Author Topic: PMDX-424 PWM control for Laser  (Read 2165 times)

trippank

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PMDX-424 PWM control for Laser
« on: February 15, 2020, 03:07:07 PM »
I have been using my 424 on my CNC for about a year now.  I am trying to add a laser.  The 7w laser has red, black, yellow.  Red and Black are for 12v and the yellow is PWM.

I clone my Mach4 profile and created a laser profile so not to mess with router profile

Can the 424 control the pwm thru output 1 without a breakout board?  If so, what are the correct settings in Mach4 and the plugin?

I have Mach4 spindle 0 min 0 max 100 feedback 1.00
on the plugin I have selected Spindle - pwm Output 1 and told it to report Estimate RPM from pwm/pulse frequency.


I measure with a meter on the 424 output 1 voltage is almost 5V.  It doesn't change at all when I slide the spindle speed up or down.  And on the machine diagnostic window, it shows 0 true rpm no matter where the slider is.

I feel like I have missed something in the Mach4 setup not telling the PDMX-424 to control spindle. (Perhaps on the output signals tab)


What else do I need to do? 
Many Thanks
Tripp

12strings

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Re: PMDX-424 PWM control for Laser
« Reply #1 on: February 15, 2020, 10:47:51 PM »
I think that should be all you need (i.e. the plug-in's spindle config tab).  You do not need to configure anything in the normal Configure->Control, "Output Signals" tab for the PWM to work.

To ask a silly question - are you turning on the spindle before you try moving the slider?  And what slider are you using?  In the standard wx4 screen set, the slider in the lower right corner of the screen, just below the "SRO%" text, is "spindle rate override", not directly spindle speed.  It takes the currently commanded spindle speed and multiplies it by the percentage shown.  But you still have to enable the PWM (M3 command or click the "Spindlw CW" button), and command it to a speed (using an "S" command in the MDI window).
 

trippank

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Re: PMDX-424 PWM control for Laser
« Reply #2 on: February 17, 2020, 09:29:34 AM »
12strings.  Thank you for your reply.  I am turning on the laser with the Spindle CW button.  AND I was using the slider overide incorrectly as you guesses.  I hadn't set a speed yet.  Guess I need to get more hands on with Gcode.
So after starting SpindleCW and setting Speed (S50) via MDI, the slider "overrides" and is reporting back the speed accordingly.  Thank you
I also confirmed with a Volt meter it is modulating properly.  However, the laser seems to be at 100% no mater what the speed it set to

Another question, read below from the Laser Seller.  I know his English is bad, its about the pwm frequency I have  question

"When you connect laser to your controller board, please pay attention to the pin positions of 12v+ GND- and PWM/TTL, red wire=12V+, black wire=GND-. Yello wire=PWM+, white wire=PWM-(3-4pin wire). So Red Wire must be connected to the 12v+ pin on your controller board’s interface, Black Wire Must be connected to the GND- pin and Yellow Wire must be connected to the PWM/TTL pin, if you use 3-4pin wire, White wire should be connected to the PWM- pin.
if your controller board’s laser interface pins are in different position, please change the wires position to make it match the positions of + - PWM of your interface. If the wires connected wrong, it will damage the diode and the driver board.
Frequency: <15khz, PWM/TTL: 0-5V"

So, my laser has three wires, red (12v), black (neg) and Yellow (PWM).  have the yellow set to output 1 on 424.  It looks like the pwm frequency only goes up to 1000 Hz on the plug in which should be fine since he says <15khz.  It just seems like the laser is ignoring the pwm.

Any suggestions?  Tripp

12strings

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Re: PMDX-424 PWM control for Laser
« Reply #3 on: February 17, 2020, 10:03:50 PM »
Where are you getting the 12V for the laser?  Do you have the GND for your laser 12V supply connected to the LGND on the PMDX-424 J12?  Do not connect the laser 12V GND to the "GND" pins on PMDX-424 J16 or J17 - those are isolated inputs and the GND there is NOT connected to the LGND that is the ground reference for the output signals on J12 (or the NON-isolated input signals on J13).

So your laser wiring should be:
Red - to your (I presume) external 12V supply's V+ terminal
Black - to your external 12V supply's GND terminal *AND* PMDX-424 J12 pin 5 ("LGND")
Yellow - to PMDX-424 J12 pin 2 (labeled "1")

trippank

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Re: PMDX-424 PWM control for Laser
« Reply #4 on: February 24, 2020, 09:41:01 PM »
You are correct that I have a separate 12VDC 5amp power supply. My wiring is as follows

Red - to external 12V supply's V+ terminal
Black - to your external 12V supply's GND terminal
Yellow - to PMDX-424 J12 pin 2 (labeled "Output 1")

In the pics you can see I am getting 5V on the yellow IN REF TO the ground you are calling " PMDX-424 J12 pin 5 ("LGND")" . I was wondering how they were grounding the PWM.
I will go back and tie the external 12v power supply GND to the Ground pin on J12.  I guess I was scared hooking up a powerful power supply to the 424 output GND,

Just to make sure I have attached a wiring diagram I am using and have marked your suggestion in RED. I am just worried about hooking 12v GND to the output GND.

I won't be able to try this until Friday night when I get back to the shop.  When I was measuring the yellow wire voltage in ref to J12 GND, i was getting 5V at 100%, 2.5 at 50%, 0.5 at 10%  So the board output1 is correct.

12strings, thank you very much for your input .  Very clear, very knowledgeable and welcoming.

Tripp

12strings

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Re: PMDX-424 PWM control for Laser
« Reply #5 on: February 25, 2020, 12:28:26 AM »
Yep - that connection from the 12V GND to the PDMX-424 "LGND" (on J12) should do the trick.