Can't get Laser On signal to function properly

Machine: Custom design and build, testing Laserboard out of machine

Board: Cohesion3d Laserboard

Firmware: GRBL-LPC

Problem/ Question: not reading continuity across Laser Fire and Laser Ground pins when testing laser on commands

I followed Laser not firing - new laserboard

I’ve tested a few M3 S levels (0, 100, 200, 255)

With my multimeter on continuity mode the meter doesn’t read continuity at any setting but starts to read lower resistance down to 98 ohms at S255 (S0 and S100 read open, S200 reads 415 ohms, and S255 reads 98 ohms)

The laser on LED on the board does turn on with S1 and up but it isn’t a logic on/off setting and instead changes brightness with S level.

Hi Rob.

Please provide pictures of your board, machine, and wiring.

Here’s the current test setup. My machine currently has a TinyG controller in it and I’m wanting to test all the Laserboard outputs I need before installing it (laser on signal, pwm intensity signal, air assist). I’m using a cloud ray laser psu so I can trigger on high or low.

When I test the opto output as you are set up for there, I don’t get full continuity with a meter, I just get some vague numbers on the screen, but the fact that they exist is a good thing.

If you have issues firing when you hook up to TL and Gnd on the LPSU, that’s a different story.

Thanks for the response, I was worried when I checked that other thread that there might be something wrong with the board. I’ll play around more with the setup and will update here.

So we have the 3.3v signal coming out of the microcontroller, then it goes through a 5v level shifter. That output from the level shifter drives the red status LED, the “Alternate PWM out” header, the opto for L and GND that you are tapping into, and a mosfet for driving a diode.

The factory currently has instructions to observe the red LED turning on at the varying brightnesses but they have not been testing the output of the opto. We have had 2 instances of issues with the opto out of something like 400-450 of the new boards shipped since launch in December.

I think we will add some additional tests to verify the opto is good when we run the next batch of boards.

Tested the board in the laser and was able to get the laser firing no issues. ran the laser ground and laser fire to the laser PSU header ground and trigger low pins, grounded the water cooling pin, and used a pot between the laser PSU header 5V, intensity, and gnd pins.

Thanks for the info.