Serial USB Conection Problem

Hello guys, I have problems with disconnections.
I made a small, fine laser that I want to control via USB with an Arduino Uno clone and a CNC Shield V3.
I have the problem that my laser keeps refusing to do its job.
Regardless of whether I try it with LaserGRBL or with LightBurn, the machine always stops in the middle of the process.
I’ve tried several different cables, several UNO’s, changed the buffer settings and finally grounded all metal parts of the part.
In Lightburn, I’ve now noticed that when such a termination occurs, either an “o” or a “k” is displayed in the console.
Unfortunately, I didn’t get any further with searches, maybe someone here had a similar problem before.

LightBurn V 1.3.01
Arduino Uno GRBL 1.1
CNC Shield V3
USB Serial

Sounds like the usb connection to the grbl is failing. The ‘o’ or ‘k’ is probably an ok that didn’t make it back to the console, but I’m guessing.

USB is pretty dependable, but it dependability doesn’t seem to applicable to all devices.

Lightburn only calls systems routines to talk to the laser, so if it’s failing somewhere between the computer and the laser, it’s outside of Lightburn control…

Make sure you computer is not letting the usb connection go to sleep, that’s an issue I’ve heard of…

Does lightburn display disconnected in the laser window?


Hi, thanks for the quick response.
As I said, I’ve swapped the USB cable several times and I’ve also adjusted the setting for the USB connection’s sleep mode, nothing helps.

No, the laser is displayed as Bussy in the “Laser Window”. I can then cancel the process and start it again, then it runs for a while and the same thing happens again.

You’ve done all the right things… not sure what to suggest.

My best guess is it’s downstream of the computer and probably related to the controller…

Do you know if the firmware version on the controller is current … doesn’t have any issues?


Had the same issue but solved it, the cheapest solution was to put the power supply on its own circuit from all other on/off appliances in the house.
Had the same problem random disconnects, drove me crazy tried all sorts, in the end I found it was the Freezer, on same mains ring, every time it turned on or off it browned the board out, put it on a different mains ring and all is good, I did until I solved the problem use a inline home made UPS , but i just used an inverter off a car battery on a permanent digital charger. to run the machine, can buy a pre made one on amazon from about £50 upwards depending on the power demand, as it being supplied through a constantly charged battery via an inverter, its isolated form any spikes, in the house main power rings.
When the Freezer was causing the issue the compressor would kill the connection when it turned off and on as well as the extractor fan, now all seems to be ok with the freezer on a different loop.
There is a UPs here for £40

UPS Centre

Powercool Smart UPS 650VA (390 Watts) With 2 x UK Plug - UPS Centre

This Powercool UPS range is your ideal UPS power partner against power surges & spikes can lead to damaging your hardware call 0203 740 4318 for information

the wattage should be plenty for most hobby lasers
Induction motors like compressors, have a high demand on start up, and this causes a lot of boards to brown out. for a millisecond.

I’ve already tried it on my laptop and on my PC, the same crashes on both computers

It is not the Laptop or PC, the board will be Browning out will be the Arduino controller card, that will be most sensitive to spikes in power!.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.