Power Requirements for a Laser Module

[QuackMasterDan]

Hello there, I have been obtaining my 5mW Green laser modules by extracting them from laser pointers. I then create my own voltage regulator using a LM317T which I can set to whatever voltages I need. As these lasers are powered by two AA batteries, making for a combined voltage of 3.0v. I then solder the positive and negative wires coming from my voltage regulator to the module, and it lights up.

For two separate projects I've created two different regulators, one ran @ 3.08v, and the other @ 3.01v. The 3.01v regulator has never had any problems and seems to be able to run indefinitely. I am measuring their voltage with a multimeter.

In creating my spirograph (Which turned out great, until I killed all three laser modules) I connected the modules to the 3.08v supply. And after about 20 minutes of sporadic use with each module all three refuse to turn on even with AA batteries.


1) Could an extra .08v kill my laser modules?
2) How can I prevent this from happening again (I've heard something about lasers being current limited instead of voltage limited, temperature dependent, how can I control the current)?
3) And finally, will powering the laser diodes at something much lower (~2.90v) cause any extra wear and tear on the laser while still turning it on?

Any information would be greatly appreciated.

 

[wesdaman14]

yes 0.8 volts will do damage. it really depends on how long you run the laser at. since these are pen modules, then need some good heat sinking at that power of 3.08 volts. normally 2X 1.5v aaa will give around 2.96 volts when the laser is in use. when you run it at that current level the drive somehow gets used to the voltage. But when you add more voltage the driver cant handle it and send all the extra current straight to the diode as it has no where else to go. all 3 of your modules the 808nm IR diode died. Do not look into the laser to see if it works, it may blind you.

 

[billg519]

Laser diodes such as the 808nm pump diode in a green module require a current regulator as the power supply. This can be made with an LM317, look up the DDL or daedal driver on this site. You must have a rough idea of how much current the IR pump diode can take. (1.25/desired current = resistor required for LM317)

A voltage regulator will attempt to maintain the set voltage to the load. The voltage regulator will put in as much current as it can in an effort to keep the voltage at the set level. This will kill a current sensitive device like a laser diode. You need a current regulator, it will keep the current to the diode constant, preventing an overload. (as the diode warms up, its resistance changes, current regulator essentially varies the voltage to keep the current constant)

 

[QuackMasterDan]

I guess I am using the wrong name for what I created, as it is the exact design you're talking about with a DDL driver. This is my own guide for how I create my regulator/DDL.

Thanks for the quick response, I guess the voltage was just too high @ 3.08v. Will it add extra stress on the laser to run it @ a lower voltage of 2.90v?

 

[wesdaman14]

[highlight]Will it add extra stress on the laser to run it @ a lower voltage of 2.90v?[/highlight]

No, Certainly not. it will actually last longer, but it wont be as bright as 3v. if you have the Flex drive, they actually run full power until the batteries die all the way.

 

[billg519]

Your circuit still appears to be a voltage regulator. Look more closely at the ddl schematic on this site. Once you finally have a current regulator set to the appropriate drive current for your IR pump diodes, you won't have to worry about 3.01 or 3.08 volts. Laser diodes are driven with current, the battery simply has to provide the diodes voltage rating from the specs plus overhead for the regulator. To drive an IR pump diode with an LM317, well many small IR diodes use about 1.8 to 2.2 volts, LM317 likes a good 3v overhead, so you'd want about 6v or more of battery, a pair of 14400 (AA size, from DX) lithiums would run this.

 

[GooeyGus]

As bill said, you need to build a current regulator. Current kills these things.

With a constant current driver, the module will only use the voltage it requires to operate at the set current level. So all you need to do is set the current and the voltage will take care of itself.

 

[QuackMasterDan]

Well I've got a <5mw Green laser-pointer module and don't know how to determine what current in mA it would use.

It's one of these cheap laser pointers http://www.bestofferbuy.com/5mw-powerful-green-laser-pointer-pen-p-110.html.

I would guess 250mA as I've seen that reading for other 5mW Green lasers, what amount of current do you believe I would need for this?

 

[ElektroFreak]

Well I've got a <5mw Green laser-pointer module and don't know how to determine what current in mA it would use.

It's one of these cheap laser pointers http://www.bestofferbuy.com/5mw-powerful-green-laser-pointer-pen-p-110.html.

I would guess [highlight]250mA[/highlight] as I've seen that reading for other 5mW Green lasers, what amount of current do you believe I would need for this?

That would be the right current for pretty much any 5mW pointer

 

[QuackMasterDan]

I'm not using a lone green laser diode, its the entire module from the laser pointer with the driver board already attached.

So from what I've read, a DDL driver controls current to the laser, and the voltage itself is not important as long as the proper amount of current (250mA for this <5mw Green laser) is supplied. Since I've got a module, I will solder  a capacitor to the positive and negative terminals on my module, as if it ever gets disconnected and reattached it will fry the laser?

This diagram seems like an excellent explanation

So I will need to purchase:
1) 47uF 16v Capacitor to provide smooth current to module and prevent spikes
2) 1N4001 diode to prevent reverse surges
3) 2x10 Ohm resistors (Is 10 ohms the proper number for a green 5mw? I don't know what resistors I'll be needing for 250mA)
4) 100 Ohm multi-turn variable resistor, so I can tune the resistance from low to high (checking it with a multi-meter to around a max of 250mA) until the laser is lit up stable
5) A LM317 to regulate the current

Hopefully I got all of that right. I also would like for this laser to be on 24/7 as it will be a display piece for the ceiling in my house, I've heard about drilling a hole in some pennies, and soldering the pennies to the outside of the laser module. Will the large amount of heat required to make a good connection between the penny and module casing fry the laser diode?


Thanks for being so understanding and patient in helping a newbie better understand how to work with lasers, I greatly appreciate it.

 

[ElektroFreak]

I'm not using a lone green laser diode, its the entire module from the laser pointer with the driver board already attached.

So from what I've read, a DDL driver controls current to the laser, and the voltage itself is not important as long as the proper amount of current (250mA for this <5mw Green laser) is supplied. Since I've got a module, I will solder  a capacitor to the positive and negative terminals on my module, as if it ever gets disconnected and reattached it will fry the laser?

This diagram seems like an excellent explanation

So I will need to purchase:
1) 47uF 16v Capacitor to provide smooth current to module and prevent spikes
2) 1N4001 diode to prevent reverse surges
3) 2x10 Ohm resistors (Is 10 ohms the proper number for a green 5mw? I don't know what resistors I'll be needing for 250mA)
4) 100 Ohm multi-turn variable resistor, so I can tune the resistance from low to high (checking it with a multi-meter to around a max of 250mA) until the laser is lit up stable
5) A LM317 to regulate the current

Hopefully I got all of that right. I also would like for this laser to be on 24/7 as it will be a display piece for the ceiling in my house, [highlight]I've heard about drilling a hole in some pennies, and soldering the pennies to the outside of the laser module[/highlight]. Will the large amount of heat required to make a good connection between the penny and module casing fry the laser diode?


Thanks for being so understanding and patient in helping a newbie better understand how to work with lasers, I greatly appreciate it.

Instead of using pennies, you can get a great heatsink for Aixiz modules or laser pointer modules from this site:

http://www.z-bolt.com/MODIIIbg-green-laser-module.html
(look at the item listed under the three green modules)

It's very inexpensive, and it provides enough cooling for even the most powerrful 5.6mm diodes. This will allow you to leave it on continuously.

EDIT: These heatsinks aren't any good for pointers, but rock for labbies. For pointers you want a Jayrob heatsink or something similar..

 

[QuackMasterDan]

I am at a loss for words now. I have waited two weeks for some more 5mW Green laser modules, and they have finally arrived. I went to my local electronics store and purchased all of the parts required for a Daedel or DDL Driver, and built a full functional adjustable current limiter.

My source supply is a 12v 1000mA wall wart and I am trying to power my laser via plug instead of batteries. As I have understood, voltage does not matter with a DDL driver as lasers are current driven devices - keep the current safe and the laser will take care of itself. The current limiter worked perfectly, I could adjust my 100 omh potentiometer and viewing the laser with my cell phone camera, could see faint infrared (purple light), as I slowly adjusted it it became brighter until green emitted from the laser, just like a battery powered laser pointer.

Everything was working perfectly, and I specifically decided to make it less dim than a regular pen would be so as to lengthen the life. That is, until smoke began pouring out of the circuitry on the board attached to the module. The burning is making me think the voltage is excessive (12v from the wall wart). Now it will no longer will emit green light, when I plug it in at the same setting green emission occurred I get infrared light and continuous smoke. Now circuits on the board are turning brown and though it can still emit infrared, the laser is toast.


The first time I regulated only the voltage, and three laser pointers died. This time I regulated only the current, and I've killed one. Do both current AND voltage need to be regulated together?

What have I done wrong?

 

[ElektroFreak]

You should not need a driver at all with green modules. The small circuit board that is attached to them is a driver, and it is more than sufficient for your module. All you have to do is apply 2-3V DC to it and it should lase.. You are overpowering the module's built in driver by attaching it to an LM317 driver... I recommend powering your green modules directly from 2 AA batteries. No other driver is necessary..

 

[QuackMasterDan]

So voltage is the primary factor? The driver board attached to the laser will regulate the current, and I just need to provide 2-3 volts.

I do not want to power this laser via batteries, it is going to be plugged into the wall. It is part of a home-made spirograph, and the fans/mirrors and laser are all powered by the same 12v wall wart power supply.

So quite simply, I just need to regulate voltage in between 2 and 3 volts, and the driver board will take care of current?

 

[ElektroFreak]

Exactly. That's what it's there for. If you use a power supply of some sort to go from the wall to the driver, make sure you check it's output with a meter before you hook up the module. Make sure the voltage doesn't exceed 3V by much if at all.. I definitely wouldn't lose much sleep over your dead modules, though. Everyone on here has burned up their fair share of stuff, that's for sure..

 

[QuackMasterDan]

Having changed my voltage regulator to 2.92 volts my spirograph is fully functional. I've been using it over the past two hours and the laser has not burnt out, and the rig seems to be relatively stable. However there is an oddity that is going on with brightness. After being left on for around 5 minutes, the brightness of the laser drops sharply. If I power it off and quickly on again, it will return to full brightness for about 1-2 seconds.

If I had to guess, my LM317 is near its heat-limit and is dropping the voltage to compensate, however I have a very large heatsink applied with thermal grease attached to it. To the touch the heatsink doesn't burn my finger, but is still very warm. The laser module itself is noticeably warm.

What could be causing the shift in brightness after 5+ minutes of use?