Complete laser noob... Please help!!!

[DTR]

If you are getting 874mW then you are giving the diode quite a bit more than 230mA. The 445 has a voltage drop around 4.5V around 1.5A.

Yes a properly set up LM317 will work fine. See the driver section for LM317 based drivers.:beer:

 

[jsteg1981]

Perhaps I am measuring it incorrectly. I am measuring the voltage and the pigtails on the diode. In other words, once everything is connected and turned on, I put my multimeter at the diode. One probe on the end of the - and other on the end of the +.

To test the current, breaking the circuit at the - end from the diode to PWS.

 

[mainefungi]

I think jsteg1981 is a little confused. The watt rating that you can calculate for electricity (P=VI) is not the same as the ratings you see listed for LASER builds.

The power rating you see on lasers is a rating of the optical power of the laser's beam, or the amount of light energy produced by the laser.

 

[jsteg1981]

I see! Then I suppose I am lucky I have yet to burn this diode out.

Now I feel lost and not sure how I should figure my calculations. Is there a formula to use to figure out the optical power based on the watt rating for electricity?

 

[mainefungi]

I see! Then I suppose I am lucky I have yet to burn this diode out.

Now I feel lost and not sure how I should figure my calculations. Is there a formula to use to figure out the optical power based on the watt rating for electricity?

Well, each diode is different. Meaning a red, blue, or violet diode will all be different, and different brands of diodes withing the same color will also be different. You need a Laser Power Meter to know for sure, which I have yet to purchase. Not in my budget if I want to stay married.

Fortunately the M-140 is common, and someone has already graphed the power ratings in reference to current. This is only an estimate, but it will get you close. Here is the graph posted by sopark4000 in another thread. Current across the X axis, and power on the right. So you see, at 230mA you are only putting out about 70mW, which is why your burn is slow.

 

[mainefungi]

This is the graph using the Three Element Glass lens, which is the one you said you purchased. There is a separate graph for the G-2 Lens.

 

[jsteg1981]

Maybe a better question would be:

How do I know when I am getting close to the LD's limit without a way to measure the optical power? I hear 1.8A is the most I should push with this LD.

 

[Th3dArKn3o]

Electrical Power and Optical Power is a big difference
on these diodes you may need around
5 times more electrical input power than optical output power !
At your setup with 3,8V and 230mA your diode will output somewhat like ~150mW depending on your lens and efficiency of the diode
so there is no formula to calculate exact output !!!

I suggest you for the full Power of the M140 Diode around 4,6-4,8V and 1,7A-1,8A the diode will then output around 2000mW (with G2 Lens) optical Power !

 

[jsteg1981]

Oh wow!!! I needed that graph! Thank you sooooo much!

 

[mainefungi]

Maybe a better question would be:

How do I know when I am getting close to the LD's limit without a way to measure the optical power? I hear 1.8A is the most I should push with this LD.

That is a pretty safe current, but I like 1.5A better. Why push the diode any harder then you have too? You will get the most life from it if you stay away from that upper limit, and make sure you keep it cool. Proper heat sinking is a must at that level. For the diode, and at that level you will want a better driver for sure.

 

[Th3dArKn3o]

That is a pretty safe current, but I like 1.5A better. Why push the diode any harder then you have too? You will get the most life from it if you stay away from that upper limit, and make sure you keep it cool. Proper heat sinking is a must at that level. For the diode, and at that level you will want a better driver for sure.

That's exactly what I said earlier forget the LM317 !
It is not adequate for an High Power Build !
Use an L200 setup costs a few bucks or an buck or boost driver !

Edit:
Depending on your heatsink and duty cycle 2A can be a safe current too
But you're right for a beginner 1,5A is much better !

 

[mainefungi]

Depending on your heatsink and duty cycle 2A can be a safe current too
But you're right for a beginner 1,5A is much better !

Considering the size of some hosts, there may not be enough room in the head for the heat sinking required at 2A.

Unless you want a 30/90 duty cycle. :tinfoil:

Of course, you could implement TEC cooling and/or a mini fan.

 

[Th3dArKn3o]

Considering the size of some hosts, there may not be enough room in the head for the heat sinking required at 2A.

Unless you want a 30/90 duty cycle. :tinfoil:

Of course, you could implement TEC cooling and/or a mini fan.

I'm driving the M140 in my custom build heatsink with 1,9A ~2400mW stable output and a nearly continuous duty cycle (like 30min on 5min off for better lifetime I mostly use ~15min on 5min off more is possible)

 

[Bionic-Badger]

The LM317 is only meant for up to 1.5A anyway, and only if you're using the TO-220 package with a heatsink (if you're using a smaller one, it'll be less). You'll need a different chip if you want to push past that (such as the 1.6A the M140 can handle). I'd suggest using a boost/buck driver as others have suggested. They're more power-efficient, and usually easier to get to the right output.

 

[chipdouglas]

If you really need to use 9V batteries then take 5 of them and put them in parallel, that way each of them only has to supply 200mA of current, which they can handle a lot better than 1A.

This is a bad idea. Most 9v batts ( the rectangular ones ) are reared from 50-150 mAh.

We don't even use these batteries for 100ma builds.

Michael

 

[jsteg1981]

Ok here is an update on my laser.

I have made a driver circuit with the LM317, two 2.2 ohm 2W resistors and a 16V 10uF capacitor. I have soldered all that on to a small circuit board. The resistors are parallel.

When the laser is first powered on, it is at 1.05A for about a half of a second then drops to about 300-350mA. After about 15 seconds, it would jump back up to about 600mA. It is also pulsing. You can only tell it is pulsing by quickly moving it around. As in it looks like the laser is jumping and not fluid lines.

Now it does not jump back up... I hear the pulsing is a sign of an overheating driver. How can I test my LM317? It is heatsinked but at what temp does it fail?

Attached it a picture of the driver. I removed the capacitor thinking it might have something to do with it. I plan on building another driver circuit tonight.

Any ideas?