low friction potentiometers and 360 degree servos

[Sling]

Hi I need to find a low friction degree potted potentiometer - standard specs for use as a microcontroller input, something like 50k ohms or whatever. The main thing is that it is low friction.

Also I'd like to find servos that can rotate 360 degrees or near that. Ideally something with similar dimensions to the Futaba s148 but with full rotation without the need for external gears.

 

[dknguyen]

Around what diameter for the pot? Ball bearing pots are everywhere but I've never seen one that is board mount or smaller than 2cm. THey tend to be quite expensive though. This is one example available at Digikey and likely mouser and others costs $50 for the ball bearing version. A little less than half that for the bushing version:
https://www.electro-tech-online.com/custompdfs/2010/10/157.pdf

How low friction do you need? What is this for?

Servos...yeah I've not see one that can turn past 180 degrees (and even then it oftentimes that requires little modification). There are sail winch servos but they are larger sized. And landing retract servos don't have variable positioning- it's one extreme or the other.

There are the AX, RX, DX, and EX servos that www.crustcrawler.com sells. They aren't regular PWM-RC servos however. THey accept RS-485 and some of them can get to be very very pricey (mainly the larger ones).

 

[Sling]

Interesting! Well 2cm for the potentiometer diameter is fine as long as it turns easily. Its purpose is to sense wind direction, and I'll be attaching it to a wind vane.

Originally I was thinking of using two potentiometers actually, one for the horizontal plane and another for a vertical angle (pan and tilt angles so to speak). However the vertical angle would only work if the potentiometer was almost frictionless, due to gravity, and I doubt I'd be able to find that, so I'm thinking of using a bank of tilt sensors instead. Not sure how well that would work but I'll give it a try.

So ball-bearing (or servo mounted?) potentiometers don't have so much friction... great I'll try one for the yaw angle. Thanks.

Regarding the 360 rotating servo, yeah I've pretty much given up on finding one of those. I think I'm going to use a 2:1 teeth ratio gearing system and build a standard servo into a housing for that.

 

[cr0sh]

Have you thought about using a digital encoder instead of a potentiometer? An 8-bit encoder would give you 256 position values. If you didn't need a lot of accuracy (and didn't mind a larger size), you could use a magnet and multiple reed switches (or hall effect sensors?). Another idea might be a pair of nested concentric coils; drive one coil with a DC pulse, and the strength/polarity on the other coil should give you information about the position of the coils...