Complete laser noob... Please help!!!

I am sorry if this has been covered previously. As you guys can tell from the thread title, I am a complete laser noob. I have been watching tons of videos on youtube of different burning lasers. I recently purchased a 2W 445nm M140 laser diode and housing from ebay. I will paste link later. I only bought the 2W as it was a few bucks more than a 1W. However, I only want to run it at 1W since this is my first build and do not want to burn it out.

I have seen many sources that state you can successfully run the laser with an LM317 driver. My host is a Smith & Wesson LED flashlight that I had laying around. The power source is three AAAs. I have build the driver using an LM317 as a current regulator. I have used a 1 ohm resistor to get it as close to 1 watt as possible (the resistor test at 1.4 ohms). I get a very dim beam. A voltage test shows 1.2V and I get nothing when testing the current. If the calculations are correct, I need about one amp to achieve one watt (1.25V * 1A = 1.25W). I then calculated 1.25V / 1A = 1.25 ohm resistor. Shouldn't that be a nice bright beam?

Can someone tell me what I am doing wrong? Do I need a more sophisticated driver?

Link for the diode and housing I purchased-

2W 445nm M140 Blue Laser Diode in Copper Module w Leads Three Element Glass | eBay

I do apologize if this has been discussed. I did not see what I was looking for in other threads. Please point me to the correct thread if there is another discussing this issue.

Also, If I bypass the LM317 and just run one AAA in series with the 1 ohm (1.4 ohm) resistor, it does not light up at all. Not sure if that is relevant.

Thank you in advance for the feedback and patience.

I would also like to add that I am dead set on building this thing from scratch as much as I can. That is why I am using the host that I picked. If any pictures would help, please let me know.

You are drastically under powering that diode. You are providing providing a 1.5V source, and the diode is starving. It is nothing for the M-140 445nm diode to drop Vf of 5V. You should be using 2 x 3.7V lithium Ion cells (or equivelent). Your driver will eat what the diode doesn't drop at the regulated current level.

I know you are set on building this yourself. I just hope you have a heat sink made for the host you are using. This diode produces a lot of heat, and I cannot stress the importance of cooling enough.

As for the driver, an LM317 will work, and your calculations are correct for the current. At 1 Amp you should get about 800-850 mW with that three element glass lens. There are better options then the LM317 (more efficient) when you are ready. Do some searching on the forums and you will find lots of options, from DIY to ready made drivers.

Cheers!

The heatstink I have, I made from a CPU heatsink. It is about 1.5in thick. It fits almost perfectly into the front of the host. As for the host itself, it is made from aluminum as well. My assumption led me to believe the host would act as the heatsink as well. The diode housing is copper.

I was told by another member that I should use three 10440 batteries. My local battery shop does not stock them. Any other recommendations?

jsteg1981 said:

The heatstink I have, I made from a CPU heatsink. It is about 1.5in thick. It fits almost perfectly into the front of the host. As for the host itself, it is made from aluminum as well. My assumption led me to believe the host would act as the heatsink as well. The diode housing is copper.

I was told by another member that I should use three 10440 batteries. My local battery shop does not stock them. Any other recommendations?

Click to expand...

The 10440 battery is a 3.6/3.7V Lithium Ion battery that is the same physical size as the AAA. It makes for a good choice for you because your hose is already set up for 3 AAA batteries. That said, providing 11+ volts means that your LM317 will have more extra voltage to dissipate. What I mean is, the Laser Diode will only draw what it needs for voltage at the selected current, and the rest of the voltage will need to be stripped away by the driver. This is how current regulators work. The side effect of this is more heat from the driver.

Even 3 standard AAA batteries (4.5V total) will struggle to provide enough voltage to your diode. It is worth ordering some 10440's and waiting.

The other thing to consider is that you may have somehow killed your diode. Either while soldering it all together, or while experimenting. You can easily see if your driver is working. Wire a 3W resistor on the output and see if it is drawing the 1A you are seeking. In fact, for now you can use a regulated power supply to make sure your input voltage is high enough. If you have one that is. If the driver is running properly, and you have a good/adequate power source, that only leaves your diode.

Good luck.

I do not have a regulated power supply. I could always use and AC adapter and throw in some resistors suppose. The diode came presoldered so I sure hope the person that soldered it did not kill it. I have the LM317 heatsinked as well. It is a small heatsink though. I have been trying to brainstorm as to where I could attach the driver to the host as the host is aluminum. I have not done the math yet on how many watts that little driver has to dissipate.

Today I bought a 10W 1 ohm resistor to play with before hunting down a 1-2W resistor. Still not pulling much due to the massive voltage drop. I suppose a 9V battery could work for now???

Those 9V batteries can't supply much current. They're made of 6x AAAA batteries in series, so they they're only good for stuff like remote controls and smoke detectors. Worse, those Alkaline cells have reduced lifetime if they supply too much current, so it would die off too quickly.

You should really get some LiPo cells to power your laser. Also you might consider getting a boost-type driver for the laser rather than the LM317 driver. The LM317 is nice for getting something working on a desk, but it sucks to power in a portable host as you need 2.5V or so over the forward voltage of your laser diode.

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.

jsteg1981 said:

I do not have a regulated power supply. I could always use and AC adapter and throw in some resistors suppose. The diode came presoldered so I sure hope the person that soldered it did not kill it. I have the LM317 heatsinked as well. It is a small heatsink though. I have been trying to brainstorm as to where I could attach the driver to the host as the host is aluminum. I have not done the math yet on how many watts that little driver has to dissipate.

Today I bought a 10W 1 ohm resistor to play with before hunting down a 1-2W resistor. Still not pulling much due to the massive voltage drop. I suppose a 9V battery could work for now???

Click to expand...

Laser diodes are very static sensitive, and if you do not use proper ESD precautions it is possible to fry one while hooking those pre-soldered wires up (I use an ESD strap tied to a known good ground) to your driver and host. Those wires are still a path back to the diode. You do not need to see or hear a spark for ESD damage to have occurred. DTR solders the wires from the diode together for shipping to prevent ESD damage while in transit to you.


The resistor I suggested is not to set up the current level on the LM317, but rather to test the output of your driver to confirm you are indeed getting 1 Amp of current.

A 10 Watt 1 Ohm resistor will drop the same amount of voltage across it as a 1 Ohm 1/4 Watt. The only purpose for using a higher wattage resistor is to prevent it from heating up and burning out. (Ohm's law P=V*I) If you plan on running your driver at 1 Amp (and you want to test/confirm the output of that driver) you will need the load to be able to handle the amount of power (watts) consumed by the resistor. Which will vary depending on the output voltage. This is basic DC Circuit 101 level information.

I know you are excited, and want to build your own stuff. That is admirable, but a off the shelf driver solution to get your first build working is not a bad idea. If you had a 1 Amp X-Drive and battery enough to provide enough voltage and current on hand, you could use that to verify your diode is still healthy.

You may have killed your diode with your experiments (ESD etc.)
I strongly recommend you to inform yourself enough before doing anything like hooking up the diode directly to a power supply (Battery, Bench PSU doesn't matter all are dangerous if you not know exactly what you are doing)

And last but not least I wouldn't use the LM317 Driver !
for an 300mW 650nm Build the LM317 may be sweet but definitely not for an M140 !
Think about an boost driver or use the L200 Driver with two 18650 like I did in my Build
http://laserpointerforums.com/f65/m...d-all-myself-2-5w-445nm-blue-laser-79179.html

Brief update to my findings today.

LD is healthy and burning. I used a 9V battery and 5 ohms of resistance.

I ended up with 3.8V and 230ma for a whopping 874mW. It did slowly burn electrical tape. I ran it for about a minute. Nothing got very hot (ie the driver and LD well the housing at least).

Now if I did purchase a premade driver, which one would you recommend for 1.5W while using three 10440s?

Keep in mind running a diode directly off a battery is not recommended and can damage the diode. I don't cover losses of diodes run in this manner. Good thing is the 9V "may" not be able to deliver enough current to kill the 445.

On the driver 1.5A is a perfectly fine current for the diode. Which driver is it?

I am using an LM317 driver setup. The LM317 is heat sinked. I do not completely reject the idea of an off-the-shelf driver but only if I really do need one.

DTR said:

Keep in mind running a diode directly off a battery is not recommended and can damage the diode. I don't cover losses of diodes run in this manner.

Click to expand...

He is right don't do it! I just killed a 405nm because I couldn't be patient enough to wait for the driver :cryyy:

I even knew better which was the dumb part, I tapped in once with an IMR 18350 and it worked than I adjusted the lens tapped it again and there went $50....

jsteg1981 said:

I am using an LM317 driver setup. The LM317 is heat sinked. I do not completely reject the idea of an off-the-shelf driver but only if I really do need one.

Click to expand...

If that is the case with a linear like the LM317 I would get or make a AAA spacer and lose one of the three 10440's as it is just going to drop the full voltage of the third 10440 as heat with no capacity advantage unlike a buck driver where the extra voltage will decrease the current draw increasing capacity and you will have to deal with all that extra heat.:beer:

It is not running directly off of a battery. I am using the LM317 as the driver. I thought I mentioned that before... Sorry

That being said, with the LM317 in place, the LD is getting 3.8V and 230mA for the total of 874mW. I hope that helps to clear things up.

In my original post to start this thread I did mention connecting directly to one AAA. I do know better to run a LD directly from a battery as I killed a red LD running directly from a 9V. That was my first LD extraction and test. I just figured 1.5V from the AAA would light it up. I was not aware of the massive voltage drop with the 445nm LDs.

So then the LM317 driver is going to be ok?