You should have a 3.3V supply on the monport board… This things draw very little current.
Seems odd it would make it out of the shop like this.
Made this new cable to bring 5v from the power supply to the level converter. I don’t see any useable 3.3v power on the board so tomorrow I’ll use the said buck to convert the 24v pin to 3.3v. (Monport tech support has emailed me saying they will be shipping me out a new level converter, which is what they assume the issue is)
Hopefully with the necessary cabling included?
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Highly doubt.
Ok…so I got the buck and self purchased level converter. Pulling up 5vDC from the power supply to the High side of the converter and 24vDC–>3.3vDC from the Monport v2 board through the buck and into the Low side of the converter. Still having the same issue.
I command Lightburn to fire at 100% giving me 3.27vDC on the Board Low Side and 2.84vDC on the board High side. (6mA laser power - Dial set for 14mA max)
At 50% laser power I’m getting 1.69vDC on the Low side and 1.49vDC on High Side
Wish I had a scope.
(Ignore the colors in my drawing)
That’s odd.
Did you probe the 5V from the LPS to confirm power?
I see a few possibilities based on this:
- The level converter isn’t working correctly. Possibly try one of the other channels.
- The understanding of your controller working at 3.3V with normal PWM behavior is incorrect. This doesn’t seem likely but it’s possible. Not sure how this could be validated without a scope.
- Something is wired incorrectly. Double check the wiring and make sure nothing is amiss.
Are you sure the grounds on the buck converter are the same? I’ve seen these where the grounds were isolated…
Do you have a schematic or link of the level converter?
Ok I just went through these one by one. Used 2 different level converters from the 4 pack.
LPS is supplying a steady 5v to the Level Converter, even while lasing.
- PWM —> LV1
- LV1 —> HV1
- HV1 —> LPS IN
- Board Ground —> Buck Ground —> Level Converter Ground —> LPS Ground
- Board 24V —> IN + Buck —> OUT + Buck 3.3v —> Level Converter LV
- LPS 5v —> Level Converter HV
Ground is not isolated thankfully, that would have thrown me for a loop. I hyperlinked the products purchased in my previous post. 
.
Going to try this.
This was a no go. Regardless of channel still same results. It is exactly as if it is just not doing anything.
If you supply a steady 3.3V to one of the low voltage side channels, do you get 5V on the other side?
Just checked, I do indeed get 5v on the high side if i supply a steady 3.3v on the low side.
Trying to think through the possibilities:
- The level converter is failing at PWM frequency. Do you have another known working PWM device at 3.3 volts that you could test this with?
$33-$39 have odd values so not sure what these are being used for. Do you have documentation on Monport extended GRBL configuration? $33=1 to mean 1Hz doesn’t seem likely. - Board is not actually a 3.3V device. Board is 5V device but only getting to 66% duty cycle at 100% power. What is voltage at board at 50% power?
- Feel like there’s another scenario I’m not considering but can’t put my finger on it.
I was hoping it wasn’t, for the record.
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My thoughts exactly, however I don’t have an alternate source nor any documentation from Monport. Going to see if I can borrow a scope. Also, I cant change the $33 value but I’m hoping that it means it’s 1kHz
About 1.645vDC
There’s a clear voltage drain somewhere on the 5v side of the converter, going to try a different converter. Possibly this one.
That would be nice to help remove speculation.
This best matches a 3.3V logic level…
Have you tried working with the original converter board as well by powering both sides of the convertor?
Yep, same result. A constant 3.3v voltage gives me 5v on the other side but a PWM 3.3v give me 2.84v on the 5v side. At least it has a green LED that lights up to let me know it’s actually on. and I’m pretty sure I crossed wires on it halfway through testing so it is now toast, Monport is sending a replacement,
This is easily checked along with elimination of the control board and voltage translater.
Put a voltmeter on it and measure it at various pwm values. It should reflect that percentage on each… a 50% should produce output of 1/2 of 3.3V → voltage translator and the output should produce 1/2 of the 5V or 2.5V → lps. Check the output with and without a load
I doubt it’s a 5V board…
- MPU is a GD32F303xx Arm® Cortex®-M4 32-bit MCU.
- If this comes form the factory this way, it would not make sense
Really doubt it’s Lightburn… although the symptoms are there for a configuration issue.
This hardware, although very low cost, is really quite dependable…
Previous tests indicated 3.3V logic. However, without a scope, it’s not a direct measurement confirmation. I was leaving all potential possibilities on the table even if all signs indicated 3.3V.
The native logic level is not going to be 5V. However, many boards meant for use in lasers go to the effort of providing 5V PWM for the laser control signal. So the MCU voltage by itself can’t be used to determine logic voltage for PWM.
I agree, the DCS32 has a level converter and it’s lower cost 
It was stated…
This would make no sense. Why would a level converter be hacked in there and why would they ship him a new voltage translator is this wasn’t the case?
Highly dubious… However, my read is he did these tests only on a high state of 3.3V only, I’m suggestion he checks the pwm at different pwm values for a failure from too short a period.
Again, that’s unlikely since these a components have a quick response time. In any case, he can do this with the tools he has on hand and avoid finding a oscilloscope.
It’s more indicative of a configuration or wiring error…imho…
Is there an L terminal on these for laser enable? No L- which is commonly labled as a lps return.
I don’t disagree. However, I’m differentiating what’s deduced from what’s confirmed. The only thing we’ve heard is that OP saw others describe this as a “booster board” to correct the issue. Opening it revealed it to be level converter. I inferred this to mean they were using it to convert logic levels. But given how it was wired and behaving and nothing definitive from Monport on expected behavior I still put this in the unconfirmed category.
He tested at board with at least 100% and 50% power, all indicative of 3.3V logic. He tested after level converter across a wide range of values which are consistent with other symptoms. Again, strongly indicating that indeed the board is outputting 3.3V logic. However, still unconfirmed. What we don’t know is the PWM frequency. Default would be 1000Hz but nothing to confirm that.
If there’s a specific test to do then offer it. Not all logic convertors are built the same. But if these can support i2c frequencies then they should be good for 1KHz PWM.
Are you saying you believe the wiring is fundamentally incorrect from the factory?
OP appears to have this style of LPS but with the addition of the RJ-45 connector. L is at the far right connector and hasn’t been touched thus far.
