Centroid Community CNC Support Forum

Hi all
I have previously built a CNC lathe using Centroid Acorn. Now I am building a CNC router and plan to integrate a laser engraving machine into this CNC router.

I have followed the Centroid manual and web documentation, but I am facing a problem: I am not getting a PWM pulse; it stays at 0 V. I have set the PWM settings in Acorn Wizard. A simple oscilloscope was connected to pin 14 of the DB25 port and GND. Even with this setting, when I enter a command like "M3S0 G37 OFF M37 M3S1000" from MDI, it remains at 0V. Is my Acorn board faulty? By the way, I tried the same thing with the centroid acorn I use on my lathe, and I got a PWM pulse.

Please let me know if there is anything else I should do. Sorry for my poor English.

Did you cut the 3rd wire to the Output relay board?

https://www.centroidcnc.com/centroid_di ... _laser.pdf

Uwe

I have already cut the third wire that connects to relay 2.

The Acorn board's OUTPUT LED lights green when set to S1000, and a mixture of red and green when set to S500. I don't know if this is normal operation, but the PWM signal itself seems to be generated from the main board. However, pin 14 of the DB25 port does not seem to have a 5V output. I'm wondering if something like a damaged pull-up resistor, pull-down resistor, or transistor is causing the 5V output to stop working. Is there a way to check that?

Are you using a breakout board or are you reading the signal directly at pin14 on the Acorn?
You can check the ability of Pin14 to output 5V by setting PWM Enable to "No" in the PWM Setup screen.
Set PWM Enable to "No" in the wizard and save the settings. Pin 14 should now be at 5VDC when OUT2 is off.

Thanks for the reply.
I am reading the signal on pin 14 directly with an oscilloscope probe.
I will try your method.
If this does not work and everything else is working fine, I am assuming that the logic IC called ACT125G, which is connected to the DB25 port, is broken for some reason, but what do you think?

kaira3 wrote: ↑Tue Oct 10, 2023 1:02 am Thanks for the reply.
I am reading the signal on pin 14 directly with an oscilloscope probe.
I will try your method.
If this does not work and everything else is working fine, I am assuming that the logic IC called ACT125G, which is connected to the DB25 port, is broken for some reason, but what do you think?

What were the results of this? Did you see the expected signal?

Sorry for the late response. I tried to do it. But I couldn't detect the expected signal. It seems that my Acorn still has a broken part of the chip. At first I connected the laser engraver to a LT-80W-AA-PRO 24V, which I bought from Aliexpress, but I think this might have possibly over-currented it, because the logic IC called ATC125, which converts the current from the BB to a 5V PWM, is sensitive to over-current. I suspect that is why Centroid has provided a dedicated PWM pin on the new Hickory and Acorn6.

I'm busy at work for a while, so when I'm free I'll try to fix it again and report back. Thanks for your help.　

I finally had time to repair it.
I successfully repaired it by replacing the Buffer IC (ACT125G).

The repair I did is described below, but anyone who imitates it does so at their own risk, don't blame Centroid or me. If you need repairs, use Centroid's repair service.

1.Remove the Beaglebone.
2.Remove IC12 using a heat gun (rework station)
3.Re-solder the ACT125G.

Now I don't know what caused it to break this time. But I'm glad it's fixed anyway. Thanks to those who gave me advice.

wow, ok great, glad you got it going!