[rusmannx]

I have a C3 pulse index card for my G0602 (working great), and am going to add a second spindle sensor so LinuxCNC sees both an index pulse and a phase pulse. I really have no idea why I'm using the C3, other than everyone else does it.

What exactly does this card do, and why can't I just run the sensor right to my breakout board (mine is a C11)? Would running the sensor straight to the BOB input (instead of the C3) not work? Or is it just not ideal?

I don't mind buying a second C3, just trying to understand its function.
Thanks.

[Fastest1]

Why would it be any different than running the same type of switch for a limit? The only thing that would be a concern is the ability to read the signal fast enough. I run my limits direct, well with a resistor but that is it. Try it.

[cyclestart]

What exactly does this card do

Seeing as this went unanswered......
I'm not an electronics guy by any stretch and will gladly stand corrected on what follows, I've learned lots from posters correcting
my baloney

The main thing the C-3 will do in your application is provide a comparator circuit (schmitt trigger?). The signal output and the
sensor are parallel so some current is present at signal even if the sensor is closed The comparator provides true on/off.
The C-3 also appears to have a capacitor across 5+/ground and some resistors to limit current. The basics of the C-3 can be
seen in this link:
DAK Engineering - CNC Threading

Would running the sensor straight to the BOB input (instead of the C3) not work?

The optical limit switch sitting on my desk has a 15 microsecond transition time, faster than 60 slot encoder at threading rpm. How well
it would work without further clean-up I don't know. Why not experiment ? Sounds like good geeky fun if you have the time.

[analogman]

Like cyclestart says, it cleans up the input signal into a nice digital signal.

To add to the "geeky fun" If you have access to a two channel scope (with decent input impedance), put a channel each on the input and output and you will see the difference.

[rusmannx]

That's sorta what I figured. I'm only a little familiar with Schmitt Triggers so I'll read up on that just for fun. I don't have access to a scope but I was thinking the same thing. I may need to have one of my friends bring his over so I can play with it.

Thanks!

[cyclestart]

Linuxcnc has halscope
Attachment 309086
The top signal is a C3 picking up an index, the bottom signal is a cheap optical limit switch reading 60 slots/rev. Looks much the same to my untrained eye.
Ignore the uneven phase-a spacing, the encoder disk used was pretty dodgy.
This was only tested up to 600 rpm (again the dodgy disk), at higher speeds the C3 may show it's advantage.

One thing about the C3 is the 'throat' is kind of shallow restricting how far the beam can be from the outer edge of the disk.
If anyone finds this useful great. If not I killed a cold winter day and had some fun doing it.

[mactec54]

Linuxcnc has halscope
Attachment 309086
The top signal is a C3 picking up an index, the bottom signal is a cheap optical limit switch reading 60 slots/rev. Looks much the same to my untrained eye.
Ignore the uneven phase-a spacing, the encoder disk used was pretty dodgy.
This was only tested up to 600 rpm (again the dodgy disk), at higher speeds the C3 may show it's advantage.

One thing about the C3 is the 'throat' is kind of shallow restricting how far the beam can be from the outer edge of the disk.
If anyone finds this useful great. If not I killed a cold winter day and had some fun doing it.

Good job, it's always interesting to see what others do with there software, You did say the disc was not accurate, but is the disc that far out, the spacings are not very good, it would be interesting to see the C3 with the same disc, the form is not going to change that much, the spacing accuracy is what needs to be accurate

[cyclestart]

The disk looks like it was carved with a butter knife. It was cut on a cnc router but the mystery material gummed up the cutter.
So yeah, pretty bad. When I find a better piece of sacrificial material the experiment will be run again with both units running on the same ring of slots, At higher rpm too.

[rusmannx]

Linuxcnc has halscope
Attachment 309086
The top signal is a C3 picking up an index, the bottom signal is a cheap optical limit switch reading 60 slots/rev. Looks much the same to my untrained eye.
Ignore the uneven phase-a spacing, the encoder disk used was pretty dodgy.
This was only tested up to 600 rpm (again the dodgy disk), at higher speeds the C3 may show it's advantage.

One thing about the C3 is the 'throat' is kind of shallow restricting how far the beam can be from the outer edge of the disk.
If anyone finds this useful great. If not I killed a cold winter day and had some fun doing it.

Very cool. Thanks for posting