More description of the problem and clearer explanation or you won't get any help here
SMF - Just Installed!
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Sometimes, I read the various forums I'm active on and feel smart. Sometimes I feel like the dumbest person there.
So, I'll have you smart engineer types that are making me feel dumb tonight know, I can drink beer through my nose and hum The Star Spangled Banner at the same time. Take that !
I am "assuming" that the manufacturer actually has tested the circuit with a ttl level drive such as the 5V AVR used on their associated controller. I have been using my home controller board with a 3.3V STM32F303 chip. Next rev (hopefully the last) is about ready and want to have a warm feeling that the TTL port is ok. Guess I should just order one prior to getting the controllers built.
FWIW, I figured out what value resistance to place across the TTL input on my laser controller empirically. I stuck a pot across the input and cranked down the resistance until the laser turned off, took about 3/4 of that value and have been running mine with a 1K6 resistor across the input for a while. Mine had a 5k1 pull-up on the board. Others here have showed concern regarding the extra loading on the Nano but it works for me. YMMV.
This is becoming a very popular question on this forum. There are several options available for a fix depending on the owners expertise. Not everyone understands electronics, wants to modify the foil traces or unsolder components on their brand new laser module. It would be nice to establish a "work flow" so when it comes up again, the forum member has an organized method to follow. I realize there are a lot of different controllers out there to deal with so a general work flow would seem appropriate.
One thing I fear though is what happens when the engraving is done? Hopefully the laser stays off!