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Just starting

Posted by kd6hq 
Just starting
December 10, 2017 01:46AM
I'm just starting to read about lasers.
I've been looking at adds and ran across one ( [www.ebay.com] ) I'm curious about.
This add only shows a 12 VDC connection and nothing for TTL or PWM.
So I'm guessing that the laser is meant to be used at full power all the time.
Wouldn't this shorten the life of the laser?
thanks

[www.ebay.com]
VDX
Re: Just starting
December 10, 2017 10:54AM
... yes, the "lifetime" degrades when driven constantly at max. values or even "overdriven", what many chinese driver do, to rise the output power eye rolling smiley

Another problem could be (TTL- or PWM-) switching the diodes with a cheap driver (or using LED-drivers for laser-diodes), what's often generating high current spikes and too can drastically reduce the lifetime ...


Viktor
Re: Just starting
December 15, 2017 12:28AM
I love these useless fan cooled heatsinks! There are fins outside the housing, but the fan tries to suck air from the inside...and there are no air gaps at the bottom! LOL
VDX
Re: Just starting
December 15, 2017 01:11AM
... this is exactly "the other way round" - no fins on the outside winking smiley

[www.lasertack.com]


Viktor
Re: Just starting
December 16, 2017 03:32PM
One of the problems with watching utube videos is that most of them do not give enough information. I ended up purchasing the laser that I provided the above link for.
The video I watched showed the laser power wires simply being cut and attached to the D9 terminals of a RAMPS 1.4 board. No other inputs are available on this
specific laser module. No PWM or TTL. D9 on the RAMPS 1.4 board is used for 1 or 2 purposes. First it can be configured for a second extruder or for pwm fan use.
When setup for pwm usage it can provide a varying voltage output up to 12VDC or the output of you power supply. For instance the power supply I use actually
puts out 14.3VDC so in this specific case the voltage varies from 0 to 14.3VDC. I will be adjusting the voltage back to 12VDC.

I have been using a piece of cardboard to experiment with. Using the D9 connector I sent different PWM values from 032 to 255 in increments of 032. Each time I
incremented the value I took a voltage reading and checked the cardboard for a cut mark. I did not notice any cutting until I reached a pwm value of 192 and a voltage reading of 11.4vdc.
From 192 - 255 the cut mark went from a very light burn mark to 255 where the first layer of cardboard was cut thru.

Further experiments showed that I could cut thru a 1.5mm medium hardwood with about 5 layers of cuts incrementing 0.2mm with each layer.

I next tried doing some Raster print using wood. As you might expect it did not come out very well. I suspect that this was because of the low pwm settings generated
in the gcode. The "S" settings ranged from S3 to about S255. Since the laser did not print until it reached a pwm setting of S192 (+/- a little) all the S settings blow S192 did not print.
So shades of gray did not work properly. If it would have been a black / white print as in a pcb it would have been fine.

So from a beginners point of view; if you want to just do black / white (pcb) prints or engraving this module should work ok. But since I also want to do Raster prints
I will need a module that has separate 12Vdc (constant current) plug as well as either TTL or PWM connection.

*Readings that I took.

PWM, Voltage, Burn mark
032, 2.33, no
064, 4.09, no
096, 6.20, no
128, 8.08, no
160, 9.80, no
192, 11.4, very light
224, 12.8, dark
255, 14.3, cut thru 1st layer

* All reading were taken with DVM so readings are average not peak.

Now back to my reading.

Edited 1 time(s). Last edit at 12/16/2017 03:38PM by kd6hq.
VDX
Re: Just starting
December 16, 2017 04:47PM
... you'll need a better driver for the diode - I'm supporting my drivers with voltages between 8 to 10 Volts and currents of max. 90% of the rated "max current" -- this can be from 1,1 to 3 Amps for the different 445nm-diodes, and up to 8,6Amps for the IR-diodes.

The controlling modes can be different - either "velocity-synchrone" pulsing or analoque power controlling ... but then too with adjusting the analogue voltage to the speed to prevent excessive burning at line start/end or in edges.

So this is a bit more complex than simply wiring two wires and switching the power per PWM ...


Viktor
Re: Just starting
December 17, 2017 03:12AM
Well I guess I will need to take this unit apart to find out which diode is being used.
Unless someone happens to know which one it uses?
Re: Just starting
December 18, 2017 05:03PM
Why did you buy this laser?
When people advised to get a laser
with a separate driver / supply with TTL control.

Sort of like --- read, watch youtube and ignore it all

This forum may help a lot --- sorry you may have to
do some searches / reading

[www.shapeoko.com]

J-Photonics
expensive but very good, safe, well documented lasers

documents are free for the reading

[jtechphotonics.com]

Please safety - protect your eyes -- it doesn't hurt -- just ruins your vision

Do it right mechanically, Electrically and you won't have to spend over and over
to get some laser engraving done

confused smiley
Re: Just starting
December 20, 2017 10:17AM
To answer your question I bought this laser because I watched a video that showed how to use it with a RAMPS board. The video showed the laser being powered by the fan terminals (D9) on the ramps board. I now know that although this sort of works, it does not work to the lasers full potential. It will do some things but not as well as it could if the current and pwm signals were separated. So I guess you could say that the video was somewhat misleading.

Thanks for the link to Shapeoko. I have never seen that one before. Perhaps because I'm not interested in routers. I am aware of them but have never considered purchasing one. From what I can tell most seem to use TTL level controls while I'm interested in PWM mode. That is because I use RUMBA and RAMPS boards, which both use PWM at 12V or 5V is you want to move pins around in the firmware.

Yes I agree with you I have looked at J-Photonics before. They are expensive and since I'm just experimenting I did not want to spend that much. Especially since this is just a hobby, if it were a business, then I probably would have purchased a pre-made unit from the start. Although if my hobby interest grows I still might purchase one from J-Photonics.

I'm not an expert in any of this, just a hobbyist. I have more fun solving problems and in putting things together than I do in actually using the gadget once it's finished. Perhaps that is why I'm always changing stuff, trying new things. It seems like once they work I move on. I have to say that lasers intrigue me a little more than usual. Perhaps because they can be used on so many different materials. Anyway enough of my rambling.
Have a good day and enjoy your self and try not to take thing too seriously. smileys with beer
VDX
Re: Just starting
December 20, 2017 01:01PM
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...


Viktor
Re: Just starting
December 20, 2017 01:17PM
Quote
VDX
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...

That has given me an idea. For several years, RepRapFirmware has provided a facility to set a specified PWM value on an output pin whenever extrusion is supposed to be taking place. This is typically used for laser engravers. Perhaps we should adjust the PWM value so as to be proportional to the movement speed. What do you think?


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Just starting
December 20, 2017 02:38PM
Quote
VDX
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...

So TTL then, do you have a particular controller that you like?
Since I don't have any right now.
Re: Just starting
December 20, 2017 04:05PM
Switching a Laser diode power ON/OFF is rough on diode

Using PWM on trigger circuit much better
You may be able to gin up a circuit to trigger your laser

I showed you shapeoko laser area which has a lot on
lasers mounted instead of spindle
Shapeoko use GRBL board on Arduino
so PWM out of pin 12 may be used to control laser

since RAMPS is on arduino so you can use a pin
on arduino to PWM the laser

confused smiley
Re: Just starting
December 20, 2017 11:26PM
Quote
dc42
Quote
VDX
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...

That has given me an idea. For several years, RepRapFirmware has provided a facility to set a specified PWM value on an output pin whenever extrusion is supposed to be taking place. This is typically used for laser engravers. Perhaps we should adjust the PWM value so as to be proportional to the movement speed. What do you think?

IMHO that wouldn't work for gray scale engraving? Except you'd allow a PWM-value read from gcode and then vary it according momentary speed.
VDX
Re: Just starting
December 21, 2017 05:37AM
Quote
dc42
Quote
VDX
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...

That has given me an idea. For several years, RepRapFirmware has provided a facility to set a specified PWM value on an output pin whenever extrusion is supposed to be taking place. This is typically used for laser engravers. Perhaps we should adjust the PWM value so as to be proportional to the movement speed. What do you think?

... changing PWM values needs time, what's interfering with the pretty tight syncing for precise engraving - I'm changing the pulse-ON times for engraving with the diodes between 5µs and 50µs (up to 300µs for slow cutting).

So why rise the complexity to generate short varying PWM-sequences, when you get perfect synced pulses form the software meant for the extruder motor stepping (above 300kHz with Marlin4Due) ?


Viktor
VDX
Re: Just starting
December 21, 2017 05:43AM
Quote
o_lampe
Quote
dc42
Quote
VDX
... if you want acceptable engraving/marking results and faster movement than 10mm/s, then PWM wouldn't be the way - with contsnt PWM and accelerated moving the start/end of lines will burn much more than the constant speed part.

Best methode for 3D-printer electronics+firmwares is to use the extruder driver steps, as they are calculated per distance, what's independent of speed ...

That has given me an idea. For several years, RepRapFirmware has provided a facility to set a specified PWM value on an output pin whenever extrusion is supposed to be taking place. This is typically used for laser engravers. Perhaps we should adjust the PWM value so as to be proportional to the movement speed. What do you think?

IMHO that wouldn't work for gray scale engraving? Except you'd allow a PWM-value read from gcode and then vary it according momentary speed.

... you can "dither" BW-images to get a similar "analogue" effect by varying pixel-densities.

For real analogue engraving you have to change the laser power according to the grey value in the image, what's another methode than pulsing. I did this with "pixel-frequencies" of up to 60kHz with an ArduinoDue "synchronous" reading raw image data from a SD-card to engrave high density images for flex-print applications ...


Viktor
Re: Just starting
December 22, 2017 01:40AM
Well this has gotten way over my head, best I go back to just printing.
thanks
Re: Just starting
December 22, 2017 07:34PM
PWM laser action

[www.youtube.com]

Engraving of calibration scale by PWM 1.75W laser
PWM input to laser TTL trigger,
wider (longer) the pulse width the more power, more burning

This is a raster scan of calibration scale

confused smiley
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