How to connect a new momentary switch to GWWG power supply

Hello New to the forum and new to K40. I got my K40 and have been testing it out. I am now in the process of replacing the digital Controller with analog. i know how to wire up the potentiometer and the Amp Meter. I am looking for info on how to connect a new momentary switch to the Power supply. I have the GWWG style of PS. What two wires should i connect to the momentary switch? K+ and the ground?

Any help would be appreciated.



Since you got K+, there should be K- right next to it. K- is just another ground. K+ and K- are intended for the momentary fire switch.

With some PSUs, the K+ and K- labels are the wrong way around, but that doesn’t matter if you just connect a momentary switch to it.

Curious, what do you want to do with the momentary switch?
What about the fire switch that stock on the panel?

If he gets rid of the digital control panel (LEDPAD-A, PowerLED), its test switch will be also gone.

Other things which will be gone are the activity LED and, depending on the version, there also might be an “enable/disable” button which toggles the voltage going to IN on and off.

My panel sort of had that on/off button. The PCB had it, but the foil they put on top didn’t. Naturally, they just ripped the cap of that button to remove this feature completely. Lol. Well, I guess that’s better than having an invisible button which disables the laser.

Personally, I don’t think that on/off switch is very useful. It’s kinda like an interlock switch which you have to flip yourself. I honestly don’t see the point. If you want an interlock-like safety feature, install an interlock switch.

Ah I did not get that the entire panel would be replaced!
The enable button is a way for the operator to ack that the machine is made unsafe.
In spite of interlocks its good for the operator to have to take an action to make the machine unsafe.
I would not like a machine that was unsafe when the covers were closed without my actually having to do something to make it unsafe.

Well, the machine has to be turned on, the lid has to be closed, and then you have to press a button or start a job. Depending on the controller and how it’s configured, actually starting the job may require pressing a button on the control panel.

That’s enough hoops for me. The expensive machines by Trotec and Epilog also don’t have another switch for arming the machine.

A safety feature which you have to manually enable/disable dozens of times a day is very error-prone.

Safety features should be automatic or an integral unskippable part of the workflow. E.g. if you have some kind of press which stamps parts out of sheet metal, you can ensure that the worker won’t squish their fingers by making them press two buttons on the left and right side of the machine simultaneously. They can’t squish their fingers because both of their hands are occupied with pressing these buttons. No matter how much they zone out, they won’t screw this up.

With a laser cutter, the machine could disarm itself when a job is complete or when you open the lid.

That would work. But does this extra step really add anything?

What is error prone about a switch? You mean you turned it on when you did not intend to or you did not turn it on when you were supposed to?

Forgetting to turn it on before a job starts is annoying but its a small price to pay for some* protection against and accident like an interlock bypassed and forgotten.

Laser systems are very different than mechanical ones. Unless warned the user does not see that the laser is on and the environment can be unsafe. This is especially true of CO2 lasers.

Frankly, if I had my way… I would have a deadman switch… on a laser systems where a human could be exposed.

Done correctly the user should be warned any time the laser is on vs it sitting quietly armed. If the machine showed [blinking light or annunciator] it was on I would feel better about it sitting silently armed with the covers closed.

Laser safety systems should be designed such that they keep anyone within range informed any time that the laser is on. They also should be designed to keep the operator safe in case any element of the safety systems were to fail.

Automated systems to turn the laser on and off could be used if they did not employ electronics as they can fail to easily and are not considered safe enough.

A good resource is to examine is the federal laser class standards for system design required for a product to pass its federal laser safety classification.

But, most of these cheap machines do not meet even the minimal requirements and most makers do not spend the time to design-in minimal safety features much less consider all the safety failure modes. This is true for the laser and the HV subsystems.

*So it may be fruitless to argue if an arm button is enough better than no arm button since the user is generally not protected against laser safety system failures anyway.

Comprehensive laser safety is not convenient nor workflow efficient it does however save you sight.

After having pressed it dozens of times, you’ll get in a rhythm and press it without thinking about it.

You can get interrupted at any point in your workflow.

E.g. you load the machine, close the lid, press the arm button (as you always do right after you close the lid), you get briefly distracted and then you notice that one of the items isn’t properly seated in your jig. So, you open the lid and… well, you forgot to disarm the machine. Oops.

You don’t have this problem with something automatic like an interlock switch. If you open the lid, the laser is disabled (and the controller may pause automatically).

Well, all the lights are on and the fans are running. The machine is unmistakably turned on.

You can also have those multi-color status lights which show if the machine is idle or if some job is running like this one from a random Alibaba listing:

The better machines have redundant interlock switches.

With some machines, overriding the interlock switches requires a special tool/key which, when inserted, prevents the lid from closing. This too is one of those things which prevents human error. You can’t leave the tool/key there by accident.