Laser Head Height Sensor – Looking for a Beta Tester

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27 Feb 2025 12:58 - 27 Feb 2025 13:03 #322786 by prokopcio
Hello everyone!I have completed the design of a laser head height sensor. While it was originally developed for systems other than LinuxCNC,
I would like to extend its compatibility to this popular and highly capable control system.Is there anyone here who could help me/ be a beta tester? I have no experience with LinuxCNC.Available output configurations:
  • Direct processing: capacitance/voltage 0-10V (nonlinear)
  • Linear processing: 0-10mm → 0-10V (reversible)
  • Linear processing: 0-5mm → 0-10V (reversible)
  • USART 57600, 0.00-10.00mm with 0.01mm resolution
If another configuration is needed, I can adapt it.I would be happy to send the device for testing with a laser head + LinuxCNC.
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Last edit: 27 Feb 2025 13:03 by prokopcio.
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27 Feb 2025 16:35 #322800 by rodw
If you get stuck, I am in Australia and have a 500W laser head I need to buy a BCL-AMP for.

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27 Feb 2025 17:35 #322803 by prokopcio
Thank you but if you have a system adapted for the standard BCL-AMP and you measure frequency, my device is not adapted for this.

The output signal of my converter is an analog signal 0-10V or digital serial transmission (USART).
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27 Feb 2025 20:43 #322818 by rodw
No, the system will be linuxcnc, the head does not yet  have a BC-AMP but there is provision to mount an amplifier to existing tapped holes. So at this stage I don't measure anything!
 
Your unit should fit and it would be up to me to adapt  linuxcnc to read your system and interpret the results for height control.
I have previously beta tested some hardware for Mesa and developed an ohmic sensing component for linuxcnc, which is now part of linuxcnc that enables the hardware I tested.
linuxcnc.org/docs/stable/html/man/man9/ohmic.9.html


 
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27 Feb 2025 21:33 #322824 by tommylight
Send one to Rod, her can make it work easily as he has THCAD that turn 0-10V to frequency, and he is very detailed when testing stuff.
I do not have a laser (i do have a big box of lasers, but He-Ne ones at low power) so i can not help with testing it. I can attach it to a plasma torch and see how long it lasts with all the interference plasma causes, but that is it. Oh yeah, Rod can also test this, as he has plasma machines.
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28 Feb 2025 08:34 #322856 by prokopcio
fantastic.

There is still a possibility of implementation, so I would like to adapt it to LinuxCNC as much as possible.

I am not sure if it makes practical sense to process data multiple times, which loses measurement accuracy and introduces additional errors at each stage C/f -> U -> f ...

i can made frequency output directly in sensor.

I see that the THCAD5 card processes voltage to frequencies in the range of 100 kHz - 1 MHz, but I can adapt to any frequency (lower frexuancy could be directly monitored in many "less efficient" controllers and send via cable easyer ), it can also be a PWM output or serial communication, which I can send a ready-to-use height without the need for the CNC system to process the signal, which in my opinion would be the best option.

In your opinion, what would be the best option?

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28 Feb 2025 09:39 #322860 by rodw
 Great! Let's move ahead.

Let's talk about 0-10 volt range first.
The Mesa THCAD is a voltage to frequency converter. The THCAD10 has a 10 volt full scale. The THCAD 5 has a 5 volt full scale. The newer THCAD2 can be configured to either have a 10v or 5v full scale range. For your hardware, the 10v range sounds best.
We read the frequency using an encoder A input (usually on a Mesa card) and then scale it internally back to a voltage. Usually we set the THCAD's on board frequency divider so we read 1/32 of the frequency when sending it to Linuxcnc.

To receive a frequency, we would simply connect your hardware direct to an encoder A input and not use a THCAD.

It would be easy to apply a mathematical function to the encoder frequency to convert to a voltage in a real time component written in C.

There are other options to read both voltage and frequency. For example, appropriate Ethercat slaves for both voltage and frequency are available.
I think for Ethercat I would prefer 0-10 volt.

Finally, I might mention that for plasma torch height control, we adjust the height using external offsets (this offset is external to the motion controller). A scaled count (much like a MPG) allows us to take the input and output a height adjustment of the error. But because you output a distance, it might be possible to manage height control via one of Linuxcnc's PIDS.
 
Anyway, if you have a contact us option on your website, let me know, and I will reach out to take things further.
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28 Feb 2025 10:26 #322862 by prokopcio
of course, the 0-10V output voltage is the standard output, regardless of the others I want to input.

I am "internally hurt" by multiple signal processing, so I suggested that I also output a frequency signal that can be connected directly to the encoder input. or send it via any serial port / UART.

but ok. let's start with the basic 0-10V.
unfortunately I do not foresee an upgrade option for the end user, so I have to program everything before shipping.

But I see no problem in sending new versions.

for details you can contact me directly.

proma-elektronika.com/contact/

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28 Feb 2025 11:31 #322863 by rodw
Thanks, I sent a message.

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28 Feb 2025 15:29 #322872 by PCW
I would think a direct frequency output would be desirable as its readable
in real time by many different types of interface hardware.
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