Need some help.

Hi there,

this is my first time trying to build a red burning laser using the laser diode from my old DVD-RW drive. i saw kipkap's video but i know laser diode are extremely sensitive when used without a driver. i successfully extracted the diode out and manage to put it into a laser module that i got off some hardware store.

now i'm trying to build the driver so that my laser diode wouldnt die. i got all the necessary parts. I don't know what's the highest mA i could acheive without damaging my laser diode.

i need some help regarding the circuitry.

i couldn't identify the connection for the 100 ohm pot, lm317. and i am not too sure if the polarity of the LN4001 diode matters. please i need some help with that.


So this is my 100 ohm potentiometer. there are a total of 3 connector. 1 at the top, 2 at the bottom. which is the 1, 2 and 3 if i'm using daedal's driver tutorial circuit.


same for my lm317, which is the in,out and adj?


which is the positive and negative side of it?(that's if it matters)

Click on the pictures to view it in a larger size.

a link to daedal's DIY driver circuit
http://laserpointerforums.com/attachments/f42/11702-diy-homemade-laser-diode-driver-ld_driver_schematic.jpg

thanks in advance. appreciate all you guys' help

This shows it much better. By rog8811
On the Pot., one of the bottom ones, (or you can tie them together) will run to pin 3 of the LM317, and the top one goes to the resistor

Thanks alot, Greenmechanic.

since now i know the pin configuration of the pot,lm317 and diode, can i use 1 of the 0.25W 3.9 ohm resistor instead of 2 10ohm resistor in parallel?


if i am using daedal's DIY driver, the battery source mentioned is 6V, which is equilvalent to 4 x AA batteries. any idea what kind of battery i could use? by any chance, lithium ion batteries? i know of a place near my area that sells those batteries. any specific model?

lastly, how much current can i supply to my laser diode without it frying itself?
the resistors i have are 3.9 ohm resistor.

let's say if i supply 125mA of current. so it is 1.25 divide 125 = 0.01
0.01 x 1000 = 10 ohms
so i shld use a 10 ohm resistor if i want a current of 125mA?

so if my maths aint wrong,
a 3.9 ohm resistor will make my current to the laser diode a whopping 320mA. wouldn't it fry the diode?

It depend on the actual LD you are using...
BTW... your math is correct...
You could use your 3.9 Ohm resistor or 2 in series to lower
the max current to 160ma Max...

Don't forget the Resistor current calculation is with the pot set
to zero resistance... The Pot only reduces the Max current..

What I would suggest is to use a Test Load to set your Driver's
current or if you were using a 10 turn 100 Ohm TrimPot you can
set the Pot to the Max resistance (min current) and very slowly
turn the pot until you got the LD lasing...
Be carefull not to exceed the Max allowable current for your
particular LD..

Jerry

hi jerry,
thanks for your input.

for the LD, i'm using an old DVD-RW burner LD, any idea what's the amount of current will produce a more sustainable diode life? i sure dont want the dead laser diode count to go up

i managed to make the driver using a proto-board. the laser is shown, but not bright like what i see on videos on youtube. i was powering the circuit with a 9V square battery, yet to test with 4 AAs. i tune my pot to the lowest and it was shown 1.6 - 1.7 ohms at lowest, my resistor was 5.2ohm.i measure the pot and resistor using my electronic ammeter.

so if i do my math again, it shld b 7ohm at max

7/ 1000 = 0.007
1.25 / 0.007 = 178mA

the only thing was i notice from the beam is that, the dot isnt a dot, but rather like rectangle. was it the lens that cause it to be rectangle or other factors?

i saw a video on youtube, a guy had a total of 400mA going into the LD and manage to create some intense burning power.
http://www.youtube.com/watch?v=nmNq8p1OQZQ

will putting a 400mA instantly fry my LD?

It is really hard to tell.. you are using 'some old dvd writer diode', which doesnt really tell much about what diode came out of that, or about what it is or should be albe to handle in terms of output power or input current.

Without that information your guess is as good as mine - it might work okay at 200 or 300 mA, or die on the spot.

Then again, if you happen to kill the diode, you can replace it with a known model like one from a <$10 LPC sled. Many members have experience with those and could advise you on current vs lifetime considerations.

GrooveFlare said:

i was powering the circuit with a 9V square battery, yet to test with 4 AAs. i tune my pot to the lowest and it was shown 1.6 - 1.7 ohms at lowest, my resistor was 5.2ohm.i measure the pot and resistor using my electronic ammeter.

so if i do my math again, it shld b 7ohm at max

7/ 1000 = 0.007
1.25 / 0.007 = 178mA

the only thing was i notice from the beam is that, the dot isnt a dot, but rather like rectangle. was it the lens that cause it to be rectangle or other factors?

i saw a video on youtube, a guy had a total of 400mA going into the LD and manage to create some intense burning power.
YouTube - DVD Burning laser-homemade

will putting a 400mA instantly fry my LD?

Click to expand...

A 9V battery is not a very good power source, (low mAh at higher current) The best bet would to buy a few 18650's and a charger.
Using 2, this will produce 7.2-8.4V, plenty to run a DDL using a LOC or LCC. and they have 2400mAh each.

What type of lens are you using? You have to have a very short focal length lens to properly focus the diode. The LD on its own (without separate lens) will be squarish and very unfocused.

The higher power you run the LD, the shorter the life will be. But IMHO, 320mA is not pushing it hard at all. You should have a good life time if you keep it under 350mA. (if it's a LOC, which is probably is)
You do however, need very good heat-sinking at this current.

As to the video on Youtube of the 400mA LD, check out this one I made at 510mA, ( LCC,very well heat-sink'ed and fan cooled)
YouTube - Fun with 510mA LCC.WMV

Great advice and info from GreenM & Jerry too^^^--good luck and WELCOME

Greenmechanic said:

A 9V battery is not a very good power source, (low mAh at higher current) The best bet would to buy a few 18650's and a charger.
Using 2, this will produce 7.2-8.4V, plenty to run a DDL using a LOC or LCC. and they have 2400mAh each.

What type of lens are you using? You have to have a very short focal length lens to properly focus the diode. The LD on its own (without separate lens) will be squarish and very unfocused.

The higher power you run the LD, the shorter the life will be. But IMHO, 320mA is not pushing it hard at all. You should have a good life time if you keep it under 350mA. (if it's a LOC, which is probably is)
You do however, need very good heat-sinking at this current.

As to the video on Youtube of the 400mA LD, check out this one I made at 510mA, ( LCC,very well heat-sink'ed and fan cooled)
YouTube - Fun with 510mA LCC.WMV

Click to expand...

thanks again, greenmechanic.
the video of the 510mA was pretty sweet.

the lens that i am using, i'm not too sure of it myself too. i got the laser module of an electronic hardware store available locally. i removed the diode and just used the lens.

as for the power source, i'm considering to switch to 4 x AA batteries before considering the 18650s.

will test it out when i get some new parts. hopefully i will be able to post pictures of my laser.

you need to press fit the diode in an aixiz module and what speed is the DVD-RW.... 16x, 18x, 20x?

stuart

yep, i did press the diode into the module. it has fit nicely on the module.
the speed of the DVD-RW that i used is 20x

GrooveFlare said:

yep, i did press the diode into the module. it has fit nicely on the module.
the speed of the DVD-RW that i used is 20x

Click to expand...

im assuming that it is an LOC (Long Open Can) diode then... these can be pushed to 420mA happily, but different diodes vary, so be cautious.

stuart

thank stuart.

np

stuart

i've manage to make the driver. it works and the beam is definately stronger. i'm using just 3ohms of resistance. making it roughly 416mA.

i notice that my beam at its max focus, it produces a line instead of a dot. the lens that i'm using is a dot lens. any idea why the best focal point produces a line instead of a dot?

a picture of it would better answer your question.

stuart