Author Topic: Pin 11 PWM remains after image completes  (Read 5437 times)

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #15 on: July 09, 2016, 03:34:00 PM »
Well, if my math is correct then 0.004ms should be about .4% power which shouldn't be enough to turn it on. Sorry, I didn't mean to make it sound more than what it really is. I guess its just a mind thing sine it's not 100% off lol.

Zax

  • T2Laser
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3517
    • View Profile
    • T2Laser
Re: Pin 11 PWM remains after image completes
« Reply #16 on: July 09, 2016, 03:59:27 PM »
You have a valid point, it should be off after sending both a power 0 and disable laser command.

I don't think the driver is sourcing any current though, so I suppose it's OK.

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #17 on: July 09, 2016, 04:25:44 PM »
Yeah probably so.

I've been reading up on some PWM controlled current source circuits and that $10 board from bangood.com is sounding better and better lol. I guess I'm loosing my sense of adventure lol.

I took the fan off of my 500mw laser module today and had a look at the board. Its the same as in your picture but mine doesn't have the epoxy in it. It has threads on the inside of the heat sink which leads me to believe the whole unit was screwed into the heat sink. Mine also has the t- and t+ but without seeing the circuit on the other side of the board I'm a bit hesitant to try it. The wires are easy enough to get to and de-solder so I'm thinking I'll bypass the current regulator and drive the diode with the TTL driver mounted somewhere on the outside of the heat sink.


TBN

  • Full Member
  • ***
  • Posts: 104
    • View Profile
    • Traditional By Nature
Re: Pin 11 PWM remains after image completes
« Reply #18 on: July 10, 2016, 03:51:55 AM »
I also use T2 and the firmware provided with it. After a program finishes the laser still produces a very weak light. It is a much lower intensity than the weak light function produces. Clicking the "laser off" icon turns it off.
500mw A5 Mini Laser Engraving Machine from GearBest

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #19 on: July 10, 2016, 04:22:19 AM »
If I'm not mistaken the firmware T2 loads is the j-tech one. Mine appears to be off when it finishes but then again mine doesn't handle PWM well.

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #20 on: July 10, 2016, 04:30:37 AM »
I found a simple circuit that might work with a little modification :) it needs some current and voltage set pots and a filter capacitor on the output. I'll model it up in ltspice and see how it performs:)

Zax

  • T2Laser
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3517
    • View Profile
    • T2Laser
Re: Pin 11 PWM remains after image completes
« Reply #21 on: July 10, 2016, 04:54:31 AM »
Have you been able to confirm if any of the pads on the board are connected directly to the diode?

It would be so much easier to solder to those, than disassemble the module to gain access to the diode pins.

I wanted to make a simple solution, as plug and play as possible so others (who aren't engineers) could follow them. That's why I used the jumper and wire to connect the PWM signal, rather than just soldering to a pad.

So far everything can be done except the diode connection.

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #22 on: July 10, 2016, 06:03:11 AM »
I haven't but I suspect that the L+ and L- that the white wires in your pic are connected to goes to the diode. Honestly I forgot lol but I'll check it out today. I'll see if I can get the board out without damaging it and then we'll know for sure. You are right though, whatever we come up with needs to be something anyone can do.

Does your Eleks board have a row of pins on the right side marked "- + G P"? The reason I ask is because my L7 board does and I think they were added for testing the boards.

- goes to the negative pin on the laser connector at the top of the board
+ goes to the positive  pin on the laser connector at the top of the board
G is connected to ground
P is the PWM pin. I get a nice clean square wave on this pin.

I don't know what all boards have that but that's an option too.


kn4ud

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 753
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #23 on: July 10, 2016, 06:23:32 AM »
I removed the fan again on the unit and was looking at a possible easy way to remove the circuit board and was checking the 2 wires that come through the hole and the best I can tell they do go directly to the Diode. I would like to see what is directly on the other side of the board, if it contains circuit components or just traces.
Allen

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #24 on: July 10, 2016, 06:33:36 AM »
I'm fairly certain it does as my Eleks board does not have any current regulation. 12v going to the diode without current regulation would kill it.

I only have experience with the L7 but I've seen pictures of boards that do have the regulation on the Eleks board.

I'll take my USB microscope and see if I can see the wires connected to the diode through the hole. If I can get some decent shots I'll post the pics.

It would be good to get a good understanding of what each board does and doesn't have. I'm building the schematic for mine and I'll post the files to my Dropbox once it's done.

kn4ud

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 753
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #25 on: July 10, 2016, 06:56:05 AM »
I found this image of what appears to be the board that most of us have ordered. This has a little more detail .
Allen

kn4ud

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 753
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #26 on: July 10, 2016, 07:04:58 AM »
Agastar, do you think current limiting might be handled by a smd resistor on the bottom side of the board? I am very tempted to de-solder all the wires on the board ( or at least the fan and diode) and drag out the Fluke and start checking resistance. This should show if their is a current limiting circuit on this board.
Allen

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #27 on: July 10, 2016, 08:16:06 AM »
I've seen commercial flashlight boards use nothing more than a resistor to drive the LED. However these laser modules come with a 5v power supply if purchased separately but are driven with 12v from the Eleks board (at least my L7 board does). I suspect a simple linear constant current IC is being used.




Zax

  • T2Laser
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3517
    • View Profile
    • T2Laser
Re: Pin 11 PWM remains after image completes
« Reply #28 on: July 10, 2016, 09:02:51 AM »
The L1 doesn't have those outputs, the board is pretty full due to the additional voltage regulator. The L2 has some pads but no pins.

I don't think they would rely on a resistor for current limiting as these laser diodes have significant variation due to temperature. There must be something on the backside of the board, I would have to disconnect the wires to get it out.

Agastar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1878
    • View Profile
Re: Pin 11 PWM remains after image completes
« Reply #29 on: July 10, 2016, 09:32:33 AM »
Does your voltage regulator preserve the PWM signal going to the laser?

I was going to take a look with my USB microscope when I got him today but my laptop is stuck in an infinite startup repair loop after some updates were installed. For some reason it says I don't have any previous known good configurations so I'm down until I get this figured out.