Re: Handwheel & Joystick

"Arne Chr. Jorgensen" wrote:

>
> 2. Hand wheel: ( Fred )
>
> I had the same questions about when I suggested this for the
> manufactor. There is several ways to do this, - and I will just
> mention one:
> You just use it in manual mode, - and take the input from the hand
> wheel as the encoder feedback ( toggle switches to select axis ).
> This will offset your actual position, - but it doesn't matter.

Yes, it does matter. EMC currently keeps track not only of coordinates
referenced to a part position, but also always keeps track of the machine's
physical position, relative to the 'Home' position. This is very valuable,
as it allows software to prevent crashing into the limit stops, and also
allows one to later add in a machine error compensation able that
corrects known errors in the leadscrews. What is worse, is this
hardware scheme would generate (small) false moves as you switch from
machine encoder to hand encoder, because there is a 75% probability
that the encoders are not at the same quadrature values when you make
the switch. Anyway, the extra encoder counters are there on most
STG boards (the minimum STG card is 4 axes).

Jon