## Step 5: Step 3: Driver

What's this?
This is used to regulate the current flowing through the diode.

Do I need this?
YES! You must NEVER connect the LD directly to the power supply because it WILL die!

Can I just use a resistor?
Theoretically yes, but the current will not stay constant as the components heat up and the battery voltage decreases and this can shorten the diode's life.

But kipkay didn't use any driver...
Why do you think we have to deal with n00bs crying about their dead Laser Burning Flashlight Hack? (Just read the text above...)

UPDATE
A lot of people ask me about the diode's forward voltage stuff. This is a constant current driver. That means, it will adjust it's output voltage in order to keep the optput current fixed. So, it doesn't matter if you connect a red (2.2V), IR (2V), 405nm or a 445nm (>4V), as long as your power supply's voltage is above the diode's voltage + 1.5V, your laser will be running fine at the set current.
Also, the answer to question: "What voltage is diode XY?" can't be answered directly. Every diode's forward voltage (Vf) depends on her type and on the current. For example, a LPC-815 has Vf from 1.8V up to about 3.2V, as the current increases. Every diode has a PIV plot, which describes it's dependancy between the current, optical power and voltage. Google your diode's PIV plot, such as "LPC-815 PIV" or "22x red PIV" and so on.
Since we're building a red laser here (based on LPC-815), here's the PIV plot for LPC-815: http://www.diy-lasers.com/images/LEC_LPC-815-red.png

You can either buy one or build one (if you can)
the most common commercially sold drivers are:
and

The most common DIY driver is called DDL driver and it uses LM317 as current regulator.

you will also need a thing called TEST LOAD, which consists of 4 1N4007 diodes and 1 1ohm resistor wired in series (check the pics). To use it, connect the output terminals of driver to test load (+ on the diode's anode, - to the resistor) and measure the voltage across the resistor. With 1ohm resistor, 1mV of voltage equals to 1mA flowing through the setup. Now rotate the small potentiometer, until the DMM reading matches your desired current.

recommended currens for various diodes:
16x...200-250mA...<200mW
22x...300-400mA...250-300mW
how to make small laser hair removal machine. Like this handy machine or very laser hair removal machine
<p>I did'nt see it mentioned anywhere about keeping the tab on the LM317 away from the laser diode case.</p><p>The tab is connected to the Positive Output of the 317 and the laser case is Negative/Ground. If they touch you would get a short circuit.</p><p>In one of your photos it looks like they are touching each other.</p>
Yes, that's right. It's not shown very well in that photo (step 7, photo 2), but the LM317 is actually insulated by a heat sink gasket and the bolt also has an plastic insulating washer.
<p>Ok 3zuli. Thats good to know.</p>
<p>I'm trying to reproduce the laser driver. It turns on but the laser doesn't burn anything.</p><p>The design is the same and the laser switch on and it can get to 240mA. If I change the 2 resistors (10ohms) for 3 I can have 350mA. Even like that It doesn't burn... :(</p><p>My AIXIZ module is <a href="http://www.aliexpress.com/item/Hot-Sale-650nm-5mW-Line-Linear-Red-Laser-Module-Head-Glass-Lens-Focusable-Industrial-Class-Free/32528710798.html" rel="nofollow">this</a></p><p>Thanks for any help</p>
If you're sure that you used a diode from a DVD-RW drive (not a DVD-ROM, those don't have enough power), then it looks like the diode is damaged. It could have been either mechanical or electrostatic damage (ESD) during removing the diode from the drive, ESD or overheating during soldering, or the initial current was simply set too high and it destroyed the diode. After any of those events, the laser diode breaks down and keeps operating as a LED diode, but has minimal output power, so that's why it doesn't burn anything. Just get a new DVD-RW drive (or just the laser assembly itself) and try again, eventually you'll get it right :)
<p>Hi,</p><p>can someone help me here please ?</p><p>I had 4 red laser diodes form DVD readers/burners. I used exacly this LM317 driver</p><p><a href="http://laserpointerforums.com/attachments/f44/33304d1308798339-small-modification-lm317-drivers-driver-250ma-out.jpg" rel="nofollow">http://laserpointerforums.com/attachments/f44/33304d1308798339-small-modification-lm317-drivers-driver-250ma-out.jpg</a></p><p>connected to 7.5V 1.5A power supply.</p><p>I set the driver to produce around 60mA. All 4 diodes were OK. The problem was all 4 diodes after 20sec just reduced their brightness for around 10%. After 2 diodes i thought the diodes just getting damaged from heat. But i tried to hold the third and fourth diode in hand without heatsink and they weren't even heating ! And same thing happened.</p><p>This issue is permanent for the diodes and it happened to me also with more powerful IR diode.</p><p>Any ideas ?</p><p>Thanks a lot !</p>
<p>You must know the operational power of the diode and adjust control circuit accordingly.</p><p>When you slightly damage laser diode, it starts to function as a normal LED (it becomes trash). Perhaps that is what happened to you and you didn't notice heat output after.</p><p>Also LM317 adjusts voltage so that correct current flows through and if diodes's resistance went up, LM317 could've run out of input voltage (diode demanded more than 7.5V - 1.7V [Lm317 takes that much for itself]).</p>
<p>You must know the operational power of the diode and adjust control circuit accordingly.</p><p>When you slightly damage laser diode, it starts to function as a normal LED (it becomes trash). Perhaps that is what happened to you and you didn't notice heat output after.</p><p>Also LM317 adjusts voltage so that correct current flows through and if diodes's resistance went up, LM317 could've run out of input voltage (diode demanded more than 7.5V - 1.7V [Lm317 takes that much for itself]).</p>
<p>60 mA is probably not enough to power your diodes. The current may differ between diodes, so check the datasheets.</p>
<p>I know almost nothing about lasers but maybe the voltage they were getting was too high</p>
<p>Great job man! hope you keep it up</p>
<p>hi</p><p>how to connect three legs of VR</p><p>thanks</p>
<p>Hi, This is the &quot;Sony DVD-RW : DRI-190A&quot; laser part which wirtes DVDs on 20x, i want its laser for using in mini CNC machine, but there is two laser diode in this model, i cant distinguish which one should i use, and i dont know about the model of laser diode too, any idea?<br>Left one, or Right one?<br><br><br>&lt;I know i can test them and select the stronger one, but i just wanted your ideas&gt;</p>
<p>just for clarification, how is the test circuit suppose to be used? just hook it up the the driver circuit to check the resistance right?</p>
<p>hello sir , <br>i am working on same project</p><p>i used dvd rw laser for my project. I follow the circuit diagram given above but laser is not upto the mark not focus and not burning paper or any other things. Is this problem is due to lens that i havent used yet or any other thing ? </p><p>plz help</p>
You need to use a focusing lens in order for the laser to burn stuff. Otherwise you just get a wide beam which is very weak.
<p>I Made it! Actually I made all this laser using a NDV 4542 405nm diode at 120mA using this driver. I also made gerbers (PCB schematic) for this driver and uploaded it in this comment.</p><p>You can see my build (CNC Laser Engraver) in my profile.</p>
<p>Your LM317T schematic is WRONG, my friend!<br><br><a href="http://vakits.com/sites/default/files/imagecache/product_full/LM317T%20Application%20%2526%20TO-220.JPG" rel="nofollow">http://vakits.com/sites/default/files/imagecache/p...</a><br><br>Middle leg is the output leg.</p>
<p>This schematic is OK. Your schematic is the LM317 as a constant <strong>voltage</strong> source, which can not be used to drive laser diodes. </p><p>In this case the LM317 is connected as a constant<strong> current</strong> source: <a href="http://www.ae5d.com/images/Lim.png" rel="nofollow"> http://www.ae5d.com/images/Lim.png</a></p><p>The current goes from the OUT pin, passes through the resistors creating a voltage drop, which is then sensed by the ADJ pin and compared to the internal 1.25V reference. LM317 will adjust its output voltage to get 1.25V on its ADJ pin, which in this connection results in a constant current supply. </p>
<p>I'm looking to purchase a lazertag system to start a lazertag business, <br>would you be able to produce or lead me to the guns and equipment I need <br> that would be safe and certifiable, that would be a cheaper option than <br> the \$600/gun price range that I've seen advertised by the lazertag <br>manufacturers? email if so at ulrichinvesting@gmail.com</p>
<p>This is the cheapest lasertag I know about: <a href="https://www.kickstarter.com/projects/skirmos/skirmos-open-source-laser-tag" rel="nofollow"> https://www.kickstarter.com/projects/skirmos/skir... <br></a></p><p><a href="http://www.skirmos.com/index.htm" rel="nofollow">http://www.skirmos.com/index.htm</a></p><p>It will cost \$119 per gun (DIY kit), but it's still in development. However if you want to make a business, I would rather rely on ready-made lasertag systems which are already certified, reliable and safe to use. As a lasertag business, the last thing you want to deal with are blind customers.</p>
PLZZZZZ clarify my doubts<br><br><br>1&gt;want to know that if I use Li-Ion batteries i.e; 18650 which are 3.7v 2600maH,then I have to use 3 of them connected in Series is that right(about 11.1 v )(since the total consumption will be about 7.2v),but these batteries comes with pcb protection so when I will be using this laser will the pcb should posses any problem.Secondly want to know that if this driver can handle 2600mah.<br><br>2&gt;Then in case 14500 which is standard AA(1.5)then have to use 5 of them I guess,plz clarify if I am right or wrong.<br><br>3&gt;Can u plz give the names of the chargers which charges these batteries,1 by 1 charging will not be a problem for me.<br><br>4&gt;plz suggest the best lion battery manufacturers. I went to this site(http://www.candlepowerforums.com/vb/showthread.php?257543-LiIon-18650-battery-comparison)but cant decide which one to purchase.<br><br>Thankx in advance<br><br>
1. what diode are you using? because for red or IR laser 2 LiIon's are enough, but for bluray or 445nm you need 3 batteries. Also, don't forget to properly heatsink the LM317, it will get toasty ;) The protection PCB is mostly your friend, it just monitors the battery and keeps it from under- and overcharging and disconnects the load, if the current is too big. The 2600mAh number is the capacity of battery, the higher, the better - the more power can be stored inside and the longer is the runtime.<br> <br> 2. 14500's are 3.7V LiIon's too, so you have to use 2 or 3 of them<br> <br> 3. I'm using this one: http://www.dealextreme.com/p/trustfire-tr-001-multi-purpose-lithium-battery-charger-12594 It's a bit slow but works, this one is quick charger (and can fit some bigger batteries too): http://www.dealextreme.com/p/ultrafire-wf-188-rapid-charger-for-3-2v-3-7v-lithium-batteries-100-240v-44091<br> <br> 4. You don't have to use those \$15 AW IMR batteries, in fact those cheap 18650's and 14500's I linked in this step are good enough (I'm using both, drawing 1.5A from 18650 and 0.8A from 2 14500's in series and they preform well)<br> hope I helped you :)
<p>I'm looking to purchase a lazertag system to start a lazertag business, <br>would you be able to produce or lead me to the guns and equipment I need <br> that would be safe and certifiable, that would be a cheaper option than <br> the \$600/gun price range that I've seen advertised by the lazertag <br>manufacturers? email if so at ulrichinvesting@gmail.com</p>
can I use the G9105 regulator???
<p>G9105 is a 5V fixed voltage regulator. I've seen some people build laser drivers using fixed regulators, but I don't think it's the best idea. Adjustable regulators such as LM317 are way better for this. If you are interested in the low dropout voltage, try the LM1117 which is a low-dropout variant of LM317.</p>
<p>I cant get a 35mw laser diode burning with the standard laser circuit ie.9v lm31t.</p><p>what could the problem be?</p>
<p>35mW is not enough for burning. Generally you need at least 100mW to burn stuff, so I recommend you to buy a stronger diode.</p>
for metal cutting what i can do...?
Hi, I want to build a ~150mW 532nm green laser, but am not quite sure how to. <br>I have a flashlight housing with 2x 3.7V batteries, which i bet I can fit the laser into <br>I want to buy all the pieces online so that I can assemble the laser when they arrive, <br>but seems like no one is selling a laser diode nor driver, <br>I am want to spend &lt;35\$, <br>is this possible? if so, can you reffer to a ebay seller, or maybe share some links?
This is not possible for &lt; \$35 (unless you get the module as a gift from someone :D ). Just the laser module will cost you \$40-50, for example this one: http://dx.com/p/200mw-532nm-green-laser-module-3v-11-9mm-26891?r=93098389 , which should output 100-150mW.<br> These modules can't handle 2 3.7V batteries, so you can either replace the original driver with one that can run from 7.4V, or you can build a spacer that will fit inside the battery tube and will replace one of the batteries, so that you only get 3.7V. It's also recommended to connect a diode (1N4007) in series with the module, because some modules might get burned from fully charged LiIon cells (4.2V) and the diode reduces the voltage by about 0.6V.<br> I recommend you to go to laserpointerforums.com and view the Green lasers section and try searching for &quot;green laser tutorial&quot; or so, I am sure you will find lots of informaton and ideas for your build :)
what is the voltage &amp; Amps of a red laser diode? <br>(I am using a 22x HP DVD R\W Drive red laser diode...) <br>
16x...200-250mA...&lt;200mW <br>22x...300-400mA...250-300mW <br>Start at 300mA to be safe.
please tell me the voltage of laser diode<br> 3v,<br> 4v<br> or +7.2V
what diode are you using?
please tell me the voltage of laser burner
hi there <br><br>i did every thing as you did but i can't get the laser to burn, could you please help me? i used the same parts (laser diode, parts for the driver).<br><br>
1. what PSU are you using?<br>2. is the laser focused?
I am using a dell PS-5161-1D PSU<br>Output: at 5V, max 11A, 85W max<br> at 12V, 9A max, 160W max.<br>i have tested at both voltage. and the beam is focused
do u really need to use a module?
well, you don't have to, but it's just so much easier to use one, and they are pretty cheap (around \$4)
can i use the power from a tomcat torch and/or a 3v power suply?
can i connect a 3v power supply to my diode without anything else mabey a diode?
Sorry, but I have one more question. When measuring the voltage to adjust my driver's pot, should the power supply be on? I imagine it should, but I just want to make sure since the power supply comes in the step after you adjust your driver. Maybe I worry too much, but I don't want to fry my diode. :)
of course, the power supply has to be powered on while adjusting the current
Yea, that was a little stupid of me. Just making sure.
I have been looking for a resistor for the test load.&nbsp; I found over a hundred 1 ohm resistors on digikey, and I'm kinda confused.&nbsp; Could you give me some more info on which to use, or does it not matter for this application as long as it is 1 ohm?<br>
you should use a resistor that is rated for at least 1W of power. the common 1/4 or 1/2W resistors can't handle bigger currents. so get a 1ohm 1W (or any higher wattage)
Thank you!