Re: Re: EMC spindle speed control

From: "Marty Escarcega" <escarcega@...>
<s>

>just use 3 control relays, FWD, REVERSE, STOP

Maybe two unless you need a spindle brake. I had a pair of relays
wired up before NAMES that did this for my Grizzly. I never built them
into the box 'cause we changed boxes. They work fine with my steppers and
an extra parport.

>Now the spindle speed control, only thing I can think of is to use
>the control input of a VFD. Once set, don't the VFD's remain pretty
>constant?

Well if Jon E. is right about the analog output code. For an open loop
spindle you would just have to scale the VFD to the voltage out from the
DAC.

>Feedback would be another issue. Only thing I could
>think of is a rotary encoder like the one Dan Mauch sells to provide
>feedback to EMC/Computer.

For closed loop we would just have to find a way to get the encoder
pulses back into the EMC and some way to close the loop between pulses and
DAC. My preference here would be to treat the spindle as just another
rotary axis. I think that a small change would be needed to reset the
angle to 0 for each rotation. EMC currently uses wrapped linear for it's
rotary axis definition.

>So, am I way out in left field? :-) Or reasonably close to home
>plate?

Close enough!

Ray