Which Resistor? Help

[theacexer]

I have a 20X DVD burner diode and a "650nm 5mw 12mm 30mm Module", so i dont just hook straight up 2 AAA batts, between the batteries and the diode what kind of Resistor should i put in, 1/4 watt, 1/2 watt? 3.3, 3.9, 2K???

want it to burn but not risk too much of dying soon, between 150-200mw.


Looking for a resistor that would restrict the batteries to about 240ma if anyone can help.

 

[Aseras]

Ohm's law... http://en.wikipedia.org/wiki/Ohm's_law

2xAAA = 1.5v*2, or 3 volts , you want 240ma of current so you want 12.5 ohm's resistance.

 

[theacexer]

really appreciate the response, im going to radio shack to get the resistor, do i want the 1/2 or 1/4 watt resistors and which one, 3.3 3.9, i was told 3.9 is that right?

 

[Gazoo]

really appreciate the response, im going to radio shack to get the resistor, do i want the 1/2 or 1/4 watt resistors and which one, 3.3 3.9, i was told 3.9 is that right?

Watts = Volts X Amps. So you will want to get 1 watt 12 ohm resistors. However since each diode is a bit different, I would recommend getting an assortment of something between 5 ohm and 20 ohms so you don't have to keep running back and forth. I have never been able to get the output power I want with just two NIMH's. It always takes three. But if you don't want to risk it, then use two batteries. You will also want a capacitor to prevent surges to the diode. I use a 100uF, 25 volt electrolytic capacitor. The values for the capacitir are not critical. Make sure you hook up the capacitor in the correct polarity or you will end up with a firecracker..Lol.

 

[Gazoo]

Looks like the closest thing RS has in a 1 watt is a 10 ohm resistor. You can use 2 1/2 watt resistors connected in parallel. Or go with the 1 watt resistor RS has and find some others on line. RS is high priced in comparison to online places, but they do come in handy.

 

[theacexer]

so you wouldnt reccomend just straight hooking up 2 AAA's to the diode i have housed in a laser module???

 

[Gazoo]

so you wouldnt reccomend just straight hooking up 2 AAA's to the diode i have housed in a laser module???

You can but you risk losing the diode. Many of us have learned the hard way. I do recommend using a resistor and a capacitor.

 

[theacexer]

i really appreciate the help, ive already purchased a 60$ dvd burner and got the diode, now have to extract without breaking, I ordered the laser module from Aixiz, have to extract the diode from that when it arrives and put the new one in, could you tell me exactly which Resistor/Resistors, which capacitor and the best cheapest way to hook them up from parts that are available at radio shack, i would really appreciate that, i just got paid today and the module arrives tomorrow and wanna finish this little project tomorrow. Thank you so much, will send you pics when finished, by the way Gazoo, look here, just put up pictures from a 1000$ camera of my Green laser http://viewmorepics.myspace.com/ind...r.viewPicture&friendID=5945283&albumId=791753

 

[Gazoo]

For 2 batteries, I you will be good with the 1 watt 10 ohm resistor. It might not be the perfect value, but it will get you started and should be a high enough value to keep your diode safe.
Catalog #: 271-151

For the capacitor, RS has a 100uf 35 volt electrolytic that will be good for sure. It might be a bit of an overkill, but better to be safe than sorry.
Catalog #: 272-1028

You will definitely want to be able to measure current. Any DVM will work.

I am still waiting for my modules from Aixiz. I ordered 5 of the smaller ones. Remember you can't use the driver boards because they can only support the low current of the diodes that come with them.

Those are some nice pics you have there. A $1000.00 camera huh. I only have my cell phone camera...lol. And of course it sucks. I don't have a green laser yet. Eventually I will but I really like the red beams.

 

[teaken]

You can also use 3~4 1N4001 or similar diodes in series in place of the laser diode to simulate a ~2.1 to ~2.8 volt drop (from my own research most DVD laser diodes have a forward voltage of 2.5 to 3 volts). Then measure the circuit current this will give you a very good idea of how much current the circuit will deliver to the laser diode.
Of course you could just do some maths but calculations and real world results are often very different esp when using such a variable power supply as batteries.

edit: lol i said parallel instead of series, brain fried...

 

[theacexer]

2 AAA batteries and a 10ohm 1 watt resistor, what kinda mw you think ill get outta my 20x dvd burner diode.

 

[Gazoo]

2 AAA batteries and a 10ohm 1 watt resistor, what kinda mw you think ill get outta my 20x dvd burner diode.

No idea. For one it depends on the batteries. Are you going to use NiMh, alkaline, or lithium? This is another reason you need to be able to measure the current with a meter. If we know how much current the diode is drawing, then we can go from there. It is important to note every diode is a bit different. This is why it is a good idea to get a resistor assortment for doing this the cheap way. For the ultimate, an adjustable driver board that will handle the higher currents is the way to go, but they can be costly.

BTW, once you get the diode out it might be marked with a part number. This will help too.

 

[theacexer]

going to be using regular alkaline AAA's, dont really have much more money to spend, spent most on DVD burner and laser module, its a NexxTech NX2 20X Dvd Burner if that helps at all. module should be in the mail today, really need some help with this. been playin with greens for awhile, could really use more info on what to get, with all the help already, preparing for the oncoming flaming! Lol

 

[Gazoo]

Have you read Kenom's walk through for a DIY laser?

http://www.candlepowerforums.com/vb/showthread.php?t=168964

He posted two videos and the first one shows how to harvest a diode from a DVD-ROM. In the video, I think the second one, he explains how to mount the diode in the module. They are worth watching.

My modules didn't come today either. I am currently using a Meredith module that I have been happy with, but it is large in comparison the the smaller ones I ordered.

Also I sent you a PM...did you receive it?

 

[Hemlock Mike]

While it is true that 3 volts / 240 mA = 12.5 ohms, How did anyone account for the voltage drop of the diode ?? This is a series circuit and the LD "SORTA" acts like a resistor (along with the cells) in this circuit.
Look way back to the Dr_Lava diode GB --- TONS of info there.

Mike

 

[Gazoo]

I got my Aixiz modules today and good grief these things are small...lol. But man am I impressed. Even the diode that comes with it produces a nice bright red dot.

Well here is what I did. I ordered 5 and at the price I wasn't concerned about saving the diode, so I knocked it out...yup destroyed it. I have two brand new diodes I received from heruursciences. I mounted one of those diodes to the module with my vice. The only thing I had small enough to press it in with was a cable end. The part that crimps to the center of cable coax is what I used to press the diode into the module. It went in super tight and I did not use any thermal grease.

Next I found a jack from one of my broken down DVD-Roms and plugged the diode into it. It will fit snug, but I did spread the leads of the diode just a little bit to make it plug in as snug as I could. This is much easier than soldering wires to the diode. And of course it makes it easier to swap out the diode when/if the diode turns into an LED..ha..ha.

Finally I hooked up my capacitor and a 5 ohm resistor to a three cell NiMh battery pack. I tested the current the diode is drawing, around 175ma. But the most amazing part is the lens in these little guys! I was able to light a gray headed match almost instantly. And it lights a safety match instantly. Both were Non sharpied!! Since the current draw of the diode is only 175ma, it is putting out less than 100mw. I will admit this was less than a foot away, and I still have some more experimenting to do. But the bottom line is for the price, these little modules can't be beat.

Here is what I am finding with lenses. I have a diode I took out of a 16X Benq Lightscribe drive mounted in a Meredith module with a glass lens. When I focus it for distance, it is also focused for burning up close. This does not seem to apply to some of the other lenses I have played with including the one in the Aixiz module. With the Aixiz, if focused for burning, it will not be focused for distance, and visa versa. I hope that makes sense. BUT, these lenses when focused for burning are some kind of powerful.

BTW, I can already tell the beam is going to be brighter than the beam coming from my Merideth module when it gets dark. But it will also be smaller in diameter.

 

[Gazoo]

One last little update for now. The voltage going to the diode is 2.68 volts. So you can possibly get by on 2 alkaline batteries and a 1 ohm resistor. I tried it and it worked with my diode. Unfortunately, I have no idea what the specs are for the diode I am working with.

 

[Gazoo]

I had to correct my post above. I am using a 5 ohm resistance with 3 NiMh AA batteries. Sorry about that. I have two 10 ohm resistors connected in parallel...

 

[theacexer]

hey Gazoo, could you take some pics of your setup, I ordered my modules last thursday and there still not here, just checked the mail,

 

[Corona]

You're blowing a lot of power in the resistors. Why 3 cells in series?

The red LD should only drop about 2V so two NiMH cells in series should be adequate, and minimize the wasted power (as heat) in the resistor(s).