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Centre tapped potentiometers

PostPosted: Fri Nov 10, 2006 9:18 am
by Padser
~S~ All,

Am looking into a source of potentiometers for my next project and have seen the term 'centre tapped' as an option.

I'm having difficulties getting my head around what this means - can anyone help me out?

What does 'centre tapped' mean and why might it be a useful thing to have?

All the best,

Pads

Re: Centre tapped potentiometers

PostPosted: Thu Nov 16, 2006 6:35 am
by Padser
Mmm, is this a stupid question or something?

::)

TTFN

Pads

Re: Centre tapped potentiometers

PostPosted: Fri Nov 17, 2006 8:48 pm
by chuckcrc
Pads
I 've never heard of that description for a pot before. The only thing I can think of is that it is refering to the pot as having a centre detent position.
These type of pots were used in hi fi system mainly for the balance control as you would want the pot to be exactly halfway for the sound to be equal on both channels. They were also used for the tone controls so you could in theory set your tone controls to flat gain ie 0db

sorry I can't be of any more help ???

cheers
chuck

Re: Centre tapped potentiometers

PostPosted: Sat Nov 18, 2006 8:15 pm
by beaky
Google and Wikipedia; perhaps you've heard of them... ;D

http://en.wikipedia.org/wiki/Center_tap

Granted, it's still a little hazy what these would be useful for... had to read up on it , myself.
Chuck is right, but it doesn't necessarily mean the pot will have a mechanical detent... although any pot with such a detent needs the center tap, which is basically just another lead off it to create a "zero" point- so instead of being, for example, a 0 (ground)-to-5V pot, it will now be a -2.5V-to-+2.5V pot.

Can't see much use for that in a simpit, except maybe for a trim control.

Re: Centre tapped potentiometers

PostPosted: Mon Nov 20, 2006 7:09 am
by Padser
~S~

Thanks for the input.

Ahem, I had actually read the Wikipedia entry but I'm afraid it left me none the wiser...  ::) Thanks for the explanation, it's made it much clearer!

So it is effectively a kind of electrical 'detent' - a means of setting  a zero value, presumably, as the name suggests, at the centre of the potentiometer's range/throw.

Mmmm - mightn't such a central zero point be useful for a joystick axis pot - kind of a built in dead-zone?

All the best?

Pads

Re: Centre tapped potentiometers

PostPosted: Mon Nov 20, 2006 2:22 pm
by beaky
[quote]~S~

Thanks for the input.

Ahem, I had actually read the Wikipedia entry but I'm afraid it left me none the wiser...

Re: Centre tapped potentiometers

PostPosted: Mon Nov 20, 2006 6:12 pm
by Padser
RD,


LOL - I mean it though, thanks for the explanation - electronics is by no means my area, although I am picking up bits and pieces as I go.

Actually I've already built a kind of prototype of a prototype long shaft joystick that is now weapon of choice for flying IL-2 and the little bit of FS that I do nowadays. I wanted to build a stick that felt a bit more like the stick in the little microlight I fly (am learning to fly) when I'm not flying my computer. It looks rubbish  ::), but it works very nicely and does feel more like a real control column. The centering springs are fishing catapult elastic - creates a very nice, smooth feel.

I've attached a couple of pics

Re: Centre tapped potentiometers

PostPosted: Mon Nov 20, 2006 9:10 pm
by JBaymore
pads,

Nice general looking idea there.  Thanks for sharing.  Keep the photos coming.

best,

......john

Re: Centre tapped potentiometers

PostPosted: Mon Nov 27, 2006 6:51 am
by beaky
That is very clever... !!
I've already bit off more than I can chew with my simpit project, and I'm only planning to mod the stick part of my existing X45... wouldn't dream of trying to create a stick from scratch!!

Re: Centre tapped potentiometers

PostPosted: Mon Nov 27, 2006 4:54 pm
by Fozzer
A centre-tapped potentiometer is a potentiometer which has an extra solder tag connected to the centre of the resistance track.

You will see 4 solder tags on the outside:
Tag for the slider.
Tag for one end of the track.
Tag for the other end of the track.

An extra tag on the rear of the potentiometer for the centre tapping on the track.

The were often used in variations of the the Baxandall (TM) Tone Control System for audio amplifiers (tube and solid state) Treble and Bass settings.

VERY difficult to find, indeed I always had to modify a standard potentiometer to obtain the centre tapping....!

Cheers all...!

Paul...Electronics Engineer (Retired).... 8)...!


Note: The centre tap will be the "null point" in the sweep of the slider.

Some examples, including centre tapped types down the list of circuits.

http://amps.zugster.net/articles/tone-stacks

Re: Centre tapped potentiometers

PostPosted: Mon Nov 27, 2006 8:43 pm
by JBaymore
Fozzer,

I knew there was a reason we kept you around.   ;D


best,

..................john

Re: Centre tapped potentiometers

PostPosted: Tue Nov 28, 2006 1:57 pm
by beaky
A centre-tapped potentiometer is a potentiometer which has an extra solder tag connected to the centre of the resistance track.

You will see 4 solder tags on the outside:
Tag for the slider.
Tag for one end of the track.
Tag for the other end of the track.

An extra tag on the rear of the potentiometer for the centre tapping on the track.

The were often used in variations of the the Baxandall (TM) Tone Control System for audio amplifiers (tube and solid state) Treble and Bass settings.

VERY difficult to find, indeed I always had to modify a standard potentiometer to obtain the centre tapping....!

Cheers all...!

Paul...Electronics Engineer (Retired).... 8)...!


Note: The centre tap will be the "null point" in the sweep of the slider.

Some examples, including centre tapped types down the list of circuits.

http://amps.zugster.net/articles/tone-stacks


Oh, fine... now the EE weighs in...and simply repeats what I said, only with more jargon and trivia!  ...Baxandall... ::)   ;)

Must've been a drawing-board-type engineer, not a practical engineer...they always show up after everyone's figured something out by fiddling with it, then take all the credit ...waving their slide-rules around for emphasis...  ;) ;D

Re: Centre tapped potentiometers

PostPosted: Wed Nov 29, 2006 7:00 pm
by JBaymore
Nah... Fozzer must have been in management.... taking credit after the fact for the front line guy's ideas and work!   ;)

best,

.......................john

Re: Centre tapped potentiometers

PostPosted: Thu Nov 30, 2006 9:25 pm
by beaky
Nah... Fozzer must have been in management.... taking credit after the fact for the front line guy's ideas and work!   ;)

best,

.......................john


Managers, engineers... same thing. ;)

Actually, I think Mr. F. was an operational engineer or technician if I remember correctly... so he's OK.
But getting a bit "managerial" now that he's retired... ;D

Re: Centre tapped potentiometers

PostPosted: Fri Dec 01, 2006 3:02 am
by Fozzer

Oh, fine... now the EE weighs in...and simply repeats what I said, only with more jargon and trivia!  ...Baxandall... ::)   ;)

Must've been a drawing-board-type engineer, not a practical engineer...they always show up after everyone's figured something out by fiddling with it, then take all the credit ...waving their slide-rules around for emphasis...  ;) ;D



Nah... Fozzer must have been in management.... taking credit after the fact for the front line guy's ideas and work!   ;)

best,
.......................john




Managers, engineers... same thing. ;)

Actually, I think Mr. F. was an operational engineer or technician if I remember correctly... so he's OK.
But getting a bit "managerial" now that he's retired... ;D


...would you lot be attempting to extract the urine from the venerable Fozzer...;)...?

If so you will get no more amazing electronic tips from me...
...so there... >:(...!

....LOL... ;D...!

Paul...still designing and building various electronic devices during my happy retirement....and not a single Manager in sight... :P...!

...Tee-Hee... ;D...!