Hi All,
I have a K40 and just updated the PCB to a Monport so it will work with Lightburn.
After reading and watching several articles I think I’m setting the power output for a layer correctly but it’s still too powerful.
I have set the layer output power to 0.1% dropping it from 1% yet it still cuts through 2mm Baswood and the Amp meter shows 5ma.
When I had the old PCB and was using Meerk40t I could set the power very low using the front panel and 5% hardly turned the laser on.
Cheers
Many of the new monport board handle the interface between it and the laser power supply (lps) unlike some of the other boards.
In simple terms most K40’s set the current level with the console pot and then turn the tube on/off as a digital device at the pot set current level using the pwm output of the control card.
Monport has changed some of their boards to use the pwm to drive the IN terminal directly (where the pot used to connect), eliminating the manual pot control.
Do you know how yours is wired?
If you have a voltmeter, I’d check the IN terminal of the lps to see what voltage is there, this controls current limiting.
Make sense?
Hi Jack,
Thanks for the reply, I have attached a couple of pictures that might help.
The old wires where connect to K- G IN 5v the new Monport board only has a Red and and Black wires that go into the G IN 5v connector, assuming G (Black) IN (Red)
Having the old connectors plugged in I managed to test the voltage and it appears to go from 0 - 5v when I change the power output on the front panel.
One thing I did try was to measure the output at the connector that would go into the PSU from the monport but this was hard and whilst trying to do this test the laser output a strong beam which I found a little confusing as the PSU had no control plugged in, neither monport or original controls!
Update: OK more testing done, with original controls the voltage at IN goes from 360mv to 5v when measuring Monport output at same pins minimum is 680ma! this look at be the problem, the fact the Monport cannot output low (PWM) voltages! If I am correct this isn’t very good from a supplier that says their control outperform the standard control!
I don’t think these should lase with the control wires removed. This would be a basic dangerous idea … if you power it up it lases… not a good idea.
I think what Monport has done is to use the pwm to control the current via the IN terminal. That’s why there is no manual current control. This is actually the correct way to control a glass tube laser.
Is this the board you have?
I need to hunt around after the lps you’re using, it’s specifically for the K40 types and the labels are different, although it’s pretty much the same thing. It supplies 5V to the control board.
At a 10% power setting there should be 20% of 5V on the IN pin (1V) or you can chase it back to the control board and measure it there. This controls tube current. If this is higher than the 1V your monport board isn’t outputing what it should.
Have you checked the $30 = 1000, $31 = 0 and $32 = 1? Also the S Value Max number needs to be equal to the $30 value.
Yes that’s the board I have.
OK more testing done, with original controls the voltage at IN goes from 360mv to 5v when measuring Monport output at same pins minimum is 680ma! this look at be the problem, the fact the Monport cannot output low (PWM) voltages! If I am correct this isn’t very good from a supplier that says their control outperform the standard control!
All parameters checked and correct
20% = 1.4v 50% = 2.8v from monport.
This would indicate your lps is having an issue with current control. Makes sense if it lases without any connections.
I don’t know any of this stuff that has a 680mA current or for that matter even 68mA so I don’t follow you here.
Doh! mV not mA
Regarding lasing without connections, I’ll test this again and take a picture.
I had all the wires off and was trying to check the voltage at the end of the PWM (Red/Black) wires out of the Monport, when I ran the test file to get monport to output a PWM the laser fired, but as I say I will check this.
Is it the LPS thats having issues? We have proved it can work with the original controls down as low as 360mV and when I up the % on the original controls the mV goes up. then we have established that the Monport outputs different PWM voltages at different % settings so this works, it just appears that at 1% in Lightburn (the lowest allowed setting) that the output voltage is 680mV and the original controller can output as low as 360mV. I don’t have any scope leads to hand at the moment but I will grab some and look at the PWM from both and post the results.
If I’m following you, I’d think lps. The way Monport connects these any voltage on the pwm may result in it lasing.
If you are disconnected from the lps, and it still lases when you run it, I think there is an issue. Usually these don’t lase unless they are connected.
Sounds like there is a large change in voltage to the IN terminal from the Monport pwm and your laser should reflect those variations. Most of these won’t lase below about 10% anyway, so I doubt you’d see a 3% lase. 0.6V on the pwm would indicate about 3% power.
Have you checked the variable I asked about and ensured they are correct? Did you hear from the manufacturer?
OK Got round to measuring the PWM on both original PCB and Monport. Both set to 6% as this is the lowest the original controls will go and output a beam (great for cutting A4 paper).
Clearly Monport is outputting a higher voltage (faster PWM) and even if you drop this to 1% it make no difference.
Left hand pics are 5us per division and right hand set are 200us.
Not sure what I’m looking at. I did notice that the peak to peak voltages are over 5V, which is curious. Most of these use a controller of either 3.3V or 5V cpu types. 3.3V cpu usually have a voltage translator so the output to the lps is within specifications of a ttl signal (0 to 5V). Without a higher supply voltage, I don’t know where these >5V are originating.
PWM is not frequency or voltage dependent, a faster pwm isn’t going to produce a higher voltage. If the tools you’re using are indicating a higher than 5V I’d question where these values are coming from.
If I measure the pwm output of my Ruida, which has a period of 50 u/S (20kHz) or from my little cnc which has a period of 1mS (1kHz), 50% power reads 2.5V on either machine.
It’s also difficult without some type of schematic to have some clue as to what/how they are doing.
Hmmm not sure you know how PWM work or TTL.
TTL max is NOT max 5v it is tied to VDD, this can be higher than 5v but VDD has to of course fall within the max tolerance of the components it’s supplying.
PWM is directly tied to how fast the ON pulses are! or more technically the duty cycle, the more often it is on in a given time on the higher the analog voltage you will read.
So when you see more ON pulses (higher duty cycle) within a time period and compare this with another PWM signal using the same time period and you see a lower duty cycle then you can categorically say one will produce a lower analog voltage reading!
This is why the Monport when set at 6% has a higher output than the original controls set at 6%. because the Monport PWM duty cycle is higher.
This is not true… however if you wish to believe that and since you seem convinced, I won’t argue.
I gave you the information in my previous post, it’s up to you if you want to believe it or not.
The proof, explanation of how TTL voltages are never 5v exactly and are often above.
Pwm diagram proving the more ON time the higher the voltage reading.
Thanks for the offer but it’s clear that the Monport is outputting a high more often at 6% than the standard controller leading to a higher voltage, I think I’ll give your offer of help a miss.
TTL is defined by a 0 to 5V signal. Nothing is perfect and this means that a 5V supply can vary, there is no argument. Little, if anything is exactly what’s it’s noted to be…
You seem to support what I was saying, except this has nothing to do with period, faster frequency.
Surprisingly your scope is measuring 5.5V peak which is above what most regulators will allow for a 5V signal and I’d expect your pwm output to reflect that. There is a lot of noise on the ground side of your pwm scope trace.
If this didn’t work as I stated, none of this junk would work.
If we can’t agree on something this simple, I’ll have to refrain, as I’ll be of no help. There are others here that may help.
Good luck
TTL Max is VCC not 5v, 5v is an ideal as is ground being 0v. The pwm wave we see is an acceptable waveform for a TTL PWM in the thousands of PWM waves I’ve seen in many different circuits.
As for the basic problem of one controller giving a higher power output at a given % setting
The longer a PWM signal is high in a given time period the colser to the maximum voltage will be read.
Both PWM signals were read with a timebase of 5us, during a 20us period the old controller was high for 2us whilst the monport was high for 4us, are you are saying that has no effect on the voltage you would read? Even though when actually reading these voltages we bizarrely read almost double the voltage 360mv and 680mv!
So, we see double the duty cycle Ton/(Ton+Toff) or 4us/(10us) = 0.4% vs 2us/(10us) = 0.2% and coincidently we read almost an identical doubling of voltage and you are trying to say they arn"t related?
It is clear the monport outputs a higher PWM frequency but more importantly a higher duty cycle at 6% but this is actually not the real problem as the monport can’t actually go below a 0.4% duty cycle resulting in a minimum voltage of 680mv.
Isn’t the IN pin on the LPS analog? If so, a higher control voltage will result in higher output irrespective of duty cycle. 5.5V signal would result in 10% higher outputs across the range.
Can you run $$ in Console and confirm the values for $30, $31, $32, and $33 (if it exists).
Alternatively, have you looked at running LightBurn over Meerk40t using Ruida or GRBL emulation modes?
