Precision wirewound pot wiper bounce?
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From: Mycelium on 14 Jul 2010 13:07 On Wed, 14 Jul 2010 10:02:08 -0700 (PDT), "oparr(a)hotmail.com" <oparr(a)hotmail.com> wrote: >The pot in question spreads the resistance linearly over 1080 degrees >rotation of the knob. I think you misunderstood the poster who >mentioned the planetary mechanism used on **some** multiturn pots. You don't seem to understand. It matters not how many turns it takes if the actual wiper is only making a single turn. The lineal distance the wiper takes and length of the resistance medium is what matters. Making a mechanism to spread a single turn out to three does not give one better, less noisy resolve or stop point achievability. I understood him perfectly. One CAN take a ten turn and step DOWN to a lower turns count and keep high resolve and stepping. One cannot get there going the other way. It is 100% counterproductive and gives a false sense of higher precision where none exists.
From: oparr on 14 Jul 2010 13:51 > I understood him perfectly. In that case, when/where did he say that the 3-turn pot in the link below uses the mechanism you just described; http://media.digikey.com/photos/Vishay%20Spectrol%20Photos/533,534,53... If he didn't then why have you assumed that is the case on your own? Nothing to do with the fact that it isn't a 10-turn pot I hope? On Jul 14, 1:07 pm, Mycelium <mycel...(a)thematrixattheendofthemushroomstem.org> wrote: >
From: Mycelium on 14 Jul 2010 14:29 On Wed, 14 Jul 2010 10:51:59 -0700 (PDT), "oparr(a)hotmail.com" <oparr(a)hotmail.com> wrote: >> I understood him perfectly. > >In that case, when/where did he say that the 3-turn pot in the link >below uses the mechanism you just described; > >http://media.digikey.com/photos/Vishay%20Spectrol%20Photos/533,534,53... > >If he didn't then why have you assumed that is the case on your own? >Nothing to do with the fact that it isn't a 10-turn pot I hope? > >On Jul 14, 1:07�pm, Mycelium ><mycel...(a)thematrixattheendofthemushroomstem.org> wrote: >> I never said that he said anything. I only referred to what I referred to. It had nothing to do with him other then that he spurred my thoughts on the matter. Are you all caught up now?
From: Spehro Pefhany on 14 Jul 2010 14:57 On Wed, 14 Jul 2010 09:41:15 -0700, Mycelium <mycelium(a)thematrixattheendofthemushroomstem.org> wrote: >On Wed, 14 Jul 2010 08:43:17 -0700 (PDT), "oparr(a)hotmail.com" ><oparr(a)hotmail.com> wrote: > >>> Especially if it is simply a set point pot on a circuit. >> >>The pot in question is not a trimmer pot. Long story short....I would >>not be able to simulate fast acceleration/deceleration, using fingers >>alone, with a 10-turn pot. This is a somewhat "outside the box" use >>of a function generator. >> >> >>On Jul 14, 10:40�am, Mycelium >><mycel...(a)thematrixattheendofthemushroomstem.org> wrote: >>> > > > OK, then make a chain and sprocket reducer/overdrive. > > Then you can make it turn ten times to your three-on-the-fingers >or whatever ratio you come up with. > > THAT scenario is far better than buying a pot where they took a single >turn pot and made it take 3 turns to turn it. Taking three turns to turn >a ten turn pot is a far higher resolution adjustment from a 'noise' POV, >with 'noise' being transition spikes made between wire contact nodes. > > They should sell ten turn pot assemblies where the user can make the >ten in less turns based on what gears he puts in the box. > > Just like the drill press pulley arrangements. > > Naaahh.. too much like mechanics for the engineers to grasp that one. Single turn pots have better symmetry than multi-turn pots, so they might behave better with temperature changes. Back when analog instrumentation was common, I designed instruments with big custom single-turn WW pots and with a gear train which stepped up 270 degrees or whatever it was 6" or so diameter dial (144mm x 144mm DIN standard) to a 3:1 turn helical pot (same construction as the 10 turn pots, but we didn't like the friction from a 10:1 ratio) wot we got from some outfit out in Oceanside CA (I think it was actually a Japanese part). The user interface had to be a single turn dial for the direct reading deviation to work.
From: oparr on 14 Jul 2010 17:00
> Are you all caught up now? Yes....Someone silly this way came. On Jul 14, 2:29 pm, Mycelium <mycel...(a)thematrixattheendofthemushroomstem.org> wrote: > |