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Author Topic: 10K pot without stop  (Read 2124 times)
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Manchester (England England)
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they have about 27 degrees of dead band,
It is probably because they are cheap, try these:-
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0173580
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I have posted links to pots with no stops in the past.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12426TR-ND

Will have a small range where no output is availalble.

Crossroads OPTS to POST POTS w/no STOP. SPOT on!
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Dang, that was pretty clever tastewar! Nice smiley-cool

How about this for the dead spot - put two back to back on the same shaft, offset by 90 degrees.
Then as one spins thru the dead spot the other will still be increasing, until both are active then the increase will be greater, until it drops down at the next dead spot.
I figure one 500ohm pot, one 10K pot, should plot out something like this:
Not too bad for $1.20 or so ...
« Last Edit: May 13, 2011, 11:34:48 pm by CrossRoads » Logged

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Hmm, looks like 500 ohm not an option.
There's these that are a little more expensive, $6 vs $0.65, no indication if they have a dead band, and they have detents if that will come on handy.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12427CT-ND

Do some googling, you're  looking for 'potentiometer, continuous'
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The panasonic part? Where are you seeing that? I looked all over and couldn't see any info.
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I see now, no detent stops between 270 around to 90.

Well, I like my original way them have to see what it does with 2 10Ks back to back,might be too odd of a resistance jump to be usable.
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Like I said, 27 degree dead band.

In the digikey catalogue they say 347 degrees, but if you look at the graph linked to by digikey (http://media.digikey.com/pdf/Data%20Sheets/Panasonic%20Resistors%20Thermistors%20PDFs/EVWAE4001B14.pdf) it doesn't start ramping up untill just over 13 degrees then stops at 347.

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If one can find pots that are easy to stack, then two pots might be used, one as the master and the second as backup for gap coverage in the first. Both pots would need to be monitored such that when the master pot (assuming the pots have ~270 deg of coverage each and are offset 180 deg from each other) had an output value of less than 60 deg or more than 210 deg, the position of the backup pot would be used with its known 180 deg offset.  
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That sounds like a plan, similar to what Crossroads was getting at I think.

Dual pots are common but I've never had a good look to see if it's practical to separate them and remount out of phase. If so I'd be inclined to use 180 degrees each with a little hysteresis at the crossover points.

Getting back to using rotary switches, the OP said he doesn't want detentes but with most of those switches you can remove the ball bearing and make them smooth.

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Thanks everyone for your responses.  I did find a supplier of "servo pots" on ebay and bought one.  The value went haywire as it went through from high to low and after some coding I fixed that but the rotary encoder method proved the best.

Bought a dozen from HK.
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I did find a supplier of "servo pots" on ebay and bought one.  The value went haywire as it went through from high to low

"Haywire"?  That is exactly how a pot is designed to work.
Which is why a pot is not as good for continuous applications as several other solutions.

The pot was an easy answer.  It used one port and little programming so I thought that I wold give it a try.  The encoder works great though.
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