+Peter van der Walt an analog output to IN (0-5v) and set the max power from a control panel widget in laserweb? Get rid of the pot.
Actually, just add the max power control to Laserweb and use an open drain PWM to IN, get rid of the pot.
So the way mine is wired theres a 5v signal to IN and PWM goes to H (or L if I wanted to use a low level signal)
So the nano is only connected to the psu via 24v, 5v, L, G. Where do we connect the 5v to?
Most of the laser psus have a 5v output on them. You would tie that to the IN.
So in the K40 those. 5v would be connected to the IN in the pot. The would make max power on it and we control power via pwm? Is that it?
Or if you are going to tie IN to 5v anyway you can leave the pot connected to it and turn it up to full power or a nominal Max safe power (e.g. 18ma). Then you have some freedom to do real time adjustments.
I do not have a TH/TL pin on my supply.
Lol I’m so lost… there are so many ways these can be wired I wish I had Line diagram so I don’t mess it up
+Peter van der Walt LMAO!!
#rotarytoolsupportpleaseneedtoengrve50whiskeyglasses
#nohashtagnovalid
+Peter van der Walt the L pin in the power connector? Has anyone tried this, some testing shows it will not respond to a pwm signal and it’s low true so no invert?
@donkjr I was able to pwm the L pin. My psu appears to power on much faster than it powers down between pulses, so i had to greatly increase the pwm period (decrease the frequency) to find a rate where the output responded linearly. It works fine now but it would be nice if the software supported a correction curve to map power to duty cycle for more flexibility in setting this up. It would also allow one to even get rid of the offset when using pwm on the IN line.
@Vince_Lee when you say you decreased the frequency do you mean that you changed the PWM period in the configuration file to something longer than 20MS?
Does this infer that the LPS takes longer than 20MS to shut off?
I wondered how the 20MS was chosen.
I wonder does this create a problem with engraving quality?
@donkjr Yes, I don’t have the final number in front of me, but I’m using a period much higher than 20uS. In order for PWM to work on a digital input, it seems to me that the frequency has to be faster than the power supply can respond, otherwise you’d just be pulsing dots instead of reducing power. But at the same time, you don’t want the frequency to be so fast that the power supply treats intermediate values as constant-on or constant-off. With the default period, I found that the laser jumps up to near full power anytime the pwm power level as moved much more than zero, which implies to me my power supply can turn on more quickly than it can turn off. As for engraving quality, it’s possible pwm can affect things, but even at a 200 microsecond period (10x) if engraving at a fast 500mm/s, that spaces pulses 1/20mm apart on the engraved piece.
@Vince_Lee lately I have been wondering about the whole response picture including the PWM input, PS response and the tubes response.
BTW do you mean milliseconds in the above?
It makes sense that the period must be long enough for the laser to react (go high and then low) before the next cycle.
I watched https://youtu.be/BXJTSBeywHQ with interest. The “pre-ignition” discussion started me wondering if at low powers the response is different than at high powers?
I am back from vacation and plan to set up a test that looks at the entire system from PWM to laser light.
My plan is to build an adjustable PWM generator and an IR sensor at the bed. Then I can look at both on my scope with the intention of understanding better how the entire system responds to various PWM inputs.
First I have to figure out how to measure the output power at the bed from 0-40 watts without frying anything :).
@donkjr hi very nice write up you have by the way. The comment in my config file says that the value entered there is in microseconds, but I have no other info confirming this. I checked my wiring again and I think I might have a slightly different psu than most. The one I have matches the one in the following post (not mine, but a ref I used for my conversion). I have kept all the existing wiring and simply replaced (inserted inline actually) my switchable adapter board at the controller board connectors, so the line I am controlling with pwm is the “L” line in the diagram. I left the pot, test fire, and safety enable switch in place. http://3dprintzothar.blogspot.com/2014/08/40-watt-chinese-co2-laser-upgrade-with.html
@Vince_Lee I think the mystery is solved, you are using “L” or sometimes called “TL” on the control section of the supply. The one that we were talking about that does not work is the L on the power connector. 