How to drive laser with PWM ?

General discussion of laser machines

How to drive laser with PWM ?

Postby bluewave65 » Tue Jan 10, 2012 10:00 pm

Hi,

i can`t find any resonable pwm driving solution for buildlog laser.
Only some half-way ideas ....

What do you suggest ?

M10/M11
E1P1 / E1P0
M3 / M5

I need controll beam power not only on/off system.
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Re: How to drive laser with PWM ?

Postby wklaser » Mon Jul 16, 2012 4:07 am

PWM is for RF laser tube spec
and if for glass tube,this is useless
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Re: How to drive laser with PWM ?

Postby twehr » Mon Jul 16, 2012 12:13 pm

wklaser wrote:PWM is for RF laser tube spec
and if for glass tube,this is useless


I am not sure where you got this information, but I believe you may be confusing PWM with the laser's trigger frequency. RFs use specific frequencies, but glass tubes do not.

PWM (input) is the method that ALL current laser PS use to set the power level of the output. It ranges in % from 0 to 100. It is a 5v (usually 3.3v acceptable) DC signal that is modulated by turning it on and off so that it is on a certain % of the time. The PW then, receiving such signal, drives the laser tube to the corresponding % of power. (Not linear as most PS and tube combinations vary, but close enough for this discussion.) Nearly all modern controllers use PWM to control the power, regardless of whether using RF or Glass tubes.

If you are using a modern controller (DSP, etc), then the PWM signal is provided automatically. If you are building your own controller, then you can use an analog to pwm circuit (Hobard Designs in Australia is one that comes to mind).

All modern laser PS also accept an analog (0-5v) signal.

Tell us what the original poster really wants to do and how this question came up and we will be happy to help them figure it out.

Here is an article I posted about PWM and laser output. It does not deal with the electronics part but give you a base for understanding what it does and how your laser reacts to it.
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Re: How to drive laser with PWM ?

Postby twehr » Mon Jul 16, 2012 12:16 pm

bluewave65 wrote:Hi,

i can`t find any resonable pwm driving solution for buildlog laser.
Only some half-way ideas ....

What do you suggest ?

M10/M11
E1P1 / E1P0
M3 / M5

I need controll beam power not only on/off system.


The GCode you are showing is not for PWM, but for triggering the laser on and off. PWM sets the power level. See my explanation in response to the other post. Some of those with more GCode experience may be able to help you better with setting the PWM level from code.
tim
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DIYLaser Blog
SemiHomemadeTools.com
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Re: How to drive laser with PWM ?

Postby autocrib » Fri Oct 05, 2012 9:05 pm

I have some problem, I need to boost a PWM signal at 5KHz and 450mV to 5V at 5KHz and 100mA
max. Could someone help me by providing list of the components that I need and a schematic to do this.
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Re: How to drive laser with PWM ?

Postby bdring » Sat Oct 06, 2012 2:55 pm

There are probably a lot of ways to raise the voltage, but such a high output current of 100mA rules a lot of the simple ones out. Are you sure you need 100mA? That is almost enough to drive a relay.

Fortunately, 5KHz is is pretty slow. I would probably use a simple transistor with the right saturation voltage.
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Re: How to drive laser with PWM ?

Postby 3dtech » Fri Jun 02, 2017 5:39 am

ou need to adjust your thinking; you cannot control both at the same time. The laser (and many other electrical devices) will show a voltage across itself as a function of the current passing through it. You could also say the current is a function of the applied voltage, but that's a poor way to actually control the laser as Sarge has noted.

A resistor does a decent job of limiting current. A constant-current regulator does a better - more precise - job. 3d printing mumbai pune - fdm technology
Sarge may correct me but I believe you could replace the comparator in his circuit with a single NPN transistor if you have enough signal to drive its base. The comparator gives you more flexibility.
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Re: How to drive laser with PWM ?

Postby JenniferT » Thu Jan 31, 2019 12:13 pm

What connections are you using?
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