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Unread 01-24-2004, 07:58 PM
Jay Lundy Jay Lundy is offline
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Bourns 6539/6639

http://www.bourns.com/2/pdfs//6539.pdf

It says it is continuous, but it's effective electrical rotation is 340 deg. So is there a 20 deg region where there is no change in resistance?

Also does it have a max RPM? I would assume yes but there isn't one listed in the datasheet.
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Unread 01-25-2004, 01:13 AM
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Re: Bourns 6539/6639

I believe that the Mechanical Angle area says that models with stops at 340deg are available. There is also a Rotational Life listed as 10,000,000 shaft revolutions, which might help you to determine a property like max RPM. If you know your RPM at the shaft, you can calculate life expectancy.

Depending on the application, I would suggest using a rotary encoder instead of a potentiometer. We used this style of potentiometer on our swerve system, last year, to keep track of the angle of our wheel modules, and it worked great, but in that case, there was very little load on the pot's shaft, and it didn't have to rotate very much, very quickly. If you're looking for a high speed kind of thing, I think I would suggest looking into rotary encoders. Even the lower resolution encoders from DigiKey seem like they could be very useful. Say you have 8 inch diameter wheels (and you're using 1:1 ratio between wheel rotation and encoder rotation) and are using them with an encoder whose resolution is 32 ticks per rotation, that's approximately 1.3 ticks per inch, or 0.8 inches per tick.

Dunno, just a thought.
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Unread 01-25-2004, 03:23 AM
Jay Lundy Jay Lundy is offline
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Re: Bourns 6539/6639

We are planning on using these for our arms, so we want really good resolution that we can only get with a pot or a really expensive encoder (I've seen ones with 1024 ppr, but those require interrupts and more processor power).

It looks like our setup won't be needing a high RPMs, so that doesn't really matter. But if there is a region of rotation where the input doesn't change then we can't use this pot.
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