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  1. #1
    Join Date
    Mar 2021
    Posts
    6

    TTL/PWM Output for Laser

    Hey guys, I need some help. I have a NewCNC Series 1 router that I am trying to add a 15W Optlaser to. I am pretty new to CNC machining so please excuse any shortcomings in my description of the issue. In order to function the laser, I need to provide a TLL/ PWM signal and a ground. I have a USS Smoothstepper that connects via port 1 to a PDMX-122 BoB and have open output pins available (15,16,17) on the BoB.

    I have connected the TTL lead of my laser adapter to Pin 16 and made the following adjustments to Mach3:

    Spindle Setup: Checked used spindle motor output - Checked PWM control - PWM base frequency = 5000 - Minimum PWM = 0
    Motor Outputs: Spindle enabled - Step Pin = 16 - Dir Pin =17 (I had to assign 17 a Dir pin as Mach would not let me leave the Dir pin unassigned) DirLowActive = X - StepLowActive = X - Step port = 1 - Dir port = 1
    Pulley Selection: Pulley number 4 - MIn speed = 0 - Max Speed = 10000 - Ratio = 1
    Motor Tuning Spindle: Steps per = 1 - Velocity = 10000 - Acceleration = 2000 - Step pulse = 5 - Dir Pulse = 5

    I also made the following changes in my Smoothstepper config:

    Spindle: Checked PWM, and set base Hz to 5000

    I then created a simple test text file to run using the postprocessor that the laser mfg. provided. I looked into the code on this and it basically removes any Z commands and replaces them with M3 and M5 to turn the laser of and on when rapid move is required. I then ran the program and had two issues. My spindle operated at the same time as the laser, and the laser never powered up enough to make any burns or markings on the plywood sample piece I had on my bed. The motion all worked as expected in X/Y with no Z movement so the issue seems to be with powering up the laser. I checked voltage at the pin of my BoB when running the program expecting to see 0-5 volts but had no reading. I am thinking I am not getting a PWM signal to my output pin on the BoB. Any ideas on what I need to change or that I might have missed would be greatly appreciated!

  2. #2
    Join Date
    Mar 2021
    Posts
    6

    Re: TTL/PWM Output for Laser

    Okay so I have an update. I have continued to work through my Mach3 settings and after adjusting my Spindle relay to Output 4 CW and Output 4 CCW from Output 1CW and 1CCW (Output 4 is not enabled and has no pin assignments) my spindle no longer comes on when I run my test program intended for my laser. I disconnected my laser TTL input line and manually issued an M3 command the led lit at pin 16 and I measured 3.94v at the pin. I am getting a spindle signal, problem solved right....

    Wrong....when I issued an M5 command to shut off the power at pin 16 there was no response. I had to use the E-Stop to shut down the signal. When I went to try turning it back on with another M3 command, nothing this time, it would not turn back on. So I went back into my ports and pins settings looked everything over clicked my Spindle enable button off and back on again and tried the M3 command and I had power at pin 16 again, issued an M5 and the exact same thing happens. I tried setting my Spindle step pin to pin 17 and 14 and had the same result play out on those pins as well.

    I decided to reset everything and hook back up my laser to pin 16 to run a test program. The pin 16 voltage indicator led lit up and the laser was cutting, and like the test commands I put into MDI, the M5 commands in the G-code scrolled by without shutting off the laser, and at the end of the run I had to use the E-stop to power down the laser. When I checked my test engraving, I found that the laser had cut all the way through my 5mm birch sample board. I was running at 10" per min. and 80% power. I feel like to get a cut of that depth the laser had to be running at full power which means I am probably not getting a PMW signal on that pin as well even though I feel I have all of the settings adjusted accordingly. Any ideas on what could be causing these issues?

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