Connecting 12 V Laser Module to 24 V Control Board

Question

I have a 3D printer (Artillery Genius Pro) with a 24 V motherboard. I want to connect this motherboard a 12 V laser engraver module. If my motherboard was 12 V (with 12 V, GND, and PWM pins), I believe I could do it. In that case, I would connect 12 V, GND, and PWM of the laser module to 12 V, GND and Blower Fan (as PWM) of the motherboard. But my 3D printer has a 24 V board. How can I connect my 12 V laser module to my 24 V motherboard?

Your guidance in this direction will be highly appreciated.

Answer 1

Get a proper module

The most straightforward solution would be to get a 24 V rated laser module. However, that boat already departed (unless you can send it back and get a proper one in return).

The fan could be a 5 V signal, a 12 V, or a 24 V one, so make sure your laser module uses that as a trigger.

Often, laser modules line their output directly to their power supply and have no extra switch wires - using the main heater cartridge connectors as the power supply and switch will certainly work on its own, once you get the proper voltage set.

Buck Converter

To get from 24 V to 12 V, you can use a Buck converter, in this application also known as a Step-Down-Converter. This will turn the 24 V output of the mainboard's heater wires into useable 12 V power. Often, these items have quick-connect plugs, possibly allowing you to quickly swap the laser module in, provided you have everything else set up similarly.

Please keep in mind that these modules, depending on setup, can shed quite some heat, and might require a suitable cooling setup. Heating can also indicate bad manufacture.

Voltage divider

If you can be really sure that you get 24 V Output max, you could use a beefy 1:1 voltage divider by using two same-sized resistors and taking the supply voltage between the two before going back to the ground. To alleviate heating problems (you'll shed loads of heat) you should use resistors that have cooling planned in.

Optocoupler

If you want to run the laser from an external 12V, you could run that though an appropriate optocoupler and use any output from the printer as your "signal" to allow power to flow.

Answer 2

I have converted a 3D printer to a laser printer using the fan port. Although it is possible, I would not suggest to use the fan port for this.

First, make sure what your laser module uses as input. E.g. my laser module could be run from a 12 V power connection, so I did not power it from the printer controller board. Second, make sure the TTL (the PWM signal for scheduling the laser intensity) is able to handle the voltage you send to it. If you use a 24 V controller board, it could be that the fan (as well as the heater cartridge and the bed) run at 24 V. If so, you need to step down the voltage so that the laser module can use this.

Note that when using the fan port as the PWM signal for the laser, you introduce a lag. The controller board chip sends out a signal to the MOSFET to schedule the fan as this is drawing more amperes than could have been supplied over the controller chip. This creates a lag in between the actual controller board pin and the fan signal causing the actual laser engraving to be less accurate (started too late, stopped too late). It was that much that I had to create an application in Python that read created G-code and introduced very small pauses to give the laser time to start and have it stop on time because of the delay. This has led me to directly use the PWM signal (that drives the MOSFET) instead of the fan PWM signal for controlling the laser.

Answer 3

You'll need a 12 V step-down regulator to convert your 24 V to 12V, or a separate power supply for the laser module (make sure to connect each PSU's ground terminals).

It also depends on what sort of PWM your module expects. The fan control on 3D printer boards is done by turning on and off the ground connection to the fan, while the positive supply (12/24 V) is on constantly. This may not be what your module requires.

Maybe it's fine with a 5 V PWM signal (usually called "TTL signal"), in which case you could use any available digital pin (e.g. from the endstop connectors) and set your firmware up to use that pin as the "fan". Depending on the firmware, there may be delays between the change in "fan speed" / laser power being scheduled and it actually being applied. If it needs 12 V PWM, I like using L298N-based "motor drivers" to drive loads like this. Hook up the inputs to the motor driver to the output of the step-down regulator and connect the corresponding input to one of your motherboard's PWM pins.