Step 2: The schematic

This schematic is a little different from the ones you'll mostly find on the internet.

It doesn't use a capacitor for flattening the output voltage of the LM317T because the output signal is already perfect.
It's also dangerous to use because when you remove the diode, the capacitor will charge to higher voltages as allowed for the diode, and when you attach it again your diode will be destroyed.

We also don't use an inverse parallel diode because that's not required. Your LM317T can't give negative voltages. Even if it did, the laser diode is a diode which means it can take negative voltages (-2V).
And even if your LM317T would somehow create negative voltages, your diode would die anyway because it means the regulator is broken; no current regulation means dead diode. I don't see why people put diodes over there.

You can use a 9V battery or an external power input for this laser burner (choose between both with S1).

When using the battery, all is ok, but when you use the external input you should keep this in mind:
If your diode works at around 4V and your voltage source is 9V then the LM will have to dissipate the remaining 3.75V by converting it into heat.
Dissipating 5V is allright.
The LM is made to handle a maximum voltage of 40VDC. If you would do that, and your diode still works around 4V then your LM will have to convert the remaining 34.75V into heat. This is possible - with an epic heatsink - but we want to keep things compact right?
If you use a small heatsink and 40V input, then I ensure you your LM will be fried. (maximum junction temperature for the LM317T is 150°C, 302°F)

If you want to have an extra trim potentiometer for inside the casing, I suggest using a 50ohm potentiometer - 250mW.

D1 will be protecting our circuit from inverted polarity.
D2 is the laser diode.
R1 will protect R2 from being toasted (current limiter).
R2 is the potentiometer which will control the current trough D2.
Iadj is the adjustment current from the LM317T (see datasheet ).
<p>I just get artictle about &lt;a href=&quot;http://911electronic.com/tunnel-diode-characteristic-symbol-definition/&quot;&gt;tunnel diode&lt;/a&gt;, if you need to get more information about this electronic device check this</p>
Can i use a 1n4148 diode instead of the 1n4007? <br>
Hey, <br>You can use it, but because the maximum current is only 200mA, if you will be using strong laser diodes, I suggest you put two 1n4148's in parallel, so that they can handle 400mA.
<p>NOTE on DIODE in PARALLEL: Resistance decreases in diodes as their temperature increases which is why diodes, LED's, Laser Diodes, etc, need to be CURRENT LIMITED... If two diodes are wired in parallel, whichever one is hottest will pull the most current, get hot and burn out... then, due to burned diode, all load would be put on the next diode in parallel...</p><p>(The lm317 is excellent for limiting current to any LED / Transistors / Laser Diodes)<br><br>Hope this helps! <br><br>:)<br> </p>
<p>No. The 4148 is a low power signal diode and the 400x series are made for at least 1 amp of current.</p>
<p>Hi there, I'm trying to build laser driver from DVD laser diode for engraving machine... here is my fritzing file, can you tell me where I'm going wrong</p><p><a href="http://adverta.com.mk/test/arduino/laser" rel="nofollow">http://adverta.com.mk/test/arduino/laser</a></p>
Be Straight Pls Am New R1 Or D1 And Voltage
Do a NTE958 also work? <br>what voltage requires a 2 w laser?
<p>would be cool if you'd give more details</p><p>what voltage ? amps ? polarity ?</p>
can i make a burning laser from a key chain laser pointer by fed it more current if not why and laser watt depend upon what ? why a specific laser diode is use
<p>That's like asking why can't you just feed more current to a desk lamp light bulb to turn it into a floodlight or spotlight. They aren't built to accept that much current, so they will blow out. Lasers are developed to emit light with a certain intensity <strong>at a certain current</strong>, and this intensity transfers energy. That process is basically the power of the laser, and power is measured in watts. Even if you get the most powerful laser in the world, you can't simply feed it more current to make it more powerful, as you will still blow it out after you exceed the maximum current the diode can handle. If you want a fun little laser toy it will have a cheap, weak diode of 5 milliwatts, or .005 watts. If you want a laser that is capable of burning something, you need at least 100mW, but even then it will be slow. The more watts your laser diode is, the more powerful it will be and the quicker you can burn, melt, or pop things!</p>
<p>Saw quite a couple of these instructional videos and everyone's saying to extract the diode and build a driver for it on another heatsink/casing.</p><p>But I just wonder why not just leave the diode as it is in the laser carriage assembly and simply power it up with whatever ribbon cables it is attached to? </p><p>Saves all the trouble don't it?</p>
<p>Since nobody else answered you, I'll try and answer. I believe that the dvd drive only uses short, low powered pulses for writing to a disc, and also the lens build into the carriage focuses at 3mm or so from the lens, which would not make ANY kind of beam. It is also non adjustable, so you're stuck with tat short focal length. It probably can't take higher current to do real burning jobs with the minimal heatsinking that the carriage would have, as well.</p><p>Most people use an aixiz laser housing which is cheap and solves 2 of those problems above: heat and focusing lens. All that's left after getting the diode into the housing is building a driver so you can supply a clean current to the diode, and you're good! The housing is tiny too so you can fit it into things like a flashlight or project box easily.</p>
<p>I made my own driver with an lm317 and a potentiometer that had adjustable voltage. I tested it on an led and a 5mW laser diode and found it to be working, but then when I hooked up my dvd drive diode it got dim after about 20 seconds of use with the driver set to 2.8 volts. Is limiting voltage the wrong thing to do? Your driver is only slightly different than mine, but I'm wondering how if I limit only the current, the 9 volts from my battery won't blow the diode out instantly? Also, I'm correct in assuming that you can't regulate both the voltage and the current at the same time, right?</p>
<p>please update </p>
<p>where do you get the lens</p>
<p>Why is it that when i apply 9V battery DC directly on the DVD laser diode it is not light up? Am i doing it over voltage and fried the diode?</p>
<p>People, please realize that all LEDs and Laser Diodes must be current limited or they will burn out instantly! At a minimum they should have a correct resistor in series with them to limit the current to the max allowable shown by the spec sheet. Even better is to use a current regulator as shown in this Instructable.</p>
<p>you actual broke it, he uses a current limitation, that means that thevoltage steps down until a specified current will flow.</p>
<p>Hi , i have cd burner,..are its can be used for laser burn...?</p>
<p>How can I convert this to work on a battery bank with 4 AA batteries? I'm making a laser gun and there is already a space in the casing for this bank. I would rather use that than a 9V. Or, better yet, convert it so that it can alternate use between the 9V and the battery bank.</p>
<p>It will work on 4AA batteries just as well as a 9V if the diode drop is less than 4V as it often is. (Depends on what laser diode you end up with. Hard to tell when you are extracting them from a DVD burner.)</p>
<p>I looked in Radioshack and could not find a 3.3ohm resistor. What other names are there for it?</p>
<p>Go to Jameco.com and they will have it.</p>
its called amazon
I've made the circuit and tested it, and it appears either my LM317 is broken or I don't have it wired properly. Can anyone show my how they have their LM317 wired?
<p>i should be able to connect the diode straight to my lab supply, right? i can tune the supply to the hundredth of a volt and the thousandth of an amp.</p>
Would a 7805 regulator work here?
a lm7805 is a voltage regulator not a current regulator.
Not really. The voltage over the potentiometer and resistor (5v in this case) would be too high. When you increase the output current, the power dissipation in the potentiometer will just fry it.
<p>In the instructions it said you could use one.</p>
<p>Where can I find an lm317</p>
<p>Great instructable! Easy to follow but not dumbed down. I used your circuit today to make a laser spirograph (although I am using a laser module meant to be powered by batteries instead of a bare laser diode) and it worked just fine!</p>
hi. is a dvd diode exact the wavelenght of 650nm or is there an range? I just want to find the glasses maching de dvd burn diode wavelength and want to be very sure there is no IR.
<p>heyy<br>plz help me to make a circuit for powerful laser which can burn plastic sheets of almost the thickness of 3-4 paper sheets<br>n of what power the laser diode should be???</p><p>thnx in advance</p>
<p>heyy<br>plz help me to make a circuit for powerful laser which can burn plastic sheets of almost the thickness of 3-4 paper sheets<br>n of what power the laser diode should be???</p><p>thnx in advance</p>
Hey electorials! Loved the instructable.....can this thing cut acrylic ,plastic boxes etc. as well??
im using a diode from a dvd burn... but it not burn!!! why? can you help me? im usin a circuit with LM317
cool gonna make one <br>
I got 6.88 volts as the output to go to the laser. Is this fine or should I put a regulator on it?
Hi, I'm wondering about the limiting potentiometer. Do you connect it exactly like the one for regulating the intensity? And do you still use 100ohm for regulating or do you change the value?<br><br>greetings, SpecieS
hi,<br>I still use the same value, 100ohm (but I think 50ohm would be a little better, not sure).<br>It is indeed connected exactly the same, and placed in series.
Thanks for your fast answer. I found some 50ohm 1/2watt precision trimmer, which would be perfect for the limiting job :D<br>A 300ohm resistor in parallel to the regulating potentiometer would reduce its maximum resistance to 75ohm. Seems to be a good compromise :)<br><br>greetings, SpecieS
huh?<br>You say 'reduce' it's maximum resistance, but you say it goes from 50 to 75 then?<br><br>Indeed, a 50ohm trimmer would be nice.<br>When adding a resistor in parallel over it, you'll Decrease it's resistance, not increase to 75.<br>And also, when you added a resistor in parallel, the track resistance won't e linear anymore.<br><br>You don't need to add a parallel resistor, the 50ohm trimmer is perfect.
Oh, you misunderstood what I said. I don't want to decrease the trimmers resistance but the regulating potentiometers resistance from 100 to 75ohm.
Ahh yes, I see now.<br>but I don't think you'll get &quot;more precision&quot; out of it by doing that because it will make the slider non linear.<br><br>At the lowest resistance values, it will change faster now.
Indeed, it makes it non linear, but I've inspected the function in kmplot and the graph is almost linear: http://img836.imageshack.us/img836/6051/resistancegraph.png<br><br>btw, I've made some new schematics including the second potentiometer using Eagle: http://img845.imageshack.us/img845/3899/schematicslaser.jpg<br>You may attach it to the instructable if you want.

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Bio: I'm really fascinated by science! From when I was young I've been curious about how stuff works and how I can create those ... More »
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