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Messages - a_kent

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1
That's the way it should work, Stonemull! Nice job with the SMD part.

It would also be interesting Koskee, to know why the 1k stops the 3.5 watt laser. It should not. It's just a digital signal going to the laser controller. A scope on the PWM would be interesting to see.

Kent

2
1k is a value that will work with the Laser output of the Mana SE, IF the laser itself does not already have a pull down.

Again, the way to tell, is to turn on the Mana SE with the USB unplugged.

If the laser goes full on, then you need this mod. The laser will also go full on for a second or so when you go to Laser control from the T2 software if you need this mod.

Also, the MOSFET has no bearing on the port labelled 'Laser'. The MOSFET is used for non-TTL lasers on the red port labelled 'Motor'. It switches the low (ground) side of the laser power on this port.

The Laser port PWM control signal is a direct digital output from the Arduino. The Arduino has no trouble driving this signal with the mod.

Best,
Kent

3
The MOSFET driving the "Motor" port is the problem.

Ggallant571:
The Mosfet used on this board is rated at 10 amps continuous and 35 amps pulsed.
In this design, it is switching the low side of the motor port (ground side).
The gate voltage threshold is from 1 to 2 volts (Vgs), and is rated for logic levels.

So in this design, it is well implemented.

I have attached a datasheet for the part.

Kent

4
Thanks for the pictures.
Where do the wires go and for what purpose?
Thanks.

The wires on there are to some kind of limit switch as mentioned by Pascalp, and are not a part of this fix.
I have not looked into that mod.
Kent

5
Note that with the Mana SE, the Mosfet does not go to the laser port.
It only goes to the low side of the motor (red) port.

The PWM signal on the laser port comes directly from the Nano.

I have a feeling that either the Nano or the laser module itself have a problem.

Kent

6
EleksMaker Mana SE / Mana SE laser issue...
« on: March 01, 2017, 12:57:35 PM »
Issue: The Mana SE leaves the Laser PWM signal floating.

This is not an issue when the Nano is actively driving it, but it is when the USB cable is disconnected and when the Nano is booting up and any other time the signal is left floating, such as when T2L goes into Laser control mode.

I read in the other thread where Zax is using this board with a 2watt laser module that does not turn on when the PWM signal is open. Apparently, this Laser module includes a PWM pull down.

I have two laser modules, one 2.5watt and one 3.5watt that both turn on.

The fix for the 2.5 and 3.5 watt laser (and likely others) is to solder a 1k ohm resister between the laser PWM signal and ground. The PWM is the 'S' signal on the connector. Ground is the center pin.

Note that this fix is also needed if you are using the red motor port. This same signal also drives the low side of the motor port through a Mosfet.

Best,
Kent

7
@a-kent - I consider it more than an engineering oversight. The entire MOSFET drive circuit is deficient. Each MOSFET has has definitive current and voltage requirements to reliably turn fully ON/OFF in a specified time. The AVR328 I/O pin barely suffices. I have 2 cheap NANO clone boards that generate less than 4.2V for a logic high and they cannot fully turn the MOSFET ON. The result is excessive heat. Eventually (2 minutes) they get stuck in the ON state and melt the PCB trace.

I have posted before and some users say my analysis is wrong. I contacted the MOSFET manufacturer and they agree with me. My boards now contain dedicated MOSFET driver chips. They work reliably and run cool with 3.3V ARM processors.

Perhaps there are power MOSFETs that do work with 5V logic. IMO - This circuit is something that a legitimate engineering department would investigate and make rock solid before releasing onto the consumer market.

@ggallant571, mine (Mana SE) has a single Mosfet to drive the motor's low side on the red connector. I don't see a problem there.

My board does not have a Mosfet driving the Laser. It is a signal directly from the Nano. The same signal also drives the servo port.

Pascalp, that is perfect!
Kent



8
T2 Engraving / Re: T2 laser comes on when going to laser control.
« on: February 27, 2017, 02:12:02 PM »
And a HUGE thank you to Zax for the offer of sending a Nano board to me!!

9
T2 Engraving / Re: T2 laser comes on when going to laser control.
« on: February 27, 2017, 02:08:57 PM »
Well, it's fixed!
It really is the simple issue of a floating signal. I also consider this an engineering oversight.

If any of you have a Mana SE, you can easily see if you have this issue.
Put your glasses on first!!
Turn off the power to the board.
Unplug the USB cable from the Nano.
Then turn on the power to the board with the 12v supply plugged in.

On mine, the laser would go to full on and would stay there.

Mine would also turn on the laser when you first turn on your computer if you turn on the machine first. It would also turn on when you go into laser control mode from the T2 software.

To fix this, I installed a 1k ohm pull down onto the laser signal on the large board.
(Solder a 1k ohm resister between the 'S' signal and the center ground signal on the laser connector.)

Any resister value >1k is not enough.

On mine, this left the float at about 0.4 volts. When it is floating after power on, there is a very low level light from the laser, about like pressing the button on the laser module.

Also if anyone is using this board for driving a motor on the red connector, this same signal goes to the gate of a Mosfet that controls that motor. It will come on the same way the laser does without this pull down.

Best!
Kent

10
T2 Engraving / Re: T2 laser comes on when going to laser control.
« on: February 26, 2017, 06:02:18 PM »
The design is not public. I reverse engineered the L7 & L8 controllers and posted the schematics on this site.

It is somewhat odd that not all systems behave this way. The the signal used for laser ON/OFF control is floating during reset but should not provide sufficient energy to turn the laser on. I suspect a pulldown resistor might might help. It is also possible that the boot firmware on some boards is driving the signal high.

IMO, the solution is to add hardware with an ENABLE signal (with pulldown) from a completely unused I/O pin.
 

Hi GG:
That is great that you were able to reverse engineer those things.

NO SIGNAL should ever ever be left floating!!! Rule in my camp. To many things can happen to that signal. All bad.

I have seen signals left floating where a new silicon revision caused a state change at any given point!

While I have no clue yet why this signal is doing what it is, I hope to find out.

I do know from past Atmel designs that you can program pull ups and pull downs in the firmware fuses. I think this is an Atmel processor used here, so yes, you can affect the hardware with the boot code and firmware, possibly.

Kent

11
T2 Engraving / Re: T2 laser comes on when going to laser control.
« on: February 26, 2017, 05:15:40 PM »
Yes and yes.

12
T2 Engraving / Re: T2 laser comes on when going to laser control.
« on: February 26, 2017, 05:11:57 PM »
I would be very interested in seeing what Carolynsdad found out!

I'm also a retired EE, so I can do things.

I do have the GRBL source tree. I have not scrounged for schematics on this design, although I seem to remember that it's all public domain.

Thanks!
Kent


13
T2 Engraving / T2 is awesome!
« on: February 26, 2017, 05:01:45 PM »
I bought T2 yesterday and have been having a blast with it!!

I have engraved some photos now, and they turned out much better than I expected.

I have attached one of my daughter on some fairly rough plywood. I know it could be better. I'll be tweaking everything as time goes on.
This is actually my first image after buying T2!
I used greyscale, speed of 1000, 0-255 power overridden in the output screen to 70%.

I have also done some sketches with text and graphics.

The only minor issue I have had is mentioned in the other post about the laser coming on during the transition to laser control.

I initially used the Benbox and Elekscam software. Those are not so good, to me.
I then found the T2 package from this forum. I played with the software for all of 10 minutes and bought it!! It is awesome!

My machine is a Banggood A5, 2500mw, with the Mana SE board, running GRBL 1.1E firmware.

Kent

14
T2 Engraving / T2 laser comes on when going to laser control. SOLVED!!
« on: February 26, 2017, 04:44:12 PM »
When going from the main editing screen to the laser control screen, the laser comes on full for a couple of seconds.

This is startling and puts a mark on the board. I also am not in the habit of putting on the goggles until I hit 'go'!

I am running the A5 2500mw Banggood machine with the Mana SE board, with 1.1E firmware and T2 version 1.3W registered.
I have had it running only for a couple of days.

Is there a way to stop the laser from coming on like this?

Regards,
Kent


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