$32 CO2 Laser Controller

[naveenraj]

Hi,
Wow…thank you for this awesome post. It really shows your immense knowledge and research on this topic. Please keep sharing.

[Retroplayer]

Hi,
Wow…thank you for this awesome post. It really shows your immense knowledge and research on this topic. Please keep sharing.

Thank you. I am happy to help. I am not an 'expert' but hopefully I know enough to help some guys out. Rolf seems to be sitting there without a functional laser, so hopefully I can help him get back up and running.

[Retroplayer]

Retro you made me feel a little better that "ours" is better than the one Rolf posted but I would have bought that one if I had seen it.

Sorry about that, mate. I did start out saying This is the one "I" bought. lol

I think you will enjoy the extra torque and speed you get out of those stepper controllers, though. And you will have 3 spares you can put in your 3D printer where the increased resolution might be best served.

From my various projects, I actually just realized that I have about 12 spares of these.

[Rolf_K]

Retroplayer, would you please take a look at this:
RepRap RAMPS1 4 12864 LCD Display Controlle with Adapter Mendel Prusa 3D Printer | eBay
I already have the Arduino ( in my Laos controller) and I don't need that stepper motor drivers, so maybe I could save a little bit of money.
I realize the firmware has to be changed but that should not be a problem.

[Retroplayer]

Retroplayer, would you please take a look at this:
RepRap RAMPS1 4 12864 LCD Display Controlle with Adapter Mendel Prusa 3D Printer | eBay
I already have the Arduino ( in my Lalas controller) and I don't need that stepper motor drivers, so maybe I could save a little bit of money.
I realize the firmware has to be changed but that should not be a problem.

That would be fine assuming you already have the Arduino mega2560 board and stepper drivers. You already have the stepper drivers as well?

[Stigoe]

I think you will enjoy the extra torque and speed you get out of those stepper controllers, though.

You do know that torque and speed goes down as you increase microstepping, right?

[buddydog]

Retro I don't know if you noticed or not but this thread is at 832 views this morning! I looked back a ways but only saw "K40 expectations" really a lot higher than this one. Rolf started something here that has hit a nerve but I think the lighters are being waved for you. How does it feel to have groupies? :-)
The controller is the big deal on these after you get past "you are the final assembly, testing, troubleshooting, quality control and alignment" part of these and maybe you have hit the key for that. A lot of interest.Are you feeling the pressure? Maybe my controller will show up today. It's back to smashing and ruining aluminum for me this morning.

I wonder if your other thread should be merged with this one?

[Retroplayer]

You do know that torque and speed goes down as you increase microstepping, right?

Obviously, I had understood the opposite based on my research. Do you have a source for that?

Why would torque decrease with more steps? That doesn't even make sense. The closer the drive signal is to a sine wave, the more holding torque you get between steps, the smoother the motor will run. Speed, I could possibly understand, but decreased torque makes no sense at all.

[Retroplayer]

Retro I don't know if you noticed or not but this thread is at 832 views this morning! I looked back a ways but only saw "K40 expectations" really a lot higher than this one. Rolf started something here that has hit a nerve but I think the lighters are being waved for you. How does it feel to have groupies? :-)
The controller is the big deal on these after you get past "you are the final assembly, testing, troubleshooting, quality control and alignment" part of these and maybe you have hit the key for that. A lot of interest.Are you feeling the pressure? Maybe my controller will show up today. It's back to smashing and ruining aluminum for me this morning.

I wonder if your other thread should be merged with this one?

Perhaps I will just refer to it once I get to that point in my other thread.

[Retroplayer]

I don't want this to diverge into discussion about Microstepping, but here is a read that gives far more than anyone here probably wants to know:

http://users.ece.utexas.edu/~valvano...rMicrostep.pdf


Stigoe, you are correct in two cases I can think of. 1. If you are trying to compare the sticking torque to a full step drive. Yes, microstepping will have less torque than full step drivers at this point. As long as the motor doesn't move, great. But then we have a brake. Regardless, full step drivers are impractical for something like this and EXTREMELY load and imprecise.

The second case is at high speeds. There is a theoretical limit, of course. Microstepping causes harmonics and the mechanical components of the stepper will act as a low pass filter. Eventually you reach a point where the motor itself completely filters out the microstepping currents and the advantages of microstepping begins to diminish.

But none of the scenarios in which microstepping has disadvantages has any relevance here. We are well within the realm of the advantages to microstepping in this application.

Obviously full sine-wave synchronous mode drivers would be the very best, but they are also extremely expensive and arguably overkill here.

[Rolf_K]

That would be fine assuming you already have the Arduino mega2560 board and stepper drivers. You already have the stepper drivers as well?

I don't know if my Arduino is a Mega 2560, there is a bunch of numbers on the chip but they are awfully hard to read. Here's a picture maybe you can make heads and tails of it:



I think I posted a previous picture showing the stepper drivers in my 50 W generic laser/engraver.

Side note: With all the hits these blogs are having, it would seem that the manufacturers would take notice that the CO2 laser/engravers DIY's are not dead. I contacted a major manufacturer in China about a year ago to see if they where interested in manufacturing an open-source CO2 laser controller, of course nothing happened :-(

[Stigoe]

Obviously, I had understood the opposite based on my research. Do you have a source for that?

Why would torque decrease with more steps? That doesn't even make sense. The closer the drive signal is to a sine wave, the more holding torque you get between steps, the smoother the motor will run. Speed, I could possibly understand, but decreased torque makes no sense at all.

For low speed, you get higher torques with microstepping, but with higher speed (like with a laser cutter) you get higher torque without microstepping.
- One source - Look for the posts by Mariss Freimanis, the designer of Gecko Drives
- Another source

Increasing microstepping decreases speed is fairly obvious if you think about it.
You have a fixed number of pulses coming from the controller into the drive, let's say 1000/sec.
With a 1/2-step drive, this will give you 500 full steps per sec, or 2.5 revolutions per second (1.8deg motor)
With 1/10-step drive, this will give you 100 full steps per sec, or 0.5 revolutions per second

So if you double your microstepping, say go from 1/16 to 1/32, you will halve your resultant speed as the pulse frequency from the controller is constant.

[Retroplayer]

I don't know if my Arduino is a Mega 2560, there is a bunch of numbers on the chip but they are awfully hard to read. Here's a picture maybe you can make heads and tails of it:



Side note: With all the hits these blogs are having, it would seem that the manufacturers would take notice that the CO2 laser/engravers DIY's are not dead. I contacted a major manufacturer in China about a year ago to see if they where interested in manufacturing an open-source CO2 laser controller, of course nothing happened :-(

Nope, that won't work. That is an MBED controller. Very different. It runs Linux.

[Stigoe]

I don't know if my Arduino is a Mega 2560, there is a bunch of numbers on the chip but they are awfully hard to read. Here's a picture maybe you can make heads and tails of it:

That looks like an mBed board, using a completely different chip.

[Retroplayer]

For low speed, you get higher torques with microstepping, but with higher speed (like with a laser cutter) you get higher torque without microstepping.
- One source - Look for the posts by Mariss Freimanis, the designer of Gecko Drives
- Another source

Increasing microstepping decreases speed is fairly obvious if you think about it.
You have a fixed number of pulses coming from the controller into the drive, let's say 1000/sec.
With a 1/2-step drive, this will give you 500 full steps per sec, or 2.5 revolutions per second (1.8deg motor)
With 1/10-step drive, this will give you 100 full steps per sec, or 0.5 revolutions per second

So if you double your microstepping, say go from 1/16 to 1/32, you will halve your resultant speed as the pulse frequency from the controller is constant.

Why would you have a fixed number of pulses when you go from 1/16 to 1/32? Of course not. Not only your speed would be off, but so would the position. You tell it to go 10mm and it goes 5mm. You are correct, but this is also irrelevant. You adjust this with steps/mm and the firmware works out all the math. There is of course a limit to what the controller can do.

I'm not saying you are incorrect, just that I think you are looking at this from purely a motor standpoint, and we have a system here with pulleys, timing belts, mechanical friction, etc... We have movment and momentum, dampening forces, acceleration, etc... We are getting to that point where we could argue theoretical vs. real world. Those worlds always clash

As far as the speeds, unless you have a really really crappy motor with a very high coil resistance, you are not going to be moving at the speeds required to reach the point that you are talking about. But, again, you are theoretically correct. If we reached those points at which it was a problem, the laser wouldn't even have enough time to make a mark on the material.

But I will read your sources and change my statement if I am wrong. Thank you for the links!

[Retroplayer]

For low speed, you get higher torques with microstepping, but with higher speed (like with a laser cutter) you get higher torque without microstepping.
- One source - Look for the posts by Mariss Freimanis, the designer of Gecko Drives

Oh, this is one I had already read before. If you read his complete post, I think you will see that you are misunderstanding him and he is actually agreeing with much of what I said above (unless *I* am misunderstanding him, but it does match up with several other sources, too.) I touched on much of that above in regards to comparing uStepping to a full step. Again it's true as long as the motor isn't moving, but completely impractical for this purpose. That's the trouble with giving out too much information. Muddies the waters.

[Rolf_K]

Thank you, you must be correct because I remember the word mBed from my Lalos instructions.

[Retroplayer]

Thank you, you must be correct because I remember the word mBed from my Lalos instructions.

There is a really nice 3D printer board out there that uses this and gives you network connectivity as well. But I have no experience with it.

EDIT: Do you mean Lasersaur, not Lalos?

Lasersaur Store

[Rolf_K]

No, I just misspelled Laos. I am using Dragon speaking naturally for most of my post, it is great but makes mistakes that my proofreading has a hard time catching.

[Stigoe]

Why would you have a fixed number of pulses when you go from 1/16 to 1/32? Of course not. Not only your speed would be off, but so would the position. You tell it to go 10mm and it goes 5mm. You are correct, but this is also irrelevant. You adjust this with steps/mm and the firmware works out all the math. There is of course a limit to what the controller can do.

I'm not saying you are incorrect, just that I think you are looking at this from purely a motor standpoint, and we have a system here with pulleys, timing belts, mechanical friction, etc... We have movment and momentum, dampening forces, acceleration, etc... We are getting to that point where we could argue theoretical vs. real world. Those worlds always clash

As far as the speeds, unless you have a really really crappy motor with a very high coil resistance, you are not going to be moving at the speeds required to reach the point that you are talking about. But, again, you are theoretically correct. If we reached those points at which it was a problem, the laser wouldn't even have enough time to make a mark on the material.

But I will read your sources and change my statement if I am wrong. Thank you for the links!

I looked further in the posts by Mariss, and I also see that the torque with microstepping doesn't really drop off as the resolution increases. Seems like there has been a lot of misunderstanding floating around, because this is the first time I've seen this information.

But when it comes to speed, I still say that you are wrong in that increasing microstepping increases speed. Of course you would need to change the settings to compensate for the change to get the correct number of steps/mm, but that wouldn't increase the speed as such. You would have to tell the controller to increase the speed of the pulses to keep the same speed (of the motor) when you increase microstepping.