Gear cutting with HAL function

I would like begining to built an encoder for use with the spindle, I have at home some capacitive sensor and optical sensor I would like know if I can use this for test ? it's a very big sensor but if just for test.

I think that the sensors are both a bit too big. They will not notice encoder teeth that are small enough to be useful.
The optical sensor might have a small enough active area, but it has a 1mS switching time. even with only 50 teeth on the encoder wheel that limits the spindle speed to <600 rpm (it has to switch twice for each tooth)

> What I need to know for synchronise my spindle with a stepper motor by an encoder ?
That is fairly easy. You use HAL to wire the output of the encoder counter into the input of a step generator, through a scale function.
The HAL code to do that is here:
wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Hobbing
This page explains what the commands in that file do:
www.linuxcnc.org/docview/html/hal_intro_fr.html
and this describes the HAL encoder function:
www.linuxcnc.org/docview/html/hal_rtcomps_fr.html#sec:Codeur

Note that the HAL file listed on the Wiki does not include any of the "normal" HAL file things, such as setting up the other axes or loading the spindle encoder counter. All that is listed there is the extra hobbing stuff.

Andy use 3 optical sensor and I would like know why use 3 sensor ?

A typical spindle encoder uses 2 channels for quadrature and in index channel for alignement. This allows rigid tapping (threading holes with a tapping tool held rigidly in the spindle. Quadrature gives both angle and direction information, whereas a single channel only gives angle. If you look at my video, when I turn the spindle backwards and forwards the workholder turns backwards and forwards.
You can almost certainly manage with only one sensor, and an encoder set to counter mode.

Also, how I must determinate the resolution for the encoder ?

The higher the resolution the better. However you will be limited by the space around the spindle, the sensing diameter of your sensors, the speed of your sensors and the speed of the parallel port. (And the speed of your interface circuit)
don't expect to sample at much more than 10kHz through the parallel port.

when I speak about this sensors, it's just for test passing my hand in front, and check if the system works, not for use directly on the machine

can you explain how you calculate for that 50 teeth can make up to 600rpm on the spindle speed because I don't understand very well

you speak about step generator, it's for why you use a mesa 7i43 card ? The step generator are not made by the hal function ? In fact I believed that I can use directly the optical encoder on the input pin of my // port and that the software make all the work

So if I resume, you use 3 sensor (2 sensor for the two direction and 1 sensor for counter) ?

do you think that you current homemade encoder is enough for good hobbing or not ?

a picture is worth a thousand words, if you are agree, can you send me some pictures in detail about your installation (encoder) I think it's more easy if I try to make the same model for understand and test it

but I can already test with my current big sensor, for do simple, what I must do for recognize the sensor in emc2 and test them ?

I mean, for me if your spindle move with x degree, your encoder can't move with exactly the same degree because it's depending of the resolution, so I don't see how the synchronism can be perfect and make good hobbing.

yes I had not thought, so in the principe, I can use encoder with just 2 position (half with a teeth and half with nothing) and interpolation can simulate the speed by rpm ?

I just check about my sensor but I think it's not possible to use directly because, Voltage are minimum 10VCC
I try with connect pin with 5V but I don't see anything

I look in hal configuration > pin > stepgen > 0, 1 and 2 categorie and on watch categorie but nothing happen