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Centre tapped potentiometers (Read 208 times)
Nov 10th, 2006 at 9:18am

Padser   Offline
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~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

 
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Reply #1 - Nov 16th, 2006 at 6:35am

Padser   Offline
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Mmm, is this a stupid question or something?

Roll Eyes

TTFN

Pads
 
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Reply #2 - Nov 17th, 2006 at 8:48pm

chuckcrc   Offline
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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
 
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Reply #3 - Nov 18th, 2006 at 8:15pm

beaky   Offline
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Google and Wikipedia; perhaps you've heard of them... Grin

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.
 

...
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Reply #4 - Nov 20th, 2006 at 7:09am

Padser   Offline
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~S~

Thanks for the input.

Ahem, I had actually read the Wikipedia entry but I'm afraid it left me none the wiser...  Roll Eyes 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
 
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Reply #5 - Nov 20th, 2006 at 2:22pm

beaky   Offline
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Quote:
~S~

Thanks for the input.

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


I was teasing, of course... I'll admit I had to look for more info after reading the Wiki entry, also... I couldn't quite find the words to describe what they're actually used for. An engineer must've written that article... sigh...Roll Eyes  Wink

And yes, they are commonly used in industrial joysticks that use pots... are you thinking of building a stick from scratch?
 

...
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Reply #6 - Nov 20th, 2006 at 6:12pm

Padser   Offline
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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  Roll Eyes, 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  to show the innards, but they're not great, I'll see about taking some better ones.

...
...


I built the gimbal out of old meccano pieces and built in a 4-to-1 gearing system to increase the throw of the pots from about 10 degrees to about 40 - enough for Windows default joystick driver to calibrate effectively anyway.

I'm currently working on version 2 as a project at a metalwork/modelling class at a local college - learning to use lathes and milling machines and what-not - very interesting and another new area that this obsession... er... hobby has got me into...  Wink

I'm looking into possible potentiometer sources for the new stick (hence the question) and for a throttle quadrant I'm planning, too - I'm looking to make a GA version first with the push/pull engine controls. More of that to follow when it takes shape - it's little more than a fag packet sketch at the moment, but will probably use slider track pots (you can get ones with a 10cm travel, which should be just enough to feel about right)...

Cheers,

Pads
 
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Reply #7 - Nov 20th, 2006 at 9:10pm

JBaymore   Offline
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pads,

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

best,

......john
 

... ...Intel i7 960 quad 3.2G LGA 1366, Asus P6X58D Premium, 750W Corsair, 6 gig 1600 DDR3, Spinpoint 1TB 7200 HD, Caviar 500G 7200 HD, GTX275 1280M,  Logitec Z640, Win7 Pro 64b, CH Products yoke, pedals + throttle quad, simpit
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Reply #8 - Nov 27th, 2006 at 6:51am

beaky   Offline
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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!!
 

...
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Reply #9 - Nov 27th, 2006 at 4:54pm

Fozzer   Offline
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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
 

Dell Dimension 5000 BTX Tower. Win7 Home Edition, 32 Bit. Intel Pentium 4, dual 2.8 GHz. 2.5GB RAM, nVidia GF 9500GT 1GB. SATA 500GB + 80GB. Philips 17" LCD Monitor. Micronet ADSL Modem only. Saitek Cyborg Evo Force. FS 2004 + FSX. Briggs and Stratton Petrol Lawn Mower...Motor Bikes. Gas Cooker... and lots of musical instruments!.... ...!
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Reply #10 - Nov 27th, 2006 at 8:43pm

JBaymore   Offline
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Fozzer,

I knew there was a reason we kept you around.   Grin


best,

..................john
 

... ...Intel i7 960 quad 3.2G LGA 1366, Asus P6X58D Premium, 750W Corsair, 6 gig 1600 DDR3, Spinpoint 1TB 7200 HD, Caviar 500G 7200 HD, GTX275 1280M,  Logitec Z640, Win7 Pro 64b, CH Products yoke, pedals + throttle quad, simpit
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Reply #11 - Nov 28th, 2006 at 1:57pm

beaky   Offline
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Quote:
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... Roll Eyes   Wink

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...  Wink Grin
 

...
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Reply #12 - Nov 29th, 2006 at 7:00pm

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

best,

.......................john
 

... ...Intel i7 960 quad 3.2G LGA 1366, Asus P6X58D Premium, 750W Corsair, 6 gig 1600 DDR3, Spinpoint 1TB 7200 HD, Caviar 500G 7200 HD, GTX275 1280M,  Logitec Z640, Win7 Pro 64b, CH Products yoke, pedals + throttle quad, simpit
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Reply #13 - Nov 30th, 2006 at 9:25pm

beaky   Offline
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Quote:
Nah... Fozzer must have been in management.... taking credit after the fact for the front line guy's ideas and work!   Wink

best,

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


Managers, engineers... same thing. Wink

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... Grin
 

...
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Reply #14 - Dec 1st, 2006 at 3:02am

Fozzer   Offline
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Quote:
Oh, fine... now the EE weighs in...and simply repeats what I said, only with more jargon and trivia!  ...Baxandall... Roll Eyes   Wink

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...  Wink Grin



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

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



Quote:
Managers, engineers... same thing. Wink

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... Grin


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

If so you will get no more amazing electronic tips from me...
...so there... Angry...!

....LOL... Grin...!

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

...Tee-Hee... Grin...!
 

Dell Dimension 5000 BTX Tower. Win7 Home Edition, 32 Bit. Intel Pentium 4, dual 2.8 GHz. 2.5GB RAM, nVidia GF 9500GT 1GB. SATA 500GB + 80GB. Philips 17" LCD Monitor. Micronet ADSL Modem only. Saitek Cyborg Evo Force. FS 2004 + FSX. Briggs and Stratton Petrol Lawn Mower...Motor Bikes. Gas Cooker... and lots of musical instruments!.... ...!
Yamaha MO6,MM6,DX7,DX11,DX21,DX100,MK100,EMT10,PSR400,PSS780,Roland GW-8L v2,TR505,Casio MT-205,Korg CX3v2 dual manual,+ Leslie 760,M-Audio Prokeys88,KeyRig,Cubase,Keyfax4,Guitars,Orchestral,Baroque,Renaissance,Medieval Instruments.
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