So according to Lasertree, if PWM is present when it powers up it will fire immediately then work normally.
My setup is a C3D Mini using pin 2.4 and the Mini is powered off the power adapter board of the Lasertree, at 24v of course. So the issue is power goes to everything at once. If I plug in the PWM cable after power on, its fine.
So either I need a magic setting OR a device to delay the laser power up or the PWM line. I can think of a few kludgy solutions but hopefully someone has already found a good solution.
Sorry, this happens before the C3D Mini has booted, so any delay would not be invoked yet.
This has to be an issue with any Lasertree LT-4LDS-V2 running off a C3D board and Iād guess most other basic controllers. Not an expert but my theory is the PWM line is apparently high as soon as power comes on then its under the firm/software control. This is obviously a HUGE safety issue so I think IF its common to many controllers, there must be a solution, hopefully simple. But even if I have to design(well find) a latch circuit I need to prevent full power out bursts!
Iām guessing there isnāt also a separate enable line?
PWM in is the āenableā so it just 3 wires into the LT-4LDS-V2
You are on the right track, and itās something others have hit before. The PWM line on the controller starts in a floating state, and is only pulled low as the firmware initialises.
Most Microcontrollers leave their IO pins in a āfloatā (High-impedence, high-z) state on boot, and if the laser module itself has an internal pullup on the PWM line (again, most do) you get the laser on until the board sets the pin low during initialisation.
A pulldown resistor on the PWM line should work; the pullup in the laser module is probably a very high value, so a 2.2K pulldown will probably be enough. You will typically see some sort of protection / pulldown guarding the PWM on better designed boards; but my ābare metalā esp32 board suffered from this by default.
I āsolvedā it using FluidNCās separate āenableā output; driving a mosfet board that only turns on the fans and laser module when commanded; and is properly biased so it does not trigger during reboots
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I think this is unlikely. If you applied power only it would lase.
Most devices pull an input to the off state. It has to be driven high by the external device.
Itās more likely that the controller is pulling it high for a short duration before it goes lowā¦
Anyone have a scope?
I have four diode laser modules and they are all default biased to āonā and come on full as soon as the power is applied, only one has jumper you can remove to cancel this. This topic has been discussed before; especially wrt FluidNC (nee. GRBL-ESP32); this is why well designed boards have a pulldown on the laser pwm pin.
Itās dangerous but sure cuts down on those pesky āI unboxed and plugged my laser in and it doesnt work!!ā support calls.
Thatās sad to hear that.
I have four of them also and they will not lase when just power is applied. Except the one that is a two wire module (500mW).
That is just flat dangerousā¦
Iād like to see what a scope saysā¦
This seems to be the easiest off the shelf solution unless your into hobby electronic and want to play with 555s. Anyway, all solid-state rated enough should handle a 40w optical power Diode at 24v. Also you can get a version with a good ole relay for $8 which is what Iām going to use first. Question is do I use it for the PWM signal or power? As either would do the job, decisions, decisions 
https://www.amazon.com/Timer-Delay-Relay-Cycling-Trigger/dp/B0B664VDWP/ref=sr_1_6?keywords=Timers.Shop&qid=1701744368&sr=8-6
Late to the party here:
- Need link to laser tree module.
- Have you tried powering on the machine with the PWM disconnected from the C3D to see if itās the controller is firing it?
- I have seen this problem on CO2 lasers if the PWM is the wrong resting state (inverted).
Are you sure this laser module runs on 24V?
Do you plan on delaying the power to the laser module after the machine first powers on? If so it should only be in the source power circuit.
Something is not right here IMO. If this situation is normal behaviour for a laser module it would create a safety problem even when powered on a bench.
My machine [which does not use this module] does not behave like this.
Yes as you can see it is 24v. The problem is as Owen described above, the C3D Mini has a floating PWM line during powerup or it is purposely cycled high before low the first time. Either way the real issue does not seem to be the LT unit, its the C3D Mini.
So yes, upon power up a time delay relay powers it after the C3D Mini has booted fully.
Yes I see now that it runs on 24V, good to know.
I still suspect there is something wrong with the drive, not the laser.
Didnāt see an answer to this question.
Did you try inverting the PWM signal in the C3D configuration?
Don, thanks for getting involved, always too to have OG help.
Yes, without PWM hooked up powerup does not fire the laser. Just to be clear, WITH PWM connected the laser fires immediately on powerup, seems to increase intensity for a moment then goes off. Guess the power level is 20-40% judging from the burn.
No I have not inverted the signal as it works properly both via GLCD and Lightburn without being inverted. I canāt think of any mechanism that would let it work properly with either std. or inverted so why try?
While the answer to this question will be informative this makes me ask why does the K40 not fire with the C3D if the signal is the issue? Is the C3D booting faster than the powersupply etc can fire the laser? Or does the PS have a pull down on input, seems to me a pull down would work on either end of the PWM signal.
Also I will eventually try to add a pull down as I have a good stock of old school non SMD resistors. Right now my āsolutionā is to use a supposed time delay relay(on the power) which actually is functioning as a NO latch, when power is applied the relay is open then push a momentary button and its powered sending 24v to the laser. This does have the advantage the laser does not run until you want, which saves wear and tear during verification(I often let it run without lasing to make sure what its doing), so a sort of a lazy persons auto switch. Iām usually pretty good posting results etc. so Iāll get back to this later this week once my honeycomb ventilation is done.
Considering all the controllers I have helped get connected (100ās) not a single one needed a start-up relay. Multiple of these projects did have challenges with fire@start.
This is why I think the problem has to do with the PWM polarity and its resting state. K40ās do not have this problem because the K40 LPS is expecting a ground to fire.
I have worked with controllers that had the wrong PWM polarity set and the symptoms were the same. Your case may be different.
I imagine you canāt see much of what is happening with a DVM, do you have a scopeā¦?
FWIW, I read others having the same issue with the Lasertree, maybe it is user error.
Regardless, so you are speaking of inverting the pulse polarity versus inverting which end of the PWM range is full power? Just for giggles since you are spending the time to help, I checkedā¦the signal is inverted (!) and when NOT inverted, the laser fires and keeps firing on startup. So that is not an option as far as I can see.
So when you invert the signal it stays on all the time?
We need to somehow measure exactly what is going onā¦
In any case, I have to believe there is a better way than adding a clunky relay 
I will go look at the C3D min output.
yes its stays on full power until I turn it off. If you have any resources beyond the knowledge base etc. that is online Iād love to have it.
yes, a solid state relay 
Going back, yes, sort of I can see whats going on as I do have a logic analyser. Problem is I am a noob with it and its a bigger rabbit hole than the laser. I presume Iād need to know the PWM freq. 20Khz?
Ideally, we just need to see the transition during power-up. Not sure a logic analyzer will show that but its may be worth a try.
I see you are connected to P2.6 which is JP1.
Exactly what pins are you using and how is it connected to the laser module.