[sdiy] Pot life specifications

[Tim Parkhurst]

On Fri, Aug 21, 2009 at 1:39 AM, George Hearn<georgehearn at btinternet.com> wrote:
>
> It's quite easy to get an indication of how good the pot (or encoder) life
> is by this method;
> 1. Take a pot and hold it in a vice with the shaft exiting upward.
> 2. Using a retort stand or other method, suspend a dill above the pot, on
> axis, and with the pot shaft in the drill chuck.
> 3. Start the drill and leave to run for 10,000 revolutions or more.
> 4. Mechanical wear can be additionally simulated by having the drill
> slightly off axis causing an additional wobble.
>

I don't think this is an accurate measure of pot life for a couple of reasons:
1) Most pots don't turn all the way around (360°), so you're going to
need a limiting / reversing mechanism.
2) The heat generated by continuous motion would not be the same as
generated by "normal" use. This heat would definitely shorten the life
of the pot and not give you an accurate projection of real world
longevity. An automated test like this would need to turn the pot,
wait for a second or two, and then turn the pot back. You end up
needing something with a timer and a (small) washing machine gear
mechanism. I've been involved in testing like this at Apple, and you
have to take all sorts of little details into account.


Tim (doesn't turn all the way around either) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings