[sdiy] Knobs with LEDs

[Tom Wiltshire]

On 2 Apr 2011, at 11:07, Graham Atkins wrote:

> On 2 Apr 2011, at 06:42, Tristan wrote:
> 
>> I guess the intent is only to provide indication over the approximately 300 degree range of a rotary
>> potentiometer.
> 
> But it states it is for rotary encoders.....By nature a 360 deg device.

That's true, Graham, but often rotary encoders are used to alter a parameter from min to max, and that implies some end points, just like a pot. They might be endless, but they're mostly used to *replace* a pot, like on the Nord synths, in which case you've got something that acts pretty much like a pot, but has programmability and instant indication of stored positions.
The problems are more to do with the limited resolution of both the encoders (often 24 positions) and LEDs (often 15 or 31 LEDs) in my opinion. The limited display resolution makes an associated LCD display more or less essential for detailed editing, and the limited encoder resolution makes it hard to do a smooth filter sweep (for example) in a single movement because you have to give the encoder several full rotations.
I also agree with Paul that if you're going to design a board for such a gizmo, it'd have been sensible to (a) put the encoder on the board and (b) add enough intelligence for the board to deal with the encoder and display so that the host system doesn't have to.

T.