Laser Head Height Sensor – Looking for a Beta Tester

Well this is exciting. I have a bit of machining to do to get this mounted on a ball screw for further testing. Hopefully tomorrow
 

Lukasz at Proma is very impatient!  

I also built a laser cutting machine based on Linux, I just need a high-precision and fast height sensor. The height needs to be controlled in the range of 0.4 - 25 mm. Do you have a closed project? I wonder what element base it is implemented on? I tried to use ad7745, but it did not show itself very well. I want EtherCAT as an interface.

The sensor is a product is from Proma Elecktronica in Poland. I am helping him to test it with Linuxcnc. The idea Proma had was to make a sensor that was easy to use for DIY projects.

I am writing a component to help integrate this into Linuxcnc. I have not even checked this will compile yet but its a start
github.com/rodw-au/proma-cv2
The idea I had was to do a fast calibration whenever the Z axis is homed.

stkvit wrote:

I also built a laser cutting machine based on Linux, I just need a high-precision and fast height sensor. The height needs to be controlled in the range of 0.4 - 25 mm. Do you have a closed project? I wonder what element base it is implemented on? I tried to use ad7745, but it did not show itself very well. I want EtherCAT as an interface.

My project is closed and will be a complete set with my new control system (purely commercial project).

However, I decided to adapt it in a way that it could also be used by other standard systems.

I will reveal the details that I found out on my own and were hard to find on the Internet:

As for AD7745/AD7746, I tried to use it as a controller for gas burners. It was not easy because it worked on the desk, but during cutting, the gas changed the parameters very much and the AD7745/AD7746 measurement method was not suitable.

1. It is not suitable for lasers because the reading is too slow 90Hz.

To make sense for Lasers, the absolute minimum sampling is 500Hz (2ms), I have 3650Hz sampling but I do not want/cannot reveal why this value is chosen and it should be selected for a specific type of processing.
2. AD7745/AD7746 have a measurement range of 17pF (60pF tollerant), which is definitely too little because the parasitic capacitances on the wire, head, etc. are 50-200pF
3. The useful measurement range of the distance is 0.1pF - 30pF, although for some types of nozzles the range may be wider
4. I chose the method of measuring the capacitance charging time, although I also experimented with measuring the frequency as in BCL-AMP + BCS, which was a bit less stable but also very good.
5. Unfortunately, I did not find any ready-made circuit like AD7745/AD7746 that would be suitable, and I had to design everything from scratch.

If you want to use my sensor for 0-25mm, it is possible to use it in MODE 0 (C2V 0-10V) which converts capacitance directly to voltage (it is not calibrated/scaled to a height of 10mm). However, it is very non-linear and as mentioned in the user manual, for such large distances the reading may be inaccurate and unstable. This results from points 2, 3 because at a height of 25mm the share of specific to parasitic capacitance is about 0.1 - 0.2%, which is not easy to read.

proma-elektronika.com/download/c2v_laser_sense_en.pdf

stkvit wrote:

I want EtherCAT as an interface.

I forgot to mention I am planning to use Ethercat too. A Beckhoff 5151 encoder interface arrived today. I also have a THCAD10 here which may allow reading of 0-10 volt using it. I will use a Beckhoff 2502 for PWM signal for laser.

very sad, i use linuxcnc for open-source, i like to develop my devices, as 99% of linuxcnc users. what is the price of your device?

stkvit wrote:

very sad, i use linuxcnc for open-source, i like to develop my devices, as 99% of linuxcnc users. what is the price of your device?

As I mentioned, this device was developed as part of my commercial control system, which is my source of income—it is purely a commercial endeavor (I make a living from designing and producing these devices). It operates similarly to other commercial solutions, such as MESA controllers. However, I am working on adapting the device to also be compatible with open-source projects, such as the excellent LinuxCNC.As for the price, it has not been precisely determined yet, as the project has been evolving for a long time and continues to change. In fact, I am not even 100% certain it will reach the market, as this is one of the most challenging projects I have worked on, and I am encountering many difficulties.If everything goes well, the initial promotional price is estimated to be $199 USD.

Rod wrote :  Lukasz at Proma is very impatient!  

that's not true Rod , I'm an extremely patient person.
The fact that the shipment arrived quickly has nothing to do with it.

However, I must admit that I am very curious about the first attempts with LinuxCNC.

I would be happy to buy your sensor, but delivery to our country does not work. If possible, share basic information about your developments (source code is not needed), this is very interesting and can motivate many to develop their own sensors. From simple ideas, study the BCL-AMP circuit and create on one board together with a fast microcontroller (like on BCS100) and EtherCAT on LAN9252.