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Beginners problem.

Posted by erniehatt 
Beginners problem.
November 08, 2016 04:51PM
I have just built my very first laser engraver/cutter.
I have a 2.5 watt laser, and I don't seem to be able to control the power, it just cuts straight though thin paper, not so much cutting through but just burning a hole. It engrave ok on MDF board.
I am using inscape , J tech Photonics laser tool and universal gcode sender.
Any special settings I need to make to be able to engrave on art paper and to cut stensils for air brushing. Thanks for any help you may be able to give.
I am not after someone doing the work for me, just a guide as to where the changes need to be made. Ernie

Edited 1 time(s). Last edit at 11/08/2016 08:42PM by erniehatt.
Re: Beginners problem.
November 09, 2016 01:08AM
To control power you need PWM compatible laser driver.

Regards
Re: Beginners problem.
November 09, 2016 01:41AM
to be honest I would not have a clue as to what driver it has, it came as a package, with laser heatsink and fan.
I runs at 12v 2 amps, that's all I know
Re: Beginners problem.
November 09, 2016 02:28AM
It has constant current driver built in ON/OFF only

Regards
Re: Beginners problem.
November 09, 2016 02:31AM
So as it stands, it's just about useless.
Re: Beginners problem.
November 09, 2016 02:44AM
You can get PWM driver [www.ebay.co.uk]
and remove internal driver to be able to drive with new one

Regards

Edited 1 time(s). Last edit at 11/09/2016 02:46AM by rastaman46.
Re: Beginners problem.
November 09, 2016 09:54AM
Thank you for giving us specific information on your build
so we may help you
Type of laser --- arduino hook up etc

and you have your laser eye protection ON.


JTech Photonics is a good resource

[jtechphotonics.com]

Inkscape Laser Plug-In
Using the Inkscape Laser Tool Plug-In

[jtechphotonics.com]

confused smiley
Re: Beginners problem.
November 09, 2016 11:51AM
Thanks for the link, just how difficult is it to make the necessary changes.
I am not a technician of any kind, just a hobbyist.
Re: Beginners problem.
November 09, 2016 10:05PM
Quote
erniehatt
Thanks for the link, just how difficult is it to make the necessary changes.
I am not a technician of any kind, just a hobbyist.

What Laser machine do you have? (link or pic)
What laser do you have connected? (link or pic)
What hardware controller are you using?
What firmware is running on the controller?
Have you read through Jphotonics web site?
Do you understand it?

To control the power you need to know what pins the laser is connected to.
You then need to issue the correct G-Code command to control that pin which could be something like
M3 S255

M3 is the connection pin in the software ( you need to change this if the laser is connected to a different pin.) and S255 is the power setting and goes from 0 to 255 and is the setting you need to change.

This could be done in the pluging or may need to be altered in the gcode file with a text editor before you send it to the laser.

Edited 1 time(s). Last edit at 11/09/2016 10:06PM by GRAYWOLF.
Re: Beginners problem.
November 10, 2016 11:49AM
Thanks Greywolf,

The laser machine, is homebuilt.
The laser I don't know to much about, so I can only give you what was on ebay.
The controler is an Arduino Uno and a CNC shield, the firmware is GRBL latest version.
I have a logic mosfet module for switching the laser.the laser connects to that,
from there to the Z endstop socket, not sure which pin on the Uno that is.
The laser is manually adjusted up and down over a distance between 60 and 160 mm,
may look later into adding a Z axis
I have copied the Jphotonics pages, but have not completely gone through them as yet.
I have looked at the gcode and the code is M03 S0-255, I have gone through and altered
the figures, but it made little if any difference.
On a hard surface it engraves beautiful, but with thinner materials no matter what colour
it just burns it completel out.


The only info on the laser is what was on ebay.

Description:
Heatsink Material: aircraft aluminum
Output Power: 2500mW(2.5W)
Wavelength: 445nm(blue laser)
Voltage: DC 12V
Current: 1.3A
Beam Shape: dot(focusable)
Life Time: >10,000 hours
Working Temperature: -40-75?

Feature:
445nm 2.5W focusable blue laser module
DC 5.5*2.1 power port
Aircraft aluminum heatsink with cooling fan ensure long working time continuously
Equipped with constant-current driver board ensure stable output optical power,
low heat no external driver board needed,easy to use
Suitable for industrial laser engraving machine equipment usage.

PS. I think that the laser could be connected to pin 12.

Edited 2 time(s). Last edit at 11/10/2016 12:18PM by erniehatt.
Attachments:
open | download - Laser.jpg (44.5 KB)
open | download - P1030586.jpg (175.6 KB)
VDX
Re: Beginners problem.
November 10, 2016 01:04PM
... with my modules I'm setting the max. possible power by adjusting the current to around 90% of the nominal power (e.g. 1,5A instead of the nominal max. 1,7A of the blue 2W-diodes) - but the "effective engraving power" is then defined by specific pulse-length for the emitted pulses -- what's with the 2W@445nm-diodes mostly in the range from 5 microseconds (only "marking" cardboard with up to 100mm/s) to 400 microseconds (cutting through and then much slower moving speeds, so the pulses won't overlap).

To get this working, I'm either using the X/Y step pulses as source for the laser-pulses with common CNC-controllers, or the extruder E-step pulse with RepRap-electronics -- so it's generating speed-independent pulsing, what's essential for constant engraving power over complete lines without "accelerating-artefacts" ...


Viktor
Re: Beginners problem.
November 10, 2016 02:08PM
Hello Victor,
Lets see if I have got this, my knowledge on it is limited.
It seems I have got my laser connection wrong, you say connect it to X/Y step pulse, I have been looking around for info and have found that some use the Z pulse step, is this the same thing.
Adjusting the current, would I be needing an additional power source for the laser, at present I am using the same supply for everything.

Ernie

Edited 1 time(s). Last edit at 11/10/2016 02:12PM by erniehatt.
VDX
Re: Beginners problem.
November 10, 2016 03:43PM
Hi Ernie,

using Z-step or -dir is only for simple ON/OFF switching, where you activate the laser for drawing a line and switch it off, when line ends.

With this methode you'll get the previously mentioned "acceleration artefacts", where slower moving at start and stop of the line will burn more, while faster speed along the line will burn less ... so you have to engrave or cut pretty slow to avoid any acceleration or speed changes.

For engraving with constant "burning power" along lines you either have to adjust the laser power synchrone with speed changing, or use a "speed independent" methode.

I've developed a "XY-step-pulsing hack" with my first laser-cutters around 1986, where every step pulse from either the X- or the Y-axis-driver will generate a laser pulse, so the effect is not related to speed, but to step resolution only.
You can find some infos about this and more here, @ "6. controlling the output-power:" - [www.reprap.org]

Maybe even simpler is to use the extruder-motor step pulses of a 3D-printer electronic - the software calculates the extruder speed synchronous with the print-head moving ...


Viktor
VDX
Re: Beginners problem.
November 10, 2016 03:51PM
... adjusting the current is done inside the driver - most laserdiode drivers are built around a constant current driver, which will set the maximum power, and then a modulation circuit, which either only switch the current ON/OFF with an input signal of 0V/5V, or reduce the current accordingly with an analoque voltage between 0-5V or a PWM input signal, which is averaged and read as analogue.

If you can use the same PS depends on the needed current or if you'll need EMI filtering - my drivers are connected to 12V and needs currents of up to 10Amps while fast switching the current with up to some ten kHz, so I'm using a separate PS with good filters to avoid EMI problems ...


Viktor
Re: Beginners problem.
November 10, 2016 04:40PM
Thanks Victor,
Had a look at the link on the previous post, And I could make a board for that.
I have to get my head around this..
1) I see it runs off of 5v fine, they should not affect the 12v needed by Laser, I think not.
2) connections, I see it connects to either X or Y step, the bit I am not understanding is where the laser fits, is that connected to JP3 pulse, is so where does the 12v laser power come into the equation
3) would this eliminate the Mosfet circuit, I think it will..
Re: Beginners problem.
November 10, 2016 06:03PM
Read
TTL modulation help needed
[forums.reprap.org]


It appears that you just have a laser head?

What brand laser?
ask seller to sell you a driver for laser.
angry smiley

Usually
12V high current main supply to laser --- conditioned down to 3.3v constant current diode supply
and
a trigger circuit to turn diode ON / OFF properly

forcing the diode supply ON / OFF NOT the way to do it.

confused smiley
VDX
Re: Beginners problem.
November 11, 2016 01:46AM
... yes, switching the PS ON/OFF to modulate the laser is a bad idea -- this will generate heavy overcurrent "spikes", what's drastically reduces the diodes lifetime.

A proper constant current driver "receives" the 12V voltage from the PS, but regulates on his own the output to a set current through a shunt resistor.

The laserdiode is set in series with this shunt resisitor, so will get the same current.

The current modulation is mostly made with a MOSFET, switching the voltage+current through the laserdiode and the shunt resistor.

Now the "trick" is to regulate the current to the set value without "overshoots", and when switched OFF, without "undershoots" too, as they will cause even more damage to the laserdiode.

Cheap constant current drivers with puffering capacitors (used to stabilize the voltage output) aren't optimized for fast ON/OFF modulation, so either won't switch faster than some Kilohertz, or too emit short overcurrent spikes with up to some Amperes above the set value, before reulating it - this is only seen with Oszilloscopes, but will kill the laserdiode after some hundred hours (while with a good driver the expected lifetimes are more in the hundred tousand hours)

Better common drivers with fast regulating can be switched with up to 100 kHz with much lower "overshoots" with only some ten Milliamperes.

As I'm modulating my lasers with up to 1 MHz and currents of up to 20 Amps, and laser-drivers in this category are pretty expensive (some thousand USD), I've started to build my own ones.

Now I'm developing laser-modules in my day-job, so this is job-related know-how under NDA's -- so can't go more in detail, than sketched here eye rolling smiley


Viktor
Re: Beginners problem.
November 11, 2016 03:00AM
Thanks
Cosmicray, the info I have on the laser is posted earlier in the piece, I have no further info on it.

Ok Victor can we backup a bit to my last post, I feel things are getting away from me, thanks

Edited 1 time(s). Last edit at 11/11/2016 03:01AM by erniehatt.
VDX
Re: Beginners problem.
November 11, 2016 06:11AM
... read the posts in the thread linked by cozmicray - this should be very similar to your driver problem ...


Viktor
Re: Beginners problem.
November 11, 2016 10:31AM
Quote
VDX
... read the posts in the thread linked by cozmicray - this should be very similar to your driver problem ...

Thanks Victor,
I have read that link twice, but must say I am somewhat lost.
I have no wish to go delving into the inners of the laser module, for one my budget does not go far enough to replace it if I break it in any way.
Is there some way I can do this with an external circuit of some kind.
If not I will just have to stick to engraving hard surfaces, until it fails.

If I am reading things correctly, my Mosfet circuit is no good.

Edited 1 time(s). Last edit at 11/11/2016 10:57AM by erniehatt.
VDX
Re: Beginners problem.
November 11, 2016 02:21PM
... you have to identify and understand your parts, so you can find a driver for them with correct infos and documentation ..


Viktor
Re: Beginners problem.
November 11, 2016 02:32PM
Yes Ok,, doesn't help me much does it.
I tried connecting to x/y steps, did nothing, connecting to dir did turn on the laser, so I suspect that's the same as connecting to the Estop.
If identifying my parts mean pulling it apart, at 81 I might as well give it a miss. thank you very much.
VDX
Re: Beginners problem.
November 11, 2016 03:00PM
... the DIR pins changes only when the moving direction of the axis changes, but don't generate pulses.

It seems, the X/Y-pulses of your board are much shorter than the activation time of your laser-driver, so teh laser won't light up -- here you'll need a circuit to make the pulses long enough.

For fixed pulse lengths I'm using 74HCT123 "monoflop" IC's -- for variable pulse lengths to set different powers I'm using small Arduinos which, when Reset, reads the voltage across a trimpot to define the pulse-width for the laser, which will be executed, whenever a short pulse from the controller was received ...


Viktor
Re: Beginners problem.
November 11, 2016 06:16PM
Thank you Victor, can you give me a circuit diagram.
Re: Beginners problem.
November 11, 2016 06:56PM
With the laser diode you have -- you will never achieve anything
Rastaman46 in the TTL modulation help needed thread
started with same laser head without a driver.

You can waste a lot of time trying to get the junk going
or
get a laser with a proper driver that can control it

all the info in TTL modulation help needed thread!

If you can't follow that -- perhaps you shouldn't be PLAYING wit lasers

sad smileyconfused smiley
Re: Beginners problem.
November 12, 2016 11:51AM
Quote
cozmicray
With the laser diode you have -- you will never achieve anything
Rastaman46 in the TTL modulation help needed thread
started with same laser head without a driver.

(You can waste a lot of time trying to get the junk going
or)
No time has not been wasted getting it going, it engraves very well on thick material, it wont just work on thin stuff, which is why I started this thread.and I don't consider I have not achieved anything, I have built it and it does work. I agree with the laser being junk.see scan of my first effort, I call it an achievement.

(get a laser with a proper driver that can control it)

That is good advise, but at the moment it's not in my budget.

(all the info in TTL modulation help needed thread!

If you can't follow that -- perhaps you shouldn't be PLAYING wit lasers)

Please, can you show me where I said I couldn't follow or I didn't understand it.
What I said was that I was not prepared to pull the laser apart, that still stands.

Thank you for your input

:

Edited 3 time(s). Last edit at 11/12/2016 01:57PM by erniehatt.
Attachments:
open | download - img003.jpg (231.6 KB)
VDX
Re: Beginners problem.
November 12, 2016 01:42PM
Quote
erniehatt
Thank you Victor, can you give me a circuit diagram.

... as I've mentioned some posts ago:

Quote
VDX
...
Now I'm developing laser-modules in my day-job, so this is job-related know-how under NDA's -- so can't go more in detail, than sketched here eye rolling smiley


Viktor
Re: Beginners problem.
November 12, 2016 02:00PM
Fair enough Victor.

I may be able to look at a replacement in the new year, any sugestions on what to buy. Thanks
Re: Beginners problem.
November 12, 2016 07:34PM
If you would of read the TTL modulation help thread before purchase
you would be in this pickle -- and wasted money

Look for rig that has a Laser diode head and a driver board.
A driver board that has trigger connection -- so you may PWM the laser.

Look at JTech Photonics web pages.

Constant current supply
adjustable Driver board with trigger capability.

Laser diode with good focusable lens.

Are you wearing red laser safe protection?

Don't want to recommend white cane seller!


confused smiley
Re: Beginners problem.
November 12, 2016 08:00PM
I thank you for the info concerning the lasers.
So I make an error in my choice of diode, even as we age we do tend to make them, I suspect you have made your share.
The safety bit I will ignore, I have been around a long time I have learnt a few things, having built Electronic Gap flashes with capacitors that hold 45k voltage, in fact 3 of them, I am still around.,
Yes I do own the glasses.
I just realized I have and old 0 .5 watt laser that I used to use to trigger my camera for high speed photography, I may have a look at opening it up to see how much of a problem it will be.

Edited 2 time(s). Last edit at 11/13/2016 10:57PM by erniehatt.
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