New install with older board, laser either always on full or not firing

Machine: ebay K40 with M2Nano originally

Board: cohesion3d mini v2.2

Firmware: Smoothie “Its a new board as have had it waiting to install for years! and I’m using whatever it came with”

Problem/ Question:

I have installed the board and am having issues with the laser firing, the movement works great and have tweeked the settings to get this smooth.

Using lightburn when i run a job it puts the laser to full power every time even with power set at lower levels such as 4% etc. It is on even when moving between cuts…

I suspected the PWM period so have tried 200 and 400 but this makes no difference, so i then moved onto testing with the PWM tuning guide here:

running the following moves the gantry but no laser fire…

  1. G21
  2. G0 X0 Z0
  3. G0 X0 Y10
  4. G1 X300 S0.8 F600

So i am confused as to what i have done wrong here, could someone lend a hand and help me out!?

I have attached pics of my setup.

Thanks in advance all!!!

Snippet of GCode from Lightburn used to test,this turns the laser on full always even during the move to first position:

; LightBurn 0.9.11
; Smoothieware device profile, absolute coords
G00 G17 G40 G21 G54
; Scan+Cut @ 100 mm/sec, 4% power

Can you post some pictures of your board and the wiring going into it? (oops, missed the edit with the pic of the board added)

I fixed the first pic in his post by making sure there was a ! in front of the image upload string.

Hi Craig,

I can’t find your name in our order records (which could be due to a number of reasons), but if you say it is a Mini v2.2 then I think you might have one of the very first boards we made in the end of 2016.

Here is some info that will help. To anyone else reading this, please do not follow the instructions below unless you have confirmed with a C3D staff member that they apply to you. These are special considerations for hardware that is 4 years old.

You can find the links to the C3D Mini resources linked here:

We’ve changed websites and documentation platforms a number of times and are focusing on our new board now (the Mini was discontinued a bit over a year ago), but the old docs are still up on the Freshdesk platform linked from that old getting started page.

Note that on the early Mini boards there was a “PWM cable” included but we quickly stopped using that.

The software we are using nowadays is LightBurn, which is amazing:

My staff and I will help as best we can on the forum (here):

The main things to keep in mind:

Grab the latest sd card files from a dropbox link at the bottom of the install guide. Your board corresponds to a batch 2 board with regard to the config file, but you can use batch 3 files, just know that we changed the screen buzzer pin so you may have a constantly on buzzer if the screen is connected until you change that pin number.

You’ll also need to disconnect the L wire from the large power plug and connect it to this screw terminal #4 instead:

ALSO VERY IMPORTANT: Completely isolate the board from the metal frame with nylon spacers or an acrylic plate or whatever.

Get a separate 24v power supply to power the board. The LPSU 24v rail is very shoddy.

These things are covered in the various guides on the getting-started-old page. Make sure you read them.

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Hi Ray,

Wow that was a quick response, Thanks!

I had been using the freshdesk info for older boards but had followed the guide matching my psu as it has the 4 pin molex connector.

Guide i used is here:

So are you saying I need to break that apart and follow the image in the post?

Out of curiosity, how come this is different on this board as it still has the k40 molex connector socket on it?

On the isolation, do i need the screws isolated as the board is raised on nylon spacers?

Thanks again!!


Well, the other guys here weren’t around 5 years ago, or inside my head (thankfully for them), so I figured it was best to jump in and save everyone some frustration. I “conveniently” had to write all that up for someone else last month over email, so all it took was some simple copy paste and removal of expletives :slight_smile:

Try to follow this train of logic:

  1. You have a Mini, the docs are on the getting-started-old site.

  2. You appear to have a very first batch Mini (first 100 we ever made) where we did things a little differently regarding the L laser control mechanism, so you need to then follow the override instructions I have presented to you - the part about relocating the green wire from the plug to the screw terminal.

  3. Then, if you follow the separate power supply guide also linked on getting-started-old, that’s where the red and black wires going to the other screw terminal would end up. Now the large white plug is could be completely unneeded.

We had a different way of controlling the laser firing (2 wires instead of one, potentiometer was removed from the equation, test fire button rendered useless), which quickly got changed after the first 100 boards. This is why the white JST cable is no longer needed. It is a different signal that is connected to the L fire pin of the large connector on those first boards, one that is not capable of PWM. So you have to move it to the screw terminal to get the L wire to the proper control signal.

Yes, it’s covered in the install guide you linked.

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