Re: Laser Pen that writes into plastic! [video]
uzzors2k, Sun Jun 17 2007, 12:53PM

Nice. What is the output power? Did you collimate the beam, and if so how did you do it? I have a junked CD-RW burner which should contain an IR laser diode, not as much power as a DVD laser but still enough to be fun. I think I might try using the lens form a standard laser pen for collimating.

Re: Laser Pen that writes into plastic! [video]
Madgyver, Sun Jun 17 2007, 08:51PM

Output Power schould be around 100-120mW. The Beam is only crudely collimate with the focus lens of that unit. (The Lens which sits on voice coils)

The laser diode is mounted into a metal tube and the lens can be adjusted by turning a screw.



This is the lens.

Re: Laser Pen that writes into plastic! [video]
j.azz, Tue Jul 17 2007, 07:54PM

That's nice.
I just bought a new DVD burner to have a reason to disassemble the old one ;)
What do you use as power supply? Currently I'm using a 3,7V mobile phone accu with a 8,3 ohm resistor, giving about 400mA.

To Uzzors:

Nice. What is the output power? Did you collimate the beam, and if so how did you do it? I have a junked CD-RW burner which should contain an IR laser diode, not as much power as a DVD laser but still enough to be fun. I think I might try using the lens form a standard laser pen for collimating.

The infrared lasers are also fun. If well collimated they can burn black plastic too.

Re: Laser Pen that writes into plastic! [video]
c4r0, Fri Jul 20 2007, 11:37AM

I've built a simple regulated current source for my DVD-RW laser diode. Its very useful :)




BTW check out my DVD laser ploter : :)

Re: Laser Pen that writes into plastic! [video]
Dalus, Fri Jul 20 2007, 02:01PM

Nicely done, looks quite overpowered, do you have a way to measure the optical power?

Re: Laser Pen that writes into plastic! [video]
c4r0, Sat Jul 21 2007, 09:23AM

Actually no. But I can measure a characteristic of the laser diode using a photodiode. It gives me a shape of characteristic without scale on the optical power axis (or with photodiode current on this axis):

Re: Laser Pen that writes into plastic! [video]
j.azz, Sun Jul 22 2007, 08:33PM

hmm, I don't know what I did wrong but I just killed two of my IR-LDs with measured 10mA... Aren't 12V bad for these LDs?! Or have I a momentarily lack of intelligence at the moment... :(

Re: Laser Pen that writes into plastic! [video]
Madgyver, Sun Jul 22 2007, 08:58PM

Killing the diode with 10mA sounds odd. The 12V from the schematic, are not directly connected to the diode of course. The circuit automaticly regulates it, to achieve constant current.

Maybe you reversely connected the diode?

Re: Laser Pen that writes into plastic! [video]
j.azz, Mon Jul 23 2007, 04:53PM

arggg.... after several testings with normal LEDs, which where successfull, I finally killed my 650nm LD... I really don't know haow it happened, not connected in reverse, measured current below 30mA, just turned into a useless and poor red LED!

Re: Laser Pen that writes into plastic! [video]
Madgyver, Mon Jul 23 2007, 05:02PM

Sounds realy odd. What are you using as the power source? A Battery or a power supply unit?

Re: Laser Pen that writes into plastic! [video]
j.azz, Mon Jul 23 2007, 05:28PM

A 12V sealed led gel battery.
I guess I've found a possible reason:
(Own stupidity)
I had the switch after the whole circuit, then the LD.
May the idle voltage charge of 12v in the capacitor been enough to kill the diodes?

Re: Laser Pen that writes into plastic! [video]
c4r0, Mon Jul 23 2007, 05:41PM

Yes, this is the reason. It's killing the LD's this way even without the cap. I've killed a few my diodes this way too before i found out what's going on :P The capaciror should be soldered directly to the LD pins. If you want a switch, you should add it between R5 and D2, or even before all circuit on the 12V line.

Re: Laser Pen that writes into plastic! [video]
Madgyver, Mon Jul 23 2007, 06:05PM

Oh, thats too bad. Poor little diode.

@C4r0 Your laser plotter diode uses 250mA of current right? What drive was it from (what was its speed)? I never use more then 150mA cause I'm a chicken and don't want to ruin it.

Re: Laser Pen that writes into plastic! [video]
j.azz, Tue Jul 24 2007, 02:09PM

@Madgyver:
Mine was from a 8x speed NEC DVD burner and it could handle 400mA @ 3,7V from a mobile phone accu with a resistor in series of about 8 to 10 Ohms before I tested another power supply. Because I only had my fingers as heatsink I couldn't let it run for longer than about 10 to 15 seconds.

@c4r0:
Thx for the hint. Guess I'll get a new DVD burner and'll do better... ;)

Re: Laser Pen that writes into plastic! [video]
Madgyver, Tue Jul 24 2007, 02:33PM

Try this constant current source, quite simple and reliable:

,101,0,0,1,0

The text is in german, but I don't think you will need more then the schematic and the formula.

Re: Laser Pen that writes into plastic! [video]
j.azz, Tue Jul 24 2007, 03:08PM

Thanks. Looks quite interesting but I don't think I'll have problems with the german language -> location^^

Re: Laser Pen that writes into plastic! [video]
Madgyver, Tue Jul 24 2007, 04:41PM

Oh yeah, i haven't noticed ^^

Re: Laser Pen that writes into plastic! [video]
c4r0, Fri Jul 27 2007, 09:49AM

250mA is a max current, actually i use rather 200mA.

If i understand the question properly, it was drove from LPT port with simple transistor buffer (it uses unipolar, four coil, stepper motors). But the speed of plotting is limied by the mechanical part. It moves with max speed about 0.5mm/s.

You just have to ruin one diode to check it :P It's good to get a few same model DVD burners.

Re: Laser Pen that writes into plastic! [video]
Madgyver, Sat Jul 28 2007, 11:20AM


Ah sorry, no. I meant the speed from the DVD drive. Was it a 16x Drive or something like that?

Re: Laser Pen that writes into plastic! [video]
c4r0, Sat Jul 28 2007, 09:49PM

Oh, it's from 8x drive :P LG GSA-4082.