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Fórum » Only in English » Technologies » Diode Lasers. (Using Diode Lasers with CNC Machines.)
Diode Lasers.
csewe Dátum/Date: Szombat, 2013-02-09, 14:21 | Üzenet/Post # 421
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I understand the concept here.
Works nicely.
But those who are not familiar with electronics, it is difficult to implement.
I am experienced in electronics and programming, so I started to build the circuit using PIC.

We have our own conception a pure software solution to the problem.
The feed rate Changes made basis.
But for I need to write a program.
When I finished my laser, I will try it.


Az üzenetet módosította/Modified by csewe - Szombat, 2013-02-09, 15:20
 
Dave Dátum/Date: Szombat, 2013-02-09, 15:39 | Üzenet/Post # 422
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Welcome Csewe!
I use a circuit with counters and a digital to analog coverter to modulate my diode laser. It uses the step and direction parallel port lines as input. I don't think I've posted the circuit here, so I'll do that now.

Dave

Hozzáadva (2013-02-09, 15:39)
---------------------------------------------
This circuit doesn't drive the laser directly, but instead just outputs 0-5 volts that the laser modulation circuit needs as input.
Dave

Csatolások/Attachments: 2042762.png(55Kb)
 
csewe Dátum/Date: Szombat, 2013-02-09, 15:56 | Üzenet/Post # 423
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Dave,

Mine ask for laser with TTL signal.
I have a similar idea.
If the Z-axis step is denser or less frequent, it is equally a type of PWM.
You just have to broaden your step pulses 74hc121 an integrated circuit.


Az üzenetet módosította/Modified by csewe - Szombat, 2013-02-09, 16:35
 
Dave Dátum/Date: Szombat, 2013-02-09, 19:17 | Üzenet/Post # 424
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For a while I was using my laser to do black and white images, with just the direction line from mach3 to control the laser. That had some problems because the direction line is active just before the first step pulse arrives.

Right now, my laser driver is a flexmod p3. It will accept a ttl level signal for black and white, or an analog voltage from 0 to 5 volts from the counter circuit. For ttl mode engraving, I'm using John's PicEngrave program and a mach3 profile set up so that it runs the counter circuit in reverse - one step downward gives me the full 5 volt output.

For shaded images, my mach3 profile runs the counter forwards for axis moves downward and reverse for upward axis moves to get a variable output voltage.

Other folks here use an analog encoder coupled to their z axis to produce a variable voltage. It works very well too.
Dave
 
KisKZ Dátum/Date: Szombat, 2013-02-09, 19:30 | Üzenet/Post # 425
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Idézet (Dave)
That had some problems because the direction line is active just before the first step pulse arrives.

Hello Dave!

First sorry if I misunderstand your problem!

How you are use your laser diode?
You always turn on and off fully?

Just because I'm on my board never turn off fully power. Only when have not supply on it.
On 1W diode, when I have not enable I'm only reduce current to lowest as possible (200mA). With this current diode do not have enought power for burning but the red light is on for find position on part. It better for lifetime of diode too. I got information, switching on-off is not so good for this.

With this method I can use Z DIR to switch on or off diode and same time I have all time red light for positioning.

Can somebody explain me this counter circuit? How it is work?
How diode power is controlled? With Analog power or with ttl?
Zolibá, on Hungarian laser technologie forum made an PWM mode laser driver, but at first test this kill a laser diode.
We do not know nothing about PWM power supply possibilities of laser diodes. sad

Thank you!

Peter
 
JJWMACHINECO Dátum/Date: Szombat, 2013-02-09, 19:31 | Üzenet/Post # 426
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Idézet (Dave)
Other folks here use an analog encoder coupled to their z axis to produce a variable voltage. It works very well too.


Other folks??? CSEWE, Dave's talking about me. I'm the only one at this time that uses a shaft encoder that I'm aware of and I'm getting excellent results with this very simple setup. The shaft encoder is tied to a Flexmod P3 also.

Jeff


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
Dave Dátum/Date: Szombat, 2013-02-09, 20:57 | Üzenet/Post # 427
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Hi Jeff, yes, your results ARE better than excellent!!!!! smile

Peter,
When I used the direction line by itself to control the laser, I was getting blurry images. That's because the direction line has to be stable before the step pulses occur. What that means is that when the X-axis moves, the burn starts before the X axis sees the first X step pulse. So as it moves left to right, the burn starts in a slightly different spot than when it's moving right to left. The difference in positions is quite small, but it is enough to get a blurry image.

The laser driver I have is a flexmod p3. It's capable of supplying up to 4 amps to the laser diode, and also has a bias setting so that there is always some current to the laser diode when power is applied. Its input can be either a variable voltage from zero to five volts, or a ttl level pulse of 5 volts. At zero volts, the laser diode is on at 0% output, 2.5 volts gives 50% outout, and 5 volts gives 100% output.

http://hacylon.case.edu/ebay/laser_diode/FlexModP3.php

The laser diode output is bright blue, 445 nanometers. I don't have any other information for it though.

The binary counter circuit I built uses the step and direction parallel port lines to produce a variable voltage that is related to the 'depth of cut'. The direction line controls whether the counters count up or down, and it counts the number of step pulses. The two counter chips are capable of counting from 0 to 255. I have a C axis defined in mach3 on parallel port pins 14 and 16, and it drives the counter circuit instead of driving a stepper motor driver. The counters feed an R-2R resistor network that translates the counter's value into a voltage. This is used to feed the TLV272 "rail-to-rail" op amp that outputs the 0 to 5 volts signal to the flexmod p3 board. Normal op amps like the LM358 don't give the full 5 volt swing.

For shaded images, in the mach3 profile I have the steps per inch defined so that each C-axis step is 0.0001 inches and the direction line active level is defined so that the counters count up as the C-axis value becomes more negative (C-0.0255 is the "depth" for a full count and the full 5 volt output). The counters count down as the C-axis value becomes more positive (C0.0000 gives zero volts output from the counter circuit). The counter board has a reset switch so that I can set the count to zero at the g-code "depth" where the lightest burn occurs on the wood I'm using. There's also a potentiometer that's used to set the maximum voltage when the full 5 volts burns the wood too dark.

The mach3 profile for black and white images has the direction line reversed, so that one step downward (from C0.0000 to C-0.0001) runs the counter backwards one step. This gives a full count of 255 for that one step, which results in a full 5 volt output from the counter circuit board.

Dave
 
KisKZ Dátum/Date: Szombat, 2013-02-09, 22:35 | Üzenet/Post # 428
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Idézet (Dave)
That's because the direction line has to be stable before the step pulses occur. What that means is that when the X-axis moves, the burn starts before the X axis sees the first X step pulse. So as it moves left to right, the burn starts in a slightly different spot than when it's moving right to left. The difference in positions is quite small, but it is enough to get a blurry image.


Hello Dave!
Now I understand! Thank you!
 
JJWMACHINECO Dátum/Date: Szombat, 2013-02-09, 23:06 | Üzenet/Post # 429
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Idézet (csewe)
Mine ask for laser with TTL signal.
I have a similar idea.
If the Z-axis step is denser or less frequent, it is equally a type of PWM.
You just have to broaden your step pulses 74hc121 an integrated circuit.


Would this not still be like pulsing the laser and not really varying the power to get shades if your using a TTL laser driver? "Pulse" Width Modulation. With the methods me, Dave and John are using, there are no pulses to varying voltage to the laser driver which in turn has no pulses to varying amperage to the LD. There are no dots in the lasered image like a dithered B&W TTL engraving. My shaft encoder is powered by the USB port on my PC and outputs 0-5 linear analog voltage based on the rotation of the shaft which makes the analog modulated laser output linear.

Jeff



Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
csewe Dátum/Date: Vasárnap, 2013-02-10, 05:20 | Üzenet/Post # 430
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JJWMACHINECO,

This rotation encoder is a good idea.
But for me the analog signal is not correct.
 
JJWMACHINECO Dátum/Date: Vasárnap, 2013-02-10, 14:55 | Üzenet/Post # 431
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They do have them with 10 and 12 bit PWM
http://www.usdigital.com/products/encoders/absolute/rotary/shaft/MA3


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
csewe Dátum/Date: Vasárnap, 2013-02-10, 15:45 | Üzenet/Post # 432
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This is good.
Able of the pwm.
Here in Hungary, it is MAB22AH of the tupus.
 
Dave Dátum/Date: Vasárnap, 2013-02-10, 16:47 | Üzenet/Post # 433
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Csewe,
I also have the ball bearing analog version of this encoder but I wanted to keep the z axis available for depth control so that I might be able to engrave on a surface that's not flat.
If you decide to try this encoder, keep in mind that the cable and connector is sold separately. The connector on my analog encoder is so small it would be difficult for me to attach wires to it. You might want to also get a connector with a few feet of cable attached.
Dave
 
csewe Dátum/Date: Vasárnap, 2013-02-10, 16:57 | Üzenet/Post # 434
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Dave,

Thank you for the information.
 
JJWMACHINECO Dátum/Date: Hétfő, 2013-02-11, 15:04 | Üzenet/Post # 435
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My Laser diode is my brush and PicEngrave Pro 4 is my paint. Tried some white artist canvas using TTL and the texture sure gave it a real nice effect. Sprayed some clear protective finish on it also.

Csatolások/Attachments: 8377399.jpg(200Kb)


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
Dave Dátum/Date: Hétfő, 2013-02-11, 15:47 | Üzenet/Post # 436
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Jeff, that came out really nice! Solves uneven burning because of the wood's grain!
I guess I'll have to add this medium to my shopping list along with some mirrors. We're getting some freezing rain on top of the foot of snow on the ground, so I'm not going to get to go shopping today I guess.
I wonder how canvas would do with a shaded image instead of ttl mode? I think you mentioned that you adjusted the gamma for this pix. What was the setting you used?
Dave
 
JJWMACHINECO Dátum/Date: Hétfő, 2013-02-11, 16:17 | Üzenet/Post # 437
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Thanks Dave.

I found out that the canvas burns hard like the mirrors do so I will have to start at a lower Z depth. I will try greyscale in the next day or two. This one I adjusted gamma to .8 and sharpened to 10. Used Atkinson @.125 when dithering. Ran it 50IPM and used Output Laser G-code.

It also puts out fumes that you have to be careful with and where it burns will wipe off easy if you don't seal it with something.

Jeff


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
Dave Dátum/Date: Hétfő, 2013-02-11, 16:24 | Üzenet/Post # 438
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Thanks Jeff! I always have trouble with fudging the image to make it burn right. Maybe it would burn easier if it was tinted with some dye or something first. I'd rather use grayscale mode than ttl because it's faster.
Dave
 
csewe Dátum/Date: Hétfő, 2013-02-11, 18:07 | Üzenet/Post # 439
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JJWMACHINECO,

Beautiful work.
Must a long times before I do that I make.
 
JJWMACHINECO Dátum/Date: Hétfő, 2013-02-11, 23:11 | Üzenet/Post # 440
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Thanks CSEWE.

Can't wait to see your laser engravings.

Jeff


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
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