This sounds like you have a TTL laser and not a PWM laser.
@alanbabb Interesting. Both the specs online and the laser module say that it is ācompatibleā with both TTL and PWM. I wonder if there is something that I need to do to set it to PWM. It is the same model as the one that Kris and Andy used. I didnāt see anything in their posts that spoke to that.
I couldnāt find any specs on it so I had to assume. The 5W laser I have had a positive lead to power the external controller and its fan and the lasers fan. It has another PWM lead and a Ground. I have the PWM lead and the ground running to the PWM terminals. The power lead goes to the external power positive terminal. I use it for cutting for an industrial application. I am buying another Longmill that will only have a laser on it to put in a factory in Mexico because it works so well. This maybe a silly question but did you turn on the laser mode? Have you also made sure that the max spindle speeds in Lightburn match what is in your controller?
@alanbabb Alan. The laser that I have is the same one that Kris pictured in his post about his installation. It has a power jack +/- for the laser and a power jack +/- for the fans. The wires from them run from the board to the laser module. These are the leads that need to be lengthened.
Then, there is the input power lead that runs from the power brick to the board. Included in that cable is another one-conductor lead marked PWM. Kris did not use this lead, and neither did I. Finally, there is a 2-pin female jack on the board labelled PWM/TTL. Following Krisā advice, this is the one that I used to connect the board to the PWM spindle control on the Long Mill controller.
I am assuming that that final lead is OK since LightBurn sees the grbl controller and the com port that windows has assigned to it.
I can burn with the unit, although I still have not figured out how Lightburn determines X and Y0 for the job. Iāve watched several videos, but I guess that Iām dense.
I did activate the fire option in Lightburn and, in the Move window, I can now see the button to set the fire power. I set it to 10% and the laser still burned wood. I set it to 0%, thinking that should turn the laser off altogether. It did not.
In terms of grbl settings, I have turned on the laser function using $32=1. Kris and Andy say to turn on the max power using $30=100. However, Lightburn says to turn it on using $30=1000. Iām not sure if the considerable difference in those two settings has something to do with the firmware in the Long Mill controller, so I used the 100 set out by Andy and Kris.
Physically, I have the laser positioned about 2.75" above the surface of the piece. Iām thinking that maybe that is too close, and today, if I get time, Iāll play with that.
Iām open to anything else you can suggest.
This is just an update to my previous post.
According to the Lightburn site, controllers running grbl 1.1 or newer can turn off the laser entirely when movement is stopped. Here is the text from their site:
"The more recent versions of Grbl (1.1f and up) support two things that are incredibly useful for lasers. The first is Laser Mode, enabled by setting $32=1 in the firmware settings. Laser mode eliminates the pauses that happen when changing power output, because Grbl knows itās controlling a laser which reacts instantly, instead of waiting for a spindle to change RPM.
The second is a feature called variable power mode, or the M4 command. In this mode, Grbl adjusts the laser power as the machine speeds up and slows down, making for very consistent cutting and marking. Older versions of Grbl do not have this feature, and simply run the laser at a constant power output for the duration of a cut. Since the machine needs to slow down to take sharp corners, this means corners get over-burnt, while long straight lines end up lighter.
This also has the benefit that when the laser comes to a complete stop, the beam turns off (zero speed equals zero power), meaning that pausing a job automatically turns off the laser. This is not always true with other versions of Grbl."
My machine is definitely not doing this. When the machine is not moving, either at the start or end of a job, the laser is burning.
Is the āoffā function actually working for others here?
Lightburn is only connecting to the Longmill controller. The laser is just working from the output of the PWM terminals of the Longmill controller. There is no communication directly from Lightburn to the laser.
Lightburn has to have its maximum spindle speed setting set to match what is in $32. This is how it controls the laser power. What exactly you put in them is not as important as them matching. If you have 3000 in there then 0-3000 gets mapped to 0-100% laser power.
I have the same wiring structure as yours except the extra wire. The extra PWM wire is odd. Maybe try using that instead of the TTL/PWM lead??
Anyone know can you just burn with lightburn or should you load gcode into something else. I havent changed no settings and everything seems to be working in lightburn. I understand I still have to change the $32=1 and $30=100
@Incredz I have very limited experience with Lightburn, Justin, but for one project. I imported a dxf file, then saved the gcode in LB. The next time that I wanted to run the project, I just clicked run gcode. It opened a browser, I chose the file, and it ran it. I donāt know if this answers your question, but thatās all Iāve got. 
@alanbabb Alan: Does the fire function in LB work for you? I set it to 1% and the laser still burns wood. However, I have found that the pwm wire running from the long mill controller to the laser board is doing nothing. Now, all I need to find out is why and how to fix it. Andy is helping me with this. If you have a meter, can you tell me what voltage you are getting from the pwm cable when you are running a job in Lightburn?
The fire button works great on my machine. I typically turn on the laser at 2% to set the focus.
I donāt think you can measure a PWM signal with an ordinary volt meter. I have never tried but I think the switching speed may make that impractical. Maybe if it is set to 100% duty cycle? I believe you may need to look at it on an oscilloscope. I may have my mini one here at the house.
@alanbabb Tks, Alan. Thatās what I was afraid of. I think my laser is defective and since I canāt return it now that the wires are cut, Iām out of luck. Live and learn, I guess.
Just out of curiosity, if you set the fire to 0%, does it turn the laser off?
I have not ever tried that but I will tonight and I will let you know. I will give measuring the PWM output a try with a volt meter and, if my mini oscilloscope is home, on that as well.
For what itās worth, I am using the Sainsmart laser module. It came with the 3018 I bought about 3 weeks before ordering my Longmill. Thatās what got me hooked on this crazy hobby. It works great and I have had no issues with it.
1 Like
Wear did you get a wire for the PWM connection to the long board mine didnāt come with this wire and I canāt find any laser that do our even find the wire to purchase it
Wear did you get a wire for the PWM connection to the long board mine didnāt come with this wire and I canāt find any laser that do our even find the wire to purchase it
@Chrslintz Chris: Mine did not come with that wire, either. In Krisā write up, he says that his didnāt.
I just used a length of 18/2 wire that I had lying around. As for the 2-pin plug at the laser drive board end, I used a male connector from an old computer fan that has been gathering dust for years. I simply cut it off the fan, leaving a few inches of the 2 conductor wire and spliced it to the 18/2 that I had. The green plug on the long mill controller end was already on the controller.
If you also use a computer fan connector, be alert to polarity. The way that my fan connector plugged onto the board meant that black was +. This is the reverse of normal to me. Itās no big deal. It just meant ensuring that the black wire from my 18/2 extension also went to the + terminal on the long mill controller.
Thabo you gwilki for confirming that I was looking to find out if I could use one of those. Now Iām going to go beat my head against the wall because this is about the third time i needed use of one of two old computerās i got rid of shortly before I baught my machine ugh. Thank you for your quick answer
@Chrslintz I know exactly what you mean, Chris. I have piles of this stuff in the basement, and curse every time I need to move it. I swear each time to toss it all. Then, I find a need for some obscure plug and congratulate myself for keeping it.
We no longer have any retail electronic stores locally, so Iām always trying to find things like this in my piles. Frequently, it is cheaper to go to a computer store and buy something like a fan, just to use the plug, than it is to buy the plug.
Have fun.
As an aside,does your laser have a āweakā light button on the board, and if so, does it work. I have the button and it does nothing. Damn!
Ya knowā¦I just scavenged a bunch of plugs and wires from old work PCs: molex. 2, 3 ,4 pin, SATA and stuffā¦just pitched it about a month ago, cuz Iāll never need or use itā¦Doh!
I bought some off of amazon especially since paying for something is better than free, right.
1 Like
Yes it does have that buttonā¦ time for me to hit some yard sales i guess lol
@Chrslintz Chris: To test the button, you donāt need the pwm hooked up. You can just connect the fan and laser wires from the board to the laser, plug the board into the power supply and turn it on. The fans will spin and the laser will fire. Press the button. A red led will flash on the board and the laser will power down so that it does not burn, but shines āweaklyā.
On mine, the red led blinks and the laser is still on full power.
I didnāt think to try this before lengthening the wires, so returning it is a no go.
I strongly suggest that you try this before doing anything else.