Duet wiring K40 laser co2

  • Hello!
    In a group of economic CO2 laser, Blue K40 laser, we want to change the board of our machines and we are considering using duet maestro, since several of us already use duet in our machines.

    I have searched and found contradictory information in the forum, external websites etc ... and I wanted to check the current state of laser development (in one of the last changelog mentioned lightburn software), and the connection to this type of machines.

    There are some people who have migrated it to ramps, they use the servo ports for laser control, 2 pins since one is pwm for power and the other is activation at 5V.

    I will be putting the info I have located on the laser and see if together we can confirm if the change is possible, since the current board does not allow pwm in the gcode, it is controlled from a separate panel that generates the pwm, but not by gcode

    There are people who have changed it with a cohesion3d board, but they are not cheap and they come from the USA, so you have to pay customs. Also, if possible, we prefer to maintain the duet3D ecosystem ; P

    I use a translator, so if any part is not clear, let me know and check it.

    this is schematic for ramps:

    alt text

    Github marlin conversion, with schematic and firmware

    More info for ramps, http://weistekengineering.com/?p=2406

    Other link: http://3dprintzothar.blogspot.com/2014/08/40-watt-chinese-co2-laser-upgrade-with.html

    and original firm marlin for K40 https://github.com/TurnkeyTyranny/buildlog-lasercutter-marlin

    fin this with first duets, only with diode : https://reprap.org/forum/read.php?133,521301

    is possible control pwm 5V with duet? use fan port with 5V?

    I'm a little lost to start the conversion, or if possible, although it seems that there will be no problem.


  • You might want to glance over this ongoing(ish) thread:

    In particular @Danal 's circuiit here

    edit: And maybe the same link I just posted since the laser supply you show above is similar to what they discuss.

    • You will need to work out how to handle the fire line as well as the PWM one; I think it is used as an enable pin, but I'm not sure how people normally handle it.

  • I think it is not the same since it is a diode.

    I found info about the source, it is the green version of this link


    alt text

    Green Supply

    Connector #1
    Pin #1 HIGH VOLTAGE Return (from ma meter)
    Pin #2 AC Ground – goes to Chassis Ground and Mains Ground
    Pin #3 AC IN #1
    Pin #4 AC IN #2 (In US, either can be Neutral)

    Connector #2
    Pin #1 (G) “Laser Switch”, “Test Switch”
    Pin #2 (P) “Laser Switch”
    Pin #3 (L) “Test Switch”
    Pin #4 (G) – Pot CCW Pin (turning knob ccw contacts this)
    Pin #5 (IN) – Pot Center Pin (0-5V DC output level control)
    Pin #6 (5V) – Pot CW Pin (turning knob cw contacts this)

    Connector #3
    Pin #1 24Vdc out – runs to motor controllers
    Pin #2 Ground
    Pin #3 5Vdc – Control power
    Pin #4 “L” or “LO” Laser control. This turns ON the 15KV power when pulled to ZERO volts (Negative logic)

    would this adapter work?


    ![alt text](ff03304b-9464-4738-9061-bbea531d0dd2-image.png image url)

  • i found in house this conversor, buy for control vfd from duet.

    is valid for control laser power supply?

    alt text

  • @hector said in Duet wiring K40 laser co2:

    I think it is not the same since it is a diode.

    5v TTL is the the same everywhere, and the laser power unit you list takes 5V control inputs. So the 5v version of the circuit @Danal shows will work to drive it from a Duet heater (or fan) output.

    However; your laser is controlled differently from most Diode lasers in the top diagram. The Laser PWM line sets the power (eg S xxx values) ; and the Laser Fire line is responding to on/off (M3/M5). Most diodes just use a single pin for both. (*)

    You can use the PWM to analogue converters above for the Laser PWM line. But you will still need something like the circuits in the other thread to control the 'fire' signal.

    (*) The K40 is an old design, the original controllers it used were very simple; the user did power setting for the cut on a potentiometer via the 'laser PWM' line, and the laser was run at that power during the whole operation, switched by the 'Laser Fire' line between cuts.

    • These are laser Cutters, dont confuse them with low power diode laser engravers, which need more flexibility in the power output..

    This controller has three inputs, two TTL type digital inputs; one as a door/coolant interlock, the other is the 'fire' signal; plus the 0-5v analogue level control labelled as 'PWM' in the top diagram.
    My advice would be:

    • Leave the door/coolant circuit untouched, it is important to protect both you and the laser.
    • Wire the 'PWM' line to 5V, (or to a potentiometer as described in the text if you want a manual power override)
    • Use a zener circuit to drive the 'Fire' line with PWM directly from a Heater output on the Duet. Varying the TTL PWM on that will vary the laser power.

  • A little point for people to note:

    The CNC community seem to have some sort of mental block about what 'PWM' means. It is commonly used to refer to analog signals, or to frequency, or both. Or even as 'a sort of Pot' (yep, really). So be careful when old school CNC experts write about controllers, they will use 'PWM' to mean 'variable voltage'.
    They will also talk about PWM frequency as being the same as the (low) pulse frequencies used in some laser systems and cut types. Or get frequency and duty cycle thoroughly mixed up.
    It all gets quite confusing; don't get suckered by the language.

  • @EasyTarget Could you specify more what you mean with a zener circuit? a single diode? I have seen an old model duet connected only with a diode.

    The protection circuit of the door, water and emergency button are in series, so we only need to control the fire pin if we connect the IN pin directly to 5V?

    Thank you!

  • @hector said in Duet wiring K40 laser co2:

    Could you specify more what you mean with a zener circuit?

    I was referring to the circuit shown in the thread that I linked to in my first reply, using a zener diode and a resistor bridge to give a 5v TTL output from a heater circuit.

    The protection circuit of the door, water and emergency button are in series, so we only need to control the fire pin if we connect the IN pin directly to 5V?

    Yes; that sounds correct.

  • I will have to calculate it again since we use 24V, right?

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