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Hello LPF. New here please help /w Driver

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whatsupadrian

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I been lurking for a while and finally decided to jump on this and build myself a laser. I have a limited amount of electronics experience, i know  how to solder and ohms law, furthest i got in school was Boolean algebra.

Yesterday I ordered a LPC-815 Diode and Aixiz Module from Jake21

Today I am working on building a driver. Now I'v read the DDL Driver Schematic several times and I see that the pot is just used to adjust the current from the LM317. Since the pot is just an adjustable resistor, I plan to substitute it with a 3ohm resistor. Multisim says my current would then be 416.818mA.

Can one of you laser experts look over this schematic and tell me if I'm on the right track? I'm open to ALL suggestions. My goal is to get close to 420mA OR whatever is a good power for this diode(you guys know best).

Schematic Link.... (3 DOTs)
img13DOTimageshackDOTus/img13/79/69507949DOTjpg

I plan on putting this thing in a flashlight and using probably 2 CR123A, But still open to suggestions.
 





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whatsupadrian

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Thank you. I try to answer my own questions before I ask.

Does my circuit seem like a winner with this particular LD?
 
pseudolobster

pseudolobster

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Yep, sounds good!

Just be sure you use at least a half watt resistor, preferably a 1W... I dunno the math, but the resistor will be dissipating at least half a watt at that current. Also might be a good idea to get a heatsink that will fit your flashlight so the diode doesn't overheat. Also I'm not sure what the AH on the end of the LM317 part number means, but if it's a nonstandard packaging like surface mount etc, you'll likely want to provide some heatsinking for the regulator as well.
 
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whatsupadrian

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The AH was added my Multisim. I have the standard LM317T from radio shack that's being used. Also I am going to be using 3x 1ohm 1/4 watt resistors in series. Do you think 3ohm at 3/4W is enough?

I do plan on making a pro lookin flashlight /w heatsink once funds become available.
 
pseudolobster

pseudolobster

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If I'm not mistaken, 3x 1/4W resistors in series will still have a power rating of 1/4W... You might want to change that to a single 3ohm 1W resistor, or maybe IDK, 3x 10ohm 1/4W resistors in parallel, which would give you 375mA... It's erring on the safe side, though it won't give you the power output you might have been hoping for.

PS: Lasersbee, your link doesn't work either! it's: http://img13.imageshack.us/img13/79/69507949.jpg ... no "www"
 
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whatsupadrian

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Ok well i went to radioshack and bouch a 500 pack of resistors, because it was the only assortment that had 1 ohm resistors in it. I bought it and it contained 290 resistors in it. 10 1 ohm resistors were missing and this package seemed unopened! JUST MY LUCK!! so i was actually thinking.... I can use 3 x 22 ohm and 1 5ohm in parallel to get 2.973 ohm which on my circuit on multisim calculates out to 420.606mA at the diode. PLEASE PLEASE PLEASE double check this for me or correct me if I'm wrong.

Actually dont have a 5 ohm resistor but i have 3 15 ohm ones. so thats 6 resistors all in parallel. Anyone have a better idea without using a POT.
 
Warske

Warske

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Your math checks. The 15 ohm resistors are only dissipating 0.1 watt each, so that works too. Nothing better than that with what you have.

When you put it all together, if you can't bring the power up slowly while monitoring laser current, it would be a really, really good idea to put together a dummy load in place of the laser and test it with that first. There is info about that in the forum, but you are obviously able to figure out your own circuit for a load. I tested one of the LPC-815 diodes and got a voltage across it of 2.47 v at 200 mA, 3.07v at 420 mA.

Also, as others have mentioned elsewhere, make sure the cap is discharged before hooking it across the laser diode.

And welcome...
 
sk8er4514

sk8er4514

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whatsupadrian said:
Ok well i went to radioshack and bouch a 500 pack of resistors, because it was the only assortment that had 1 ohm resistors in it. I bought it and it contained 290 resistors in it. 10 1 ohm resistors were missing and this package seemed unopened! JUST MY LUCK!! so i was actually thinking.... I can use 3 x 22 ohm and 1 5ohm in parallel to get 2.973 ohm which on my circuit on multisim calculates out to 420.606mA at the diode. PLEASE PLEASE PLEASE double check this for me or correct me if I'm wrong.

Actually dont have a 5 ohm resistor but i have 3 15 ohm ones. so thats 6 resistors all in parallel. Anyone have a better idea without using a POT.
Click to expand...
I have a bunch of 1 ohm resistors, see attached picture. I wouldn't mind sending you a few if you'd like to make an order on my site to pay for shipping / have a reason to send you them :) can be something cheap, [link=http://hightechdealz.com/index.php?main_page=product_info&cPath=1&products_id=11]Aixiz module[/link] ? or maybe some [link=http://hightechdealz.com/index.php?main_page=product_info&cPath=4&products_id=16]empty PHR803T sleds[/link] :)

good luck with your build.

thanks,
Kendall
 

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whatsupadrian

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Ok well i failed my first and second driver attempts. Both failed because I used a 63watt hakko with a huge chisel tip at 3AM.

Ill post some pics of my fail
adrianDOThardbrakingDOTcom/laser/
 
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whatsupadrian

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ok i ended up making a new driver from scratch and did a much better job on it. I used 3x 1 ohm resistors in series across the LM317. How do i go about testing this to make sure its where I need it to be, I don't have my LD in yet.

Here are some picture.
adrianDOThardbrakingDOTcom/laser/first_good_driver/

Thank you all for your great help!
 
Warske

Warske

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Warske said:
...it would be a really, really good idea to put together a dummy load in place of the laser and test it with that first.  There is info about that in the forum, but you are obviously able to figure out your own circuit for a load.  I tested one of the LPC-815 diodes and got a voltage across it of 2.47 v at 200 mA, 3.07v at 420 mA.
Click to expand...
whatsupadrian said:
How do i go about testing this to make sure its where I need it to be, I don't have my LD in yet.
Click to expand...
Do you have access to a volt meter and 6 vdc for power?
 
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whatsupadrian

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Im afraid my DMM wont read the current even if i made a test load. Im pretty sure i have a AC to DC converter sitting around thats outputs 6vDC.
 
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whatsupadrian

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driver.JPG

driver%20(2).JPG

driver%20(3).JPG

driver%20(4).JPG
 
Warske

Warske

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whatsupadrian said:
Im afraid my DMM wont read the current even if i made a test load. Im pretty sure i have a AC to DC converter sitting around thats outputs 6vDC.
Click to expand...
That's all you need.

So,

[highlight]r = v / i = 3.07 / .420 = 7.3 ohms

P = v * i = 3.07 * .420 = 1.3 watts[/highlight]

Use your bag of resistors to make up a 7.3 ohm test load which is good for 1.3 watts or more.

Power it up and read the voltage across the test load. If your circuit works, it should read 3.07 volts.

It should read the same 3.07 volts even if the power supply voltage varies somewhat.
 
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