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.
bluewave65
 
Posts: 19
Joined: Thu Jun 09, 2011 5:21 pm
Location: Czech Republic

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
wklaser
 
Posts: 24
Joined: Sat Dec 26, 2009 3:18 am

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.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

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
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

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.
autocrib
 
Posts: 12
Joined: Tue Sep 18, 2012 9:16 am

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.
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

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.
3dtech
 
Posts: 11
Joined: Tue Sep 08, 2015 6:21 am
Location: MONA TILES COMPOUND, NR. CHHANI CIRCLE, CHHANI ROAD, VADODARA - 390002. GUJARAT, INDIA.


Return to General

Who is online

Users browsing this forum: No registered users and 2 guests

cron