Precision wirewound pot wiper bounce?
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From: oparr on 13 Jul 2010 12:00 > Can you think about why they are only one turn devices? No, you? ;) BTW, Bourns makes a Hybritron® Element 10-turn pot, what exactly is that, some sort of hybrid I presume? They seem to be used in game controllers. > It would matter if it is a setting where the pot is going to be used > constantly, like in a power supply voltage setting knob or an audio amp > volume control. Agreed, my experience so far seems to be that they perform poorly while in motion. On Jul 13, 11:28 am, AM <thisthatandtheot...(a)beherenow.org> wrote: >
From: oparr on 13 Jul 2010 12:12 > There must not be an open wiper circumstance at ANY time during the > operation of the pot... ever. Well, Bourns does give a wiper bounce time of .1ms for their precision wirewound and hybritron pots. Not certain whether that's the norm or coincides with a vibration/shock condition. Whatever, all indications are that the wiper of the pot in question is losing contact with the element. I'll probably request a replacment but my hopes aren't all that high. On Jul 13, 11:47 am, AM <thisthatandtheot...(a)beherenow.org> wrote: >
From: oparr on 13 Jul 2010 12:17 > We use a lot of the Bourns 3590 sereis ten turn pots. I'm using the pot to vary the voltage to the VCO input of a function generator. A 1-turn pot is a bit coarse and I estimate that a 10-turn pot is going to be too fine. The 3-turn pot is just right except for the mentioned issue. I'll try replacing that first. Thanks! On Jul 13, 11:43 am, George Herold <gher...(a)teachspin.com> wrote: >
From: whit3rd on 13 Jul 2010 15:28 On Jul 13, 9:17 am, "op...(a)hotmail.com" <op...(a)hotmail.com> wrote: >[ about a scratchy potentiometer] > I'm using the pot to vary the voltage to the VCO input of a function > generator. A 1-turn pot is a bit coarse Ah, this is a low-voltage potentiometer? Switches and pot wipers get very reliable at 100V and up, but fail a lot in the 1V range (because the thin film of dust and dirt is enough to insulate the low voltage). That's why a lot of low-voltage circuitry design avoids wiper contacts. I take exception to the advice to 'not draw wiper current'. Sometimes you can fix dirty pots in-situ by doing exactly that. It carbonizes the oily film... Same with switches.
From: David Eather on 13 Jul 2010 17:09
On 14/07/2010 12:34 AM, oparr(a)hotmail.com wrote: > Recently bought the 3-turn wirewound pot below to replace a worn 1- > turn conductive plastic pot; > > http://media.digikey.com/photos/Vishay%20Spectrol%20Photos/533,534,535%20SERIES.jpg > > Out of the box, the thing exhibits wiper bounce or something similar. > Every now and then the wiper appears to momentarily lose contact with > the element while turning the knob. I would expect that with a worn > pot but not a new one. Is this a bad pot or is this a caveat with > wirewoud pots? > > Other new conductive plastic and cermet pots work just fine, however, > can't get them in anything other than 1-turn. These are 3 turn conductive plastic - 10k and 5k http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6023740 http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6023756 |