Advanced Search

Thank you for your pointers in the right direction. Helps a lot.

Unfortunately the 7i84 still does not report back. I just discovered that jumper w4 needs to be removed, even though it's not mentioned anywhere. I've been running a simple half file and use your suggested mesaflash prompt to check available serial devices. Is there something else I can do?

loadrt hostmot2
loadrt hm2_pci config=sserial_port_0=000xxxxx

loadrt threads name1=servo-thread period=1000000

addf hm2_5i25.0.read servo-thread
addf hm2_5i25.0.write servo-thread
addf hm2_5i25.0.pet_watchdog servo-thread

start

For axample:
Aluminium extrusion profile L=1200mm (2.9 kg) vs aluminium 50x50x2 tube L=1200mm (3.6kg)

I must say that the weight comparison seems very counter intuitive.

[edit]

you are comparing aluminium extrusion profile to  50x50x2 steel tubing (8000kg/m3).

The most likely problem is that you have 'anglejog.current-scale' = '0'.

Note that the 'anglejog.scale-in' value is only sampled when 'anglejog.enable-in' is false. (See 'Notes' in the man page linked above)

You may want to have a look at the anglejog sim config :
configs/sim/axis/anglejog

 

Thanks, well spotted! I was hoping that 1/3200 microstepping would work.
Perhaps I will have to do a 1/3 reduction later. For now I think I'll try how this works.

The goal is to get linuxcnc up and running first and try to configure everything properly



The point of the 80x40 extrusion profile I certainly do not agree with as a mechanical engineer.
The 80/40 extrusion profile has a much higher stiffness compared to a normal tube. Especially compared to an aluminum tube.

For axample:
Aluminium extrusion profile L=1200mm (2.9 kg) vs aluminium 50x50x2 tube L=1200mm (3.6kg)

Comparison of Bending Resistance
ProfileDirection (axis)                                        Section Modulus (W) 

80x40 extrusion
Major axis (80 mm high) → bending about        X = 8,898,884 mm³ 
Minor axis (40 mm high) → bending about        Y = 120,303 mm³

50x50x2 mm box
Any axis (symmetric) → c = 25 mm                    X and Y = 5,912 mm³

Key Differences:

In the x-axis, the 80x40 profile has ~1500× higher section modulus (1500x stronger!) and is 20% less heavy than the 50x50x2 box.

In the y-axis, it still has ~20× higher section modulus (20x stronger!).

Agreed on the gear reduction or machining a smaller pulley. I think they make htd in 3mm pitch so you can reduce pulley size.

The goal with plasma is to accelerate as fast as possible to the desired cutting speed to minimize slag...... That's basically the entire goal..... The less time you are in-between stopping and cut speed the less slag you will have. So keep all motion components as light and strong as possible. That 80/20 t slot extrusion is heavy and weak (for the weight), use square tube instead.

Also 3d printed parts are fine for a prototype/hobby machine but you are building a machine that shoots sparks everywhere and makes things very hot. Plan for machining the parts out of AL if you want to use it in an industrial environment.

Hope that helps

A guess:

setp hal_gpio.pin-40-out-invert true

Running LinuxCNC and then running:

halcmd show all | grep invert

in a terminal window should give the the exact naming syntax

 

1 No double posting
2 most VFD's can do 0-5V or 0-10V settable, see manual
3 to invert pins on LinuxCNC it is as simple as :Should be similar for RPI, but i do not use RPI so no way of confirming from my side, give it a try.

Hello everyone,

I'm setting up a PWM-controlled spindle for my LinuxCNC machine. My analog DC motor controller requires a 0-10V input, which I'm generating with this specific PWM-to-analog converter: www.amazon.co.uk/Digital-Analog-Module-C...&smid=A2BXCFIGGD7VDT.

The PWM signal is sourced directly from a Raspberry Pi 5's GPIO, routed through our custom-designed isolator board HAT, V1.1, which you can find details about here: github.com/data124001/Isolation/wiki. We're running LinuxCNC version 2.9.1 and using the hal_gpio library.

The core issue is that this specific PWM-to-analog converter appears to invert the control signal: a 100% PWM duty cycle from the Pi (and hal_gpio) results in zero motor speed, while a 0% PWM duty cycle results in full motor speed. This means my spindle speed control is completely reversed from what's expected (higher LinuxCNC speed command = lower motor RPM).

We have confirmed that the PWM signal generated by the Raspberry Pi 5's GPIO (whether directly or via our custom isolator board) is behaving correctly in terms of duty cycle interpretation (e.g., 50% duty cycle is "half on"). However, without this specific PWM-to-analog converter in the loop, we have no meaningful 0-10V speed control for the motor controller, only basic on/off, as the raw PWM is unsuitable.

Therefore, the problem lies squarely with the inversion introduced by the Amazon PWM-to-analog converter itself when converting the standard Pi PWM.

My question is: What are the most effective and robust methods within LinuxCNC's HAL configuration to invert the hal_gpio PWM signal before it reaches this converter? I'm looking for a HAL-based software solution to achieve the correct 0-10V spindle speed control (where a higher LinuxCNC spindle.0.speed-out value corresponds to a higher analog voltage to the motor controller and thus higher motor RPM).

I will be attaching my HAL and INI files to this post to provide full context of my current setup.

Any specific HAL configurations or example code would be incredibly helpful!

Thanks in advance.