arhi has a mystery dual-increment potentiometer:
there are 2 pots inside … example, you turn the pot fully to the left. let’s say it is 10K, then you rotate it to the right, and it goes “easy” rotating to the right almost a full circle (few degrees shy from a full circle) and that goes from 0 – 170R to the half of the circle and then start to drop to 128 ohm at the end of the circle (I’m measuring right now), then it gets “bit harder to rotate it” – you feel you catch up and you are rotating something else, now you can continue and now each degree is not changing by few ohm as it was until this moment but now it is more like 100R per degree (~100 times more) .. you turn it a half circle to the right and you get to 5k5 .. then if you back to the left it reduces again by below 2R per degree so a full turn back now will get you down to 5K3
Via the forum.
they use those without limit that make infinite rotations for weather stations, to detect the wind direction
datasheet in Russian – http://www.trigger.ru/include/sp5_35.pdf
Hi Raivis, maybe you know some source for acquiring those?
this is home page of producer of those potentiometers http://www.rikor-electronics.ru/ try asking them. in smaller quantities look east, find some friends in some CIS country (Russia) and ask them to acquire those pots for you.
Rather than trying to describe in words, a graph relating rotation angle to resistance would be invaluable.
http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ru&tl=en&u=http%3A%2F%2Fwww.rikor-electronics.ru%2Fitem_9.html&act=url
“googlated” datasheet, no nonsense translation :)
From data-sheet: “Endurance, cycles 5000”. Cool idea though. Apple must be preparing the patent application right now just to make sure they’re “first to file”.
Jason, it would not be simple to graph it as at 90 degrees you can have 500 different values for your pot, depending on “how you got to 90 degrees position” … also not really too relevant for the whole story.. as the graph is different for a different value pot … the “principle” is what is interesting
Raivis, thanks a bunch, lot of friends in CIS so I’m sure I’ll manage to get some if that company still sell’s them (in small quantities and for reasonable price)