So I started some tests to see what kind of mA the tube draws. LCD menu only has 20% and 50% settings to test fire. But its pretty easy to modify ultralcd.cpp to define different power settings.
The surprising part is at 40% power it only draws 3.5mA and its jumps to 10mA at 45%. At 50% its 13mA. So I need to find sweet spot between 40 and 45 now.
As @Scott_Thorne suggested I will try to not go over 7mA. May be then I can modify the code to never exceed that by changing the range of PWM.
Ok so just got done testing 40 to 44% power and results are super strange.
When the current drops I can see the laser beams inside the tube also kind of powers down. I mean you can literally see the brightness goes down.
So what is that ? Is that Lower quality tube for something to do with power supply? I see on LightObject website they states that “Unlike other low quality tubes you may find on eBay, this tube is made by a reputable company. The output is very stable with a low divergence.”
Any idea folks ?
If at 44% you get a stable 10ma output…then it’s neither the tube or the power supply, sounds like the controller to me…I guess it could be the supply but unlikely.
do you check with a oscilloscope ?
maybe I am wrong, but my understanding is the signal is square in V (cheap PSU). that mean X% is the percentage of TIME the signal is at v Volt (define by pot).
PWM is nothing to do with Amp (except maybe the time needed for chemical reaction to happen in the tube and before saturation).
This why I kept the pot in my mod (to control max mA). but I don’t have a oscillo, and the VU meter is useless at those frequency.
edit: Sorry I was a bit slow this morning, your % is showing a digital pot log curve (with 5v max =100%) and corresponding power.
it seem this digital version isn’t better calibrated than the analog one ;-((
@StephaneBUISSON Thanks for your help. The thing is If I am running some gcode at the same power level but with PPM=40, the mA on the Analogue meter stays stable. But it drops like the video I posted only when I keep the Laser Fire switch pressed. So that made me think that Instead of continuous laser if I keep it pulsing the power stays stable.
