2.x Laser Build, LPS output will not turn off after the cmd to turn on is sent.

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27 Feb 2017 23:49 #88713 by punitor1
Hello,

This is regarding a non-standard 2.x Linux CNC build using a real time BOB.

I just upgraded my 3 year old home built laser with a new 130watt tube and power supply. My old system used low level PWM control but I decided to switch to high level during the upgrade (always wanted to make it fail safe to avoid flashing the laser if the system was not started in proper order).

I removed the "invert" command from the laser fire pin in the .hal file and adjusted the max PWM output to correspond with the max safe level for the new tube.

The laser fires great (turned a fired brick into glass), everything is working well - except after the fire comand (M3 or M4, tried both) in any gcode file is run the laser power supply does not go into standby - including when using the test fire option within 2.x GUI (146.ngc) it just keeps firing. Thankfully I have a emergency "laser off" switch that interrupts the coolant verification signal and shuts it down properly.

I worked on this all day, I tried everything I could think of but have not figured it out yet. I don't have a good o-scope to check the BOB signal with, so I don't think there is a way to eliminate the possibility of a hardware or wiring issue?

I think it must be in the 2.x laser .hal file but I cannot find it.
The only other option is that the new power supply has a grounding issue that is allowing some stray voltage to trigger the laser but this would be odd since the laser power level is consistent at my 25mA set point.

Any ideas?

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28 Feb 2017 14:01 #88728 by andypugh
I think we would need a little more detail about how the system works, and the HAL file to inspect.

Does the HAL file set a minimum duty-cycle for the PWM? Does the HAL file disable the PWM when the "spindle" is off?

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28 Feb 2017 14:59 #88735 by punitor1
Hi Andy,

I have attached the .hal file, a test fire file created by my dxf-gcode converter and the 2.x laser test fire file 146.ngc

I don't know how I did not see it before but the "Power" bar indicator on the right hand side of the 2.x laser screen comes on and stays on whenever a gcode file is run - any file. I use PWM (or PDM) - not "Power" and the PWM bar and indicators on the 2.x screen do fire properly per the gcode files. This is the problem but I cannot figure out where the "Power" command is being issued from.

File Attachment:

File Name: 2x_Laser.hal
File Size:7 KB

File Attachment:

File Name: 146.ngc
File Size:0 KB

File Attachment:

File Name: On-Offtest.ngc
File Size:1 KB


Thanks,
Travis
Attachments:

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28 Feb 2017 15:23 - 28 Feb 2017 15:23 #88739 by andypugh
Is the laser pwm pin connected to parport pin 07 (laser-final) or parport pin 06 (laser-pwm) ?

If the latter, then it looks like almost none of that is being used, and this line is what controls the laser:

net laser-power-cmd <= motion.analog-out-00 => pwmgen.0.value

motion.analog-out-00 is controlled by G-code, this particular line in the sample file
M68 E0 Q100
linuxcnc.org/docs/2.7/html/gcode/m-code.html#mcode:m68
Last edit: 28 Feb 2017 15:23 by andypugh.

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28 Feb 2017 18:54 #88759 by punitor1
Thank you Andy, that led me in the right direction. It is pin 7 and we have reconfigured the .hal file accordingly - updated attached along with .ini. I still need to adjust my gcode converter. I am getting a low level signal (results in 5mA) at all times (even before running a file) with the new configuration, it is just enough to start the tube, any idea how to adjust the low level signal out? I thought I was already at 0.0 in .hal, am I not? I am reading 1.31vdc on pin 7 when idle. After running a file the LPS remains on at about 15mA - although this could easily be the gcode test file which still needs to be reconfigured.

File Attachment:

File Name: 2x_Laser_2...2-28.hal
File Size:7 KB

File Attachment:

File Name: 2x_Laser.ini
File Size:3 KB
Attachments:

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28 Feb 2017 19:16 #88761 by punitor1
The 1.31vdc is a wiring issue - it is present even without emc running. I imagine it has always been their and I never knew - since I had been using a low level trigger. I am working on it.

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28 Feb 2017 20:29 - 28 Feb 2017 20:30 #88775 by punitor1
Most of the stray voltage is coming in over the parallel port cable - strange since my BOB (V_5 from LightObject) is supposed to be optically isolated. The parallel port cable shield does not test common with the PC or with the any of the CNC DC-. I tried grounding out the shield to eliminate the possibility of inductive current from the bundle of cables but it had no effect. In the hope of using a shortcut I also tried switching back to low level pwm, but it still triggers the laser (at 18mA this time) - proving that this is likely a new problem. I have not made any significant wiring changes with the new power supply - I did switch from a 110vac LPS to a 220vac LPS - for increased stability with the higher wattage laser and I changed out the coolant flow switch for a new one while adding a PID temp controlled relay in series with the coolant flow switch - for a coolant flow and high temp failsafe.

I am considering adding a jumper from my DC Negative buss to AC Earth Ground, I stopped short of doing this when I first built the laser because I did not want to create a earth ground path through the DC circuits in case of a high voltage leak from the LPS - no need to blow everything up, especially since the LPS, DC supply cases and whole machine case are earth grounded. Is this flawed logic? I tried a temporary jumper with the LPS disconnected with no change on pin 7.

I think I am back to the .hal setup at this point and trying to lower the minimum voltage on pin 7. Any ideas?
Last edit: 28 Feb 2017 20:30 by punitor1.

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28 Feb 2017 21:24 #88781 by andypugh

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28 Feb 2017 21:39 #88782 by punitor1
I have an ancient heathkit with crt display (mad scientest special), but I don't think it works anymore and I doubt I could remember how to operate it.

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28 Feb 2017 22:15 #88784 by punitor1
I do have a 40kHz meter on my fluke multimeter. I just checked pin 7 to LPS DC ground. With emc in standby (or off) the fluke reads OL (overload). with the test file running the fluke reads 11.06kHz.

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