Laser pointer discussion. Read/write reviews of laser pointers and laser pointer companies. Learn about all types of laser pointers and lasers





Welcome to Laser Pointer Forums! If you are looking for a laser pointer or want to compare different laser pointer companies, you may want to check out the LPF Laser Pointer Company Database. The link will open in a new window for your convenience.








Green Laser Pointers by Category Blue Laser Pointers by Category Red Laser Pointers by Category
Yellow Laser Pointers by Category Violet Laser Pointers by Category Orange Laser Pointers by Category
Top Laser Pointers by Power - 1 Watt+ Top Laser Pointers by Power - 500mW+ Top Laser Pointers by Power - 250mW+
Laser Pointer Database High Power Laser Pointers Laser Pointer Diodes
Laser Technology Laser Pointer Parts Lasers by Wavelength
Top 10 Laser Pointer Companies Laser Pointer Company Database Visible Beam Laser Pointers


One laser store meets all your needs

























Go Back   Laser Pointer Forums - Discuss Laser Pointers > Lasers > Experiments & Modifications



LPF List of Laser Pointer Companies (link opens new window)



Reply
 
LinkBack Thread Tools Display Modes
Old 02-04-2011, 12:48 AM #1
NsN NsN is offline
Junior Member
 
Join Date: Feb 2011
Posts: 4
Rep Power: 0
NsN is just really niceNsN is just really niceNsN is just really niceNsN is just really nice
NsN NsN is offline
Junior Member
 
Join Date: Feb 2011
Posts: 4
Rep Power: 0
NsN is just really niceNsN is just really niceNsN is just really niceNsN is just really nice
Default Temporarely Reducing a 200 mW Laser to 1 mW for safety

Hi,
i hope this is the correct forum, it might also fit into the safety section.

I'm currently working on a concept for a CNC Laser rig. The main target is to expose photo positive pcb material to create circuit boards.
As a bonus i might want to brand some soft materials and maybe vaporize a layer of black coating from a copper clad board.

I'm currently planing to use this 405 nm Laser:
DealExtreme: $29.10 Focusable 200mW 405nm Burns Match + Money Detector Blue-Violet/Royal Purple Laser Pen (2*CR2)

The whole rig will of course be covered with an appropriate safety hood with an automatic off switch.

However i figure that i will need to focus the laser from time to time. For that purpose i would like to include a secondary circuit that physically limits the power output to safe levels. While i will be using protective goggles, i want to make sure that there is no way the full 200mW beam can be output with an open cover.

From what i have read so far, there are 3 ways to limit the power:
- Adding some opaque material in the beam
-- This is not usefull since it might change the focus, and the full power is still output, just absorbed early on

- Limiting the current
-- This is theoretically the best option, but I probably won't be able to limit the current to get it down to 1mW, because of the turn on threshhold

- PWM (As in switching the beam on and off)
-- This is the method i'm most used to from my current electronics experience, however this will still output the full power beam for every pulse, so i will need a frequency > 5kHz and i will need to be carefully to select a power supply that works with PWM. Also the circuit has to be very robust to make sure it doesn't get stuck in the on position.


My approach so far would be to combine the last two options. Limit the current to a bit over the threshhold and then use a 555 timer to generate a frequency of ~10kHz with a duty cycle of maybe 1% or less, depending on the current.
The whole laser could than be switched from the normal full power supply to the lower power supply to focus it.

Would this provide a somewhat safe environment to operate the laser? (The laser would still be pointed downwards, but there might be accidental reflections, i might cross the beam with my hand, it would be focused on the same area for a couple of minutes, etc...


NsN is offline   Reply With Quote







LPF List of Laser Pointer Companies (link opens new window)







Old 02-04-2011, 01:56 AM #2
Bionic-Badger's Avatar
Class 4 Laser
 
Join Date: Oct 2007
Location: Oregon, USA
Posts: 5,478
Rep Power: 3157
Bionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond repute
Bionic-Badger Bionic-Badger is offline
Class 4 Laser
Bionic-Badger's Avatar
 
Join Date: Oct 2007
Location: Oregon, USA
Posts: 5,478
Rep Power: 3157
Bionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond reputeBionic-Badger has a reputation beyond repute
Default Re: Temporarely Reducing a 200 mW Laser to 1 mW for safety

Why don't you just have a calibration area on your boards, run it at a moderate power (~30mW or something), and then perform the focusing on that section? You could also fix it so it'll focus at a certain height and use a camera on the side to determine what height the surface is at.
Bionic-Badger is offline   Reply With Quote
Old 02-04-2011, 01:41 PM #3
NsN NsN is offline
Junior Member
 
Join Date: Feb 2011
Posts: 4
Rep Power: 0
NsN is just really niceNsN is just really niceNsN is just really niceNsN is just really nice
NsN NsN is offline
Junior Member
 
Join Date: Feb 2011
Posts: 4
Rep Power: 0
NsN is just really niceNsN is just really niceNsN is just really niceNsN is just really nice
Default Re: Temporarely Reducing a 200 mW Laser to 1 mW for safety

Basically this is what i want to do, just that instead of a moderate power of ~30mW i want to do this at a minimal power of ~1mW. I doubt that i can just reduce the current so drastically, that's why i want to try to limit the current and then apply the PWM.

By the way, are there any good ways to automatically focus a laser?
I was thinking of using a light dependant resistor below a pinhole and varying the height of the pointer until i get minimum resistance. I'm just not sure if a resistor with a pinhole opening is the best way to go.
NsN is offline   Reply With Quote
Old 02-05-2011, 03:05 PM #4
Benm's Avatar
Class 4 Laser
 
Join Date: Aug 2007
Location: Netherlands
Posts: 7,442
Rep Power: 19481
Benm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond repute
Benm Benm is online now
Class 4 Laser
Benm's Avatar
 
Join Date: Aug 2007
Location: Netherlands
Posts: 7,442
Rep Power: 19481
Benm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond repute
Default Re: Temporarely Reducing a 200 mW Laser to 1 mW for safety

Quote:
Originally Posted by NsN View Post
Hi,
- PWM (As in switching the beam on and off)
-- This is the method i'm most used to from my current electronics experience, however this will still output the full power beam for every pulse, so i will need a frequency > 5kHz and i will need to be carefully to select a power supply that works with PWM. Also the circuit has to be very robust to make sure it doesn't get stuck in the on position.


My approach so far would be to combine the last two options. Limit the current to a bit over the threshhold and then use a 555 timer to generate a frequency of ~10kHz with a duty cycle of maybe 1% or less, depending on the current.
The whole laser could than be switched from the normal full power supply to the lower power supply to focus it.
I have used PWM on current sources, mainly to do some research into average vs peak current performance of laser diodes. Its not hard to pull off at all, as long as you use a proper driver (opamp based, or even the 2-transistor circuit).

Modulating at around 10 kHz should be fine, if you go much higher capacitances in the laser diode and its wiring may start to interfere with the current source. You can reduce the output power to whatever you like using this method, and go to full power by adjusting the duty cycle. A nice thing about PWM is that you can get a linear control using a potmeter, so you can set the exact average power you want.
Benm is online now   Reply With Quote
Reply

Tags
power, pwm, safety





Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On











Loading








Green Laser Pointers by Category Blue Laser Pointers by Category Red Laser Pointers by Category
Yellow Laser Pointers by Category Violet Laser Pointers by Category Orange Laser Pointers by Category
Top Laser Pointers by Power - 1 Watt+ Top Laser Pointers by Power - 500mW+ Top Laser Pointers by Power - 250mW+
Laser Pointer Database High Power Laser Pointers Laser Pointer Diodes






Privacy Policy | Advertising Disclaimer | Terms of Use


 


All times are GMT. The time now is 09:01 AM.


Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO
Privacy Policy | Advertising Disclaimer | Terms of Use
Copyright (C) 2017 Laser Pointer Forums, LLC