Author Topic: T2 and PWM  (Read 78 times)

GD George

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T2 and PWM
« on: November 30, 2019, 02:29:51 PM »
OK, so I'm not really sure whether or not this is a T2 question.  I have a GearBest 5500mw laser.  I remember that when I set it up, I had issues getting sort of intensity control beyond "on" and "off". I think that the issue was that the laser itself didn't  support modulation. Or is it the card?  Is the fix limited to replacing the laser? Is there a software fix through T2?

Zax, I know you've been over this before but I can't find the posts, so please fell free to chime in!

Thanks,
Jerry

Zax

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Re: T2 and PWM
« Reply #1 on: November 30, 2019, 02:55:28 PM »
PWM is supported by the Nano, but older controllers that were setup for Grbl 0.8 or earlier used D12 for the laser control which means on and off only. The newer controllers use D11 so you can modulate the output but of course the laser driver must be compatible. The latest machines have a TTL output on the controller and a corresponding TTL input on the laser driver, these produce the best power control. T2Laser offers velocity mode and dithered, both of which simulate the grey scale output you can achieve with a TTL system.

If your controller and laser have 3-pin connectors (power, ground and signal) then you have TTL control. T2Laser supports TTL/PWM or non-PWM systems.

GD George

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Re: T2 and PWM
« Reply #2 on: November 30, 2019, 07:34:53 PM »
PWM is supported by the Nano, but older controllers that were setup for Grbl 0.8 or earlier used D12 for the laser control which means on and off only. The newer controllers use D11 so you can modulate the output but of course the laser driver must be compatible. The latest machines have a TTL output on the controller and a corresponding TTL input on the laser driver, these produce the best power control. T2Laser offers velocity mode and dithered, both of which simulate the grey scale output you can achieve with a TTL system.

If your controller and laser have 3-pin connectors (power, ground and signal) then you have TTL control. T2Laser supports TTL/PWM or non-PWM systems.

Thanks Zax!  OK, questions: 
  • When you talk about the "controller," are you talking about the card on the laser as opposed to the card with the Nano on it?
  • A photo of the card that I have is attached. I think that you're telling me that I have the old type, as the laser connector is two-pin?
  • So, if the laser is set up for this card (two-pin), enabling PWM is not possible, and if I really want to go that route, the answer is to replace both.
  • If I have to replace, I needn't go with the 5500MW.

Thanks,
Jerry

Zax

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Re: T2 and PWM
« Reply #3 on: December 01, 2019, 04:30:26 AM »
1. The picture (your Eleks L7 board) is the controller, it uses a MOSFET and 2 wire laser so technically could do PWM but I don't recommend it
2. It isn't one of the old D12 boards, it still uses D11 but drives the MOSFET so the PWM signal is 12VDC and not TTL (5V).
3. To achieve the best results you would need to replace both the controller and laser module.
4. You could use any power diode you choose. The 2500mW are what I prefer as they work well for engraving and can cut thinner ply (2mm) with air assist.

GD George

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Re: T2 and PWM
« Reply #4 on: December 01, 2019, 07:17:20 AM »
OK, got it. Thanks Zax.  Is the MOSFET on the laser module itself?

I originally got the 5500mW as I figured "some's good, more's better, and too much is just right."  I'm not sure that's the case though, as this one doesn't really focus all that well. It's rainy today, so will be an indoor day rather than a working-on-the-vehicles day so, I'm going to a few things with the laser, and see if I can get that .dxf file to work better with t2.

Thanks again for your answers!

Jerry

Zax

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Re: T2 and PWM
« Reply #5 on: December 01, 2019, 09:08:03 AM »
In my opinion the 5.5W is too much for the MOSFET without a heatsink and cooling fan.

If you have any questions about the DXF files just let me know, it's easier if you post or email the file to me so I can check it.
« Last Edit: December 01, 2019, 09:08:40 AM by Zax »

GD George

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Re: T2 and PWM
« Reply #6 on: December 01, 2019, 07:03:42 PM »
That picture helps a lot., thanks. That's a teeny-tiny MOSFET. The ones on my printer are much bigger but, then again, I guess they handle more power.  Thanks Zax.


ggallant571

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Re: T2 and PWM
« Reply #7 on: December 02, 2019, 05:44:34 AM »
Good MOSFETs have a very low on resistance. Read the device specs and you may be able to replace it with a more efficient one. The 30 second warning is for the low power switch mode as it operates the device in a partially ON condition. When fully ON or OFF there is much less energy lost as heat. A similar operating circuit exists on the circuit board of the 3-wire units.

T2 (and other applications) have a low power function using PWM.
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