.e. nothing modern of course.

You have to read the whole thing, and forget your limited experience.
The whole point is that there has been no universal standard, so I am
in difficulty understanding why you are disputing this basic fact when
it has been authenticated.

I can understand now that pots marked 'Log' or 'Lin' are a much safer
method.

You're unlikely to find pots marked log or lin any more in my considerable
experience..
Graham

Quite true Graham, but your considerable expeience is not considerable
enough. Even in my limited experience, we do get pots marked Log, or
Lin. That is fact.

Peter Dettmann

 

[Eeyore]

Peter Dettmann wrote:

Eeyore wrote:

From the 1992 Dick Smith catalogue, the following are stated:
A = Linear
B = Logarithmic
C = Logarithmic
E = Anti-Log
J = Linear

Dick Smith is wrong.

In your realm he may not be right, but he is certainly not wrong.

On looking through my junk box, all the C's all measure as log, and
all the A's are linear. Another designation I found was W which is
a Wire Wound pot.

*JUNK BOX* i.e. nothing modern of course.

You have to read the whole thing, and forget your limited experience.
The whole point is that there has been no universal standard, so I am
in difficulty understanding why you are disputing this basic fact when
it has been authenticated.

My alleged 'limited experience' includes designing mixing consoles for Neve, DDA
and Studiomaster. I ma quite intimately familiar with pot specs in fact.

Whereas you have nothing more than 15 year old Australian hobbyist catalogue to
offer.

I suggest you start by examining the taper drawings on page 4 of this document.
http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Potentiometer/InsulatedShaft/RK11K11/RK11K11.PDF

Yes, some companies use other designations (American makers especially) but
you'll find the Alps laws widely copied. and they're as close to a 'standard' as
I know. Several of them are JIS ( Japan Industry Standard).

Graham

 

[Peter Dettmann]

On Thu, 02 Aug 2007 14:33:10 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Peter Dettmann wrote:

Eeyore wrote:

From the 1992 Dick Smith catalogue, the following are stated:
A = Linear
B = Logarithmic
C = Logarithmic
E = Anti-Log
J = Linear

Dick Smith is wrong.

In your realm he may not be right, but he is certainly not wrong.

On looking through my junk box, all the C's all measure as log, and
all the A's are linear. Another designation I found was W which is
a Wire Wound pot.

*JUNK BOX* i.e. nothing modern of course.

You have to read the whole thing, and forget your limited experience.
The whole point is that there has been no universal standard, so I am
in difficulty understanding why you are disputing this basic fact when
it has been authenticated.

My alleged 'limited experience' includes designing mixing consoles for Neve, DDA
and Studiomaster. I ma quite intimately familiar with pot specs in fact.

Whereas you have nothing more than 15 year old Australian hobbyist catalogue to
offer.

I suggest you start by examining the taper drawings on page 4 of this document.
http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Potentiometer/InsulatedShaft/RK11K11/RK11K11.PDF

Yes, some companies use other designations (American makers especially) but
you'll find the Alps laws widely copied. and they're as close to a 'standard' as
I know. Several of them are JIS ( Japan Industry Standard).

Graham

Sigh ..... Graham, you again miss the point. You seem to state
unequivocally that a C taper is nor ever has been used anywhere
regularly as a Log taper. You based this on your wide experience.
Well my friend, your wide experience is obviously not wide enough.

Your experience on some mixing consoles is commendable, but hardly
adequte. My limited though wider experience on radio repair and
electronics, over several decades of design and manufacture show that
your bald statement is only true in a limited area. I did not
consider that an astute person would need more than one reference to
show that the C Log taper is and has been used. Live with it.
As I said earlier, this has been in use since at least the early
1950's, but obviously not universally (I already agreed to that
previously).

What is or is not standard now is not the question, if you read
carefully the matter dealt with what was used, and that is not in
doubt. C taper was certainly used extensively, and for many years as
a Log designator. You have not shown otherwise. End of story.

Peter Dettmann