Laser Power Supply Issue

Community Laser Talk
1

I’ve lurked here for a couple of years researching, obtaining and building a DIY (Futher Fabrications) machine with the following specs.

90W tube (23 mA max)
Ruida 6445S
Cloudray MYJG-100W Power Supply
Analog mA meter

This is my first CO2 machine, YAY!. After I got the machine mechanically/electrically assembled and the basics tested, I started the mirror alignment. I used 10% Ruida display max power at the controller during the alignment. Everything went fine with the alignment. I burned a couple of test shapes in Lightburn without any real issues other than getting used to the new software/hardware etc.

I then set out to set the max current on the LPS (23 mA actually desired, I’m using 24 mA, in the text here, because the math is easier, LOL). I searched around this forum and read several threads about this subject and settled on the jkwilborn method (50% Ruida display max power setting and turn the LPS pot CCW until the analog mA meter reads 12 mA).

Since it was my first CO2, I decided to be even “safer” and use 25% display max power and adjust the LPS pot until I got 6 mA on the meter). So this is what I did and didn’t have any apparent problems. I then set the display max power to 50%, did a pulse and got close to 24 mA. What!?!?! I set it back to 25%, pulse = 6 mA. Hmmm, not linear at all (I read that it wouldn’t be perfectly linear from 1-100% but sheesh).

I then set out on the “20 turn pot from hell” tweaker turning marathon trying to get it to be somewhat linear. Luckily I oriented the LPS so I could get to the pot easily. Also, my 20 turn pot was like a 40 turn pot, I got tired of counting turns.

I went back to searching these and other forums looking for answers to this and found many things to try none of which ended up working in the end.

Among other things, this is what I tried.

  1. Verified Ruida PWM using a DVM at pins “Ground” and “LPWM1” (verified the same readings on LPS at pins “G” and “In”).
    1% PWM = 0.04v
    25% = 1.2v
    50% = 2.45v
    75% = 3.7v
    100% = 4.87v
  2. Verified Ruida Manufactory Settings Min power = 1%, Max = 99%, 20KHz, Glass tube
  3. Turn LPS pot all the way CCW.
  4. Unplugged 6 pin green connector at LPS.
  5. Pressed “Test” button on the LPS (got a reading of 2 mA on the meter).
  6. Turn the pot on the LPS CW.
  7. Every turn or so CW, I would pulse and check the mA reading. It slowly went up to 4 mA.
  8. Heard the pot start clicking but the highest reading I got was 4 mA. Hmmm, that seems low.
  9. Scratched my head and then plugged the 6 pin green plug back into the LPS.
  10. Set the Ruida display power to 10% max, pulse = 4 mA.
  11. Set the Ruida display power to 15% max, pulse = 10 mA.
  12. Set the Ruida display power to 20% max, pulse = 20 mA.
  13. Also 11%,12%,13% = 4 mA, 14% = 6 mA.

If I had more than 10 hairs on my head, I would pull them out. I’m guessing my LPS is faulty but any help on this would be appreciated.

Thanks!!

2

You interpreted it to be linear. These are not linear and maximum power may not be at your maximum mA reading. Keep in mind these are negative resistance devices…

The pwm at 100% should be 5V, but even with 99% pwm, it comes out to 4.95V.

As far as I know, when you unplug all the control connectors from the lps, the test button should lase at 100%, but have never tried what you did exactly. It’s likely limited to the internal pot setting.

If you turned it up, full cw, I’d think it should reflect that in the current reading.

I got this setup procedure from Russ Sadler and have used it with my machine. Had to change the setting a bit when I replaced the tube, but the logic seems firm enough.

Any chance you have a scope available?

:smile_cat:

1 Like
3

Thanks for this reply and all of your other info I have read on these forums (and everyone else’s also)!!

I do not have a scope, I should be able to borrow ours from work.

As it stands, my usable range appears to be 10% to 20% with little to no resolution between the two. I was afraid to go higher that 20% because I assumed it would jump up a large mA amount again and I didn’t want to fry the tube.

I will also probably order another power supply because in all of this reading it seems like having a spare for future troubleshooting would be a good idea. :joy_cat:

Thanks!!!

1 Like
4

That’s about all you can do at this point.

You can try removing the connection between the controller and the lps. Then check the controllers output without a load… Not sure it this will pay off, but it might give us a better idea of where the problem lies.

I think this is a good call. When testing or doing a setup, it’s wise to be conservative in case something unexpected happens.

Let us know what you’ve found…

:smile_cat: