[sdiy] rotary encoder failure mechanism

[Neil Johnson]

Hi,

Dave Manley wrote:
> When an encoder becomes unreliable is it because
>
> 1. the switches are worn out
> 2. the switches are contaminated and need cleaning
> 3. the mechanical cam that operates the switches is worn out
> 4. debris from wear on the cam/switches is blocking the switch  
> operation
> 5. ???
> 6. any and/or all of the above?
>
> Anybody take one of these apart and do an analysis?  Does spraying  
> cleaner into an encoder really do anything?

The low-cost ALPS style rotary encoders (e.g. as used in x0xb0x) are  
built in same way as their pots: a little PCB with tracks printed/ 
etched on them, and the spindle moves sprung metal contacts over the  
tracks.  Pots have single or dual carbon (or some other resistive  
material) tracks, encoders have highly conductive patterns to  
implement the A/B codes.

Otherwise same materials, same lifetime, similar failure modes.  No  
cams or anything like that.

Neil
--
http://www.njohnson.co.uk