Is my assembly correct for burning laser?

I am almost done the DDL circuit (http://laserpointerforums.com/attac...omemade-laser-diode-driver-proto_driver_2.jpg) shown in that link.( I belive its the DDL) Anyway, all i need now is the diode really, besides housing, and i was wondering which one you would suggest to use, out of theses two---

LPC-815 20x DVD burner laser lens assembly w/ red laser diode [LPC-815] - $10.49 : Modwerx Shop

LPC-815 660nm red laser diode - $13.49 : Modwerx Shop

I wasn't sure if the 20x will fit the supply of the driver i built. I am probably going to hook up around 6-9volts for power supply, and i might change out the 10ohm with a 4.5ohm resistor. If i do that, will i put the [diode] in danger?

Those are the same diodes.

20x!
Good Luck with your build.

Definitely the 20x it'll be way more powerful

OutlawZ said:

Definitely the 20x it'll be way more powerful

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Well don't count on visible difference between the two.
But first, let's solve the circuit issue
If you put 4.5 Ohms of resistance, you will end up with ~277 mA delivered to the diode.
That is a bit too much for SCC diode, and not enough for LCC/LOC diodes.
Since you are going with LOC diode, they can take up to 400 mA (with proper cooling). If you put 3 ohms flat, that will give you around 415 mA, and it will be around 250mW of optical power output, give or take.
SCC are best at around 200~250 mA (lottery)
LCC/LOC are about 400mA
Now there are also SOC, which are, I think, good for 300mA of current.

The current provided by DDL (lm317) circuit is calculated by following formula:
( CURRENT ) = 1.25 / (RESISTANCE)
Resistance is between out and adj pins of 317. Current calculated is in A (Amperes), divide by 1000 to get mA.

Good luck with your project!

Those are the same diodes, you just paying $3 to have it harvested.

I'm assuming your still sing the adjustable pot correct? If so, there is no way of telling the current you've set it at untill you get a test load to measure it.

Mohrenberg said:

Those are the same diodes, you just paying $3 to have it harvested.

I'm assuming your still sing the adjustable pot correct? If so, there is no way of telling the current you've set it at untill you get a test load to measure it.

Click to expand...

I disagree with the pot... just put 3 ohms between OUT and ADJ, (or 3.33 maybe...) and you have good current for your diode.

So as seeing all the different thoughts here, i should take out my 10ohm resistor, and replace it with a 3 ohm? I thought i read somewhere that a 4.5ohm would allow the ma to be well above 300, but i think that might have been on the senkate 16x burning diode. Speaking of which, the link i have posted further up, to the unharvested 20x diode--that is different in power output, opposed to the 16x sony? Ive read so many different thoughts from people, and now i am not so sure which one to use. I've heard that the 16x is the way-to-go, an what not. But w/e, using my diy driver, i'll just switch out the 10ohm, with the 3ohm resistor, and i guess i'll use the 20x diode, powered by 2x RCR123. Tell me if you have any better ideas with either diodes or resistors. Thanks!

oh and as for the test load, i just put in an LED, then tested with multimeter. i guess that is sufficient enough.

WOOOW no way. Bad idea.
First, yes, everything you should have between OUT and ADJ pins is 3 ohms of resistance. Period. (or 3.33, if you can find one, or similar).

Second! Don't try LED as a test load. EVER. LED are designed to be nice glowing at 20~50 mA (depending). And by pushing 400mA through it, you'll gave it burned out in 1 second.
Test load is always 4x 1n400x diodes and one resistor of 1 ohm in series. That should have similar voltage drop of real laser diode. Current measuring is done by measuring voltage on the 1 ohm resistor, because of Ohm's law, it directly translates to current running through 'diode'.

Good luck with your build!

BTW ..... you can easily calculate the resistor for the current that you want, for a circuit based on LM317, using the formula 1.25/A=ohm ..... as example, 1.25/0.3 (300mA) = 4.16ohm

Or the inverse, if you want to know what mA give you a deretmined resistor, 1.25/R (in ohm) ..... example, 1.25/3,3 (3,3 ohm is a common value) = 0.378 (or 378mA)

And so on ..... and if you cannot find the exact resistor for the exact current that you want, you can always use 2 or more in parallel, until you obtain the value that you want ..... for caclulate the value of paralleled resistors, if the resistors are all equals, just divide the value for the number of resistors, like, 3 resistors of 15 ohm in parallel, give you 5 ohm ..... for different values, use the formula 1/((1/R1)+(1/R2)+(1/R3)) and so on ..... example (again ) a resistor of 15 ohm in parallel with a resistor of 4.7 ohm give you 1/((1/15)+(1/4.7)) = 3.58 ohm (approximating the last decimals).

Just remember that the same mA that you set, are also passing through the resistor, so you need to use a resistor that can hold the relative power (usually, you need to use AT LEAST half watt resistor, for currents over 100mA)

HIMNL9, I think I already wrote the formula for 317, but nice to have all the resistor formulas there, OP will need to use them very often if he will do more of electronics in future.

BTW, did you order your laser diode and module housing?

Eudaimonium said:

HIMNL9, I think I already wrote the formula for 317, but nice to have all the resistor formulas there, OP will need to use them very often if he will do more of electronics in future.

BTW, did you order your laser diode and module housing?

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Not yet, i suppose i'll order the 20x, and then switch out for 3 ohm resistor..as for the module, yeah i havea bunch from DX that i bought a long time ago.

creanzworld17 said:

Not yet, i suppose i'll order the 20x, and then switch out for 3 ohm resistor..as for the module, yeah i havea bunch from DX that i bought a long time ago.

Click to expand...

Do you know how to install /press it a diode into a housing? It can be tricky without right parts.
Go to youtube and punch in : how to make violet burning laser
Video you are searching for is by styropyro
Yeah I know, what does a violet laser have to do with our red ?
Well, in the middle of the vid, there is a nice explanation how to use back end of module and a vice to securely and nicely install a diode. You should do the same with your red one.

Also, don't forget to discharge the capacitor before connecting your laser diode! It could kill it! Just touch cap's pins with something metal, to short it out.