Re: tool changer logic- mathematical challenge

Hello,
You seem to be on the right track, but not there yet. You have to
think of it as this;

What angle of opening, will create 2 trip points, so that sensors at
90 deg. to eachother will trip every 45 degrees?

Imagine an arrangement of 4 sensors at 90 deg. "+" represented by a
crosshair. Now imagine a "C" shape. Put the + into the C and align
one point of the + with one of the endpoints of the C. This
represents a trip location.

Now forget about the currently tripped sensor, look at the next
one, which is currently out in the opening of the C. We want this
one to trip in another 45 deg of movement. So, 90 (between adjacent
sensors) and another 45 deg. of movement for the not-tripped sensor
give 135 degrees.

If you lay it out in CAD you will see that every 45 degree
rotation causes one of the 4 sensors to trip on one side of the 135
deg C opening every time. However, this means that I will have to
check each sensor for when the go from 0 to 1 and for when each goes
from 1 to 0. In other words, it appears I will need 4 active LO and
4 active HI inputs to read the position of the turret. Also, one
output for a DPDT forward/reverse relay.

I'm not so sure Mach2 with 2 parports will do this. I'm kinda
thinking about a small $99 PLC with 8 inputs and 6 outputs to do the
tool turret. Mach2 will just send a 'start' signal to tell the PLC
to run it's program, then maybe recieve a 'done' signal from the PLC
after the tool change is complete etc... Got some thinking to do on
this.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "industrialhobbies"
<admin@i...> wrote:

> This is just a WAG (wild ass guess).
>
> To do it with only one sensor active (or not) at a time 45 degree
> opening 22.5 degrees out of angular alignment with the number 1
> position.
>
> That would meet the requirement of a single sensor (of four), and

in

> this case any opening between 22.5 and 45 degrees would work.
>
> Somewhere else you mentioned a backup circuit, backing up to hold
> position, you would need to change the angular alignment from 22.5
> degrees out, to 0 degrees (just enough to trip the sensor). That
> would allow you to index all the way around through each of the 4
> sensors and change the state of one sensor at a time, based on only
> 45 degrees of motion.
>
> The offset of angular alignment is only needed for real world
> applications, theoretically it's not needed.
>
> Thanks
> Aaron Moss
> www.IndustrialHobbies.com
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lance Hopper"
> <snaggletto@c...> wrote:
> > Test yourself, see how good you really are...
> >
> > Given; a ratcheting action, rotary tool turret with 8 positions

(a

> > tool every 45 degrees). The turret can only index going one
> direction.
> >
> > Given; a series of 4 optical sensors, spaced evenly @ 90 degrees
> > around a circle.
> >
> > Given; a "C" shaped, semi-circular raised area that passes thru

and

> > blocks/unblocks the optical sensors as it rotates with the tool
> > turret. This creates 2 state change areas for each of the 4
> > sensors. Assuming the "C" shape, and CCW motion, you can see

that

> > each of the 4 sensors will go from blocked to unblocked, and
> > unblocked to blocked as the turret rotates.
> >
> > Problem; how many degrees is the opening of the semi-circular "C"
> > shape that will create an off - on and on - off transition for

each

> > of the 4 sensors. Resulting in an index resolution of 45 degrees
> > when only looking at one sensor at a time.
> >
> >
> > This is easier than it first appears, however, I never could

figure

> > it out without help. I thought this might be an interesting
> > challenge for others. See what you come up with. Good luck.