A small program running in a microcontroller to place between a laser engraver controller and the laser module to always turn the laser on at a very low duty cycle, permitting to see the dot to adjust the focus, position and alignment.
Just build it using "make MCU=" with the microcontroller name (attiny85 and attiny13 are currently supported, others may be trivially added).
It has no dependency beyond an AVR toolchain like the one provided with any Arduino IDE. The program can also trivially be imported as an Arduino project for those more familiar with this heavier approach.
A circuit is provided, made of a schematic and a board, for those who want to quickly implement it. It's made around an ATTINY13A which is as cheap as a 555 these days. The output uses 4 pins at 2.0 pitch to match my NEJE-20W laser module, and the input uses a male JST-XH 2.54mm connector to match the connector at the end of the cable on the laser module side. It's worth noting that the cable is not straight but reversed, so the polarity here really requires the cable or needs to be reversed.
The micro-controller may be programmed in situ using an SOP8 clamp provided the module is disconnected from both sides. Indeed, no pin prevents this from being done since there are no local component connections. I'm also using this to program a different duty cycle in its EEPROM, like here, 0.2% duty cycle :
$ avrdude -c buspirate -P /dev/ttyUSB0 -p attiny13 -U eeprom:w:0x02:m
