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M-140 diode death?

rusirius

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Why would a laser driver need to take take "step and direction commands" ? Isn't that just needed for your stepper motor drivers?
Because in doing so it's very easy to burn a grey scale image. You can rasterize a grey scale image and plot the "depth" (if using z-axis, or any other axis if not) based on how dark a particular pixel is. By doing so the gcode will be a little bit like a bump map, but the result is being able to burn out an almost perfect grey scale representation of an image with incredible accuracy.

Here's an example of an image burned into poplar, not my work obviously, just someone using the exact same technique.

 

Joelaw

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Rhd,

The above post said it all. I am using software called PEP4 to generate g-code of an image that will produce pictures on wood etc.

I have a 2' X 4' CNC router and have mounted a Laser onto the head. The controller adjust to laser power between 0 and full power depending on the code sent (between 0 and 255). It scans back and forth each line burning each pixel based on the density of the b&w pixel. Works pretty well when everything going OK. Not so much when you have Laser burnouts.

There must be a lot of people doing this on this forum, I just did not look very long before posting to this thread. I will have to keep looking. Anybody point me in the right direction?

JoeLaw
 
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In other words, it needs to interface with
CNC hardware.

Almost any driver can be adapted, though if
you already have the Arduino set up.
 

rhd

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As you guys may have seen, I ordered the Banggood laser "engraver". It's not here yet, though I doubt it has this functionality. I bet it's monochrome.

If you guys will keep it all open source, I would be happy to contribute to a project with a goal to produce an open source grayscale CNC laser router.

I have a huge number of drivers that already work, happy to build off those for the laser driving aspect. I assume you guys have the schematics for whatever interfaces with the PC and runs the motors? For a long time I've thought it was crazy that there weren't any open source laser CNCs on this forum.
 
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Joelaw

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Rhd,

I don't mind open source at all. I try to use all of the open source stuff that I can find. I just couldn't find anything that I needed for the job.

I am using a CNC program called MACH3 to output g-code to an ethernet control board, then it goes to the breakout board through opto couplers to the motor drivers and to my board. The pulse rate of the step is about 3-5us wide and runs in 2ms per step. The direction pin is either high (5v) or low depending if it is supposed to move up/dn, left/right or whatever. I am also using another output to enable the whole thing to prevent unwanted output.

The arduino just counts the pulses and either + or - for direction of count. It is enabled with a command from MACH3 to output or not. I think that the enable pin is a must to prevent the laser coming on when not being told to. In my case, the Arduino ouputs a PWM signal based on the value of the count from zero to 255. That goes to the Maxium board that controls the output current from zero to max current, in my case set to 1.5 amps.

Using this means that I do not have anything like an X-drive on the diode since the current varies from the Maxium board control.

Before this project started, I used a current limiter and a fet output to turn on or off the laser. Of course this works for just engraving artwork but cannot give me lighter or darker spots needed for a gray scale type picture.

I am not trying to invent anything just get something working for this purpose. I thought that an all electronic solution was better than a mechanical motor driven encoder like others were using.

It is getting pretty expensive with all of the laser diodes I have killed.

More satisfactory solutions would be greatly appreciated by a lot of people. This addition to my router has produced some very good results and lots of fun. I have used my router much more to burn wood than cut wood.

If anybody can post what they are using for a project like this I really would like to know.

Please let me know if I can help in any way.

Thanks,

JoeLaw
 

rhd

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I don't believe the Max board would vary the current. That's the whole point of PWM with LEDs or LDs, it goes full current, but varies the duty cycle.

Wouldn't make sense for it to operate the way you've described, because you'd see no output for many of the lower values in the 256 scale due to lack of threshold current.

Why don't we take the Max IC, and build a more durable driver schematic / PCB that will work with other stock components. I assume it needs to be controlled by an Arduino nano?
 

rusirius

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I don't believe the Max board would vary the current. That's the whole point of PWM with LEDs or LDs, it goes full current, but varies the duty cycle.

Wouldn't make sense for it to operate the way you've described, because you'd see no output for many of the lower values in the 256 scale due to lack of threshold current.

Why don't we take the Max IC, and build a more durable driver schematic / PCB that will work with other stock components. I assume it needs to be controlled by an Arduino nano?
Exactly, the max chip I'm using (max5451) is a "stepable) digital potentiometer. So it lends itself very well to doing analog modulation of the laser power.
 

rhd

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Exactly, the max chip I'm using (max5451) is a "stepable) digital potentiometer. So it lends itself very well to doing analog modulation of the laser power.
No, that's not what I mean.

At say 25 / 256, you're expecting something like 150mA right? How much output power do you think that will give you from an M140 ?

Probably none.

Also, how are you interfacing the MAX5461 with the buck IC? I assume you're not using it directly as a sense resistor because it surely can't handle that current. So in wondering if you're using a current sense monitor IC as well?
 
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rusirius

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No, that's not what I mean.

At say 25 / 256, you're expecting something like 150mA right? How much output power do you think that will give you from an M140 ?

Probably none.

Also, how are you interfacing the MAX5461 with the buck IC? I assume you're not using it directly as a sense resistor because it surely can't handle that current. So in wondering if you're using a current sense monitor IC as well?
No, I will use the max to feed an opamp. That will result in a0-5v output. That voltage feeds into a laser driver that supports analog modulation. It has a zero bias, meaning atty 0 volts it can be set just at the point where the diode begins to lase. Whatever power you want to set it at. The rest of the curve up to 5v is scaled to 5v, so 5v is max power, 0v is whatever you want minimum power, and the max is used to divide that curve into 256 steps.

Does that make more sense?
 

Joelaw

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Rhd,

You are right again. The max output is a pulsed PWM and I have a min and max setting to make sure that the min turns on the laser and max gives me the best burn without overburning the spot. I usually start about 30 min and 200 max.

I scoped the output last night and there is a lot of noise when it is on. I guess that this project using the max16820 is about done in. It seemed simple when I started but obviously there are many more issues to consider.

The Arduino Nano seems to be an easy way to control the signals. I looked up your Banggood laser engraver last night and it is using a Nano controller. It also states that it can output gray scale. I want to know what you find when you get your unit.

It sounds like Rusirius already figured everything out. All that has to be done is incorporate it all into one easy to build unit.

JoeLaw
 

rusirius

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I'm not home this weekend, but when I do get home I'll try to post up everything I have. I'm building with openbuilds vslot. As for control, I may end up building a board with an atmega running grbl, or possibly a machine running linuxcnc, but for now I'm going to try to use the cnc xpro, another open source build.
 

rhd

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Rhd,

You are right again. The max output is a pulsed PWM and I have a min and max setting to make sure that the min turns on the laser and max gives me the best burn without overburning the spot. I usually start about 30 min and 200 max.

I scoped the output last night and there is a lot of noise when it is on. I guess that this project using the max16820 is about done in. It seemed simple when I started but obviously there are many more issues to consider.
Don't give up on it just yet.

This is what it looks like?


Try swapping on this inductor (it's a bit larger, but I believe it will still fit your pads):
SRN1060-470M Bourns Inc. | SRN1060-470MCT-ND | DigiKey

Then, at C3, add this:
C3216JB1C476M160AB TDK Corporation | 445-11695-1-ND | DigiKey

Then, remove C2, and add this:
C3216JB1V226M160AC TDK Corporation | 445-11739-1-ND | DigiKey

Give that a scoping. I think you'll find the ripple dramatically reduced.
 
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Joelaw

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Guys,

Sorry but I had a small problem Saturday and had myself a heart attack. After a quick catherization on one spot. I am now in the hospital waiting for bypass surgery on Tuesday. The doc said I cannot go up or down stairs for four weeks so that means I cannot work on my laser for a while.

I will keep watching and seeing what is happening though.

Thanks again for all the help, this is a good fourm.

JoeLaw
 




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