plz help !!!

[harryd]

dude, i seriously cant thank you enough . u are like my idol right now. THANK YOU

i am using 2 x10 ohm( giving only 5 ohm in total ) as a fixed resistance... should i just change the 2x10 with one 27 ?

ok just going over the steps:
1- disconnect the dummy circuit
2- connect both wires together 3 times to discharge
3- connect the laser diode
4- set the resistance at( 1.25/30ma( the operating current)=41 ohm and we have a fixed 27 ohm so )41-27= 14 ohm. set the resistance at 14 ohm
5- connect the voltage supply and make it 9 v

**** the laser diode should emit red laser*****
6-then gradually decrease the resistance till it hits zero

 

[lasersbee]

NO.....
Always start at the lowest current and work your way up...

Use the Test Load to make sure the driver can give you the
Max and Min currents as I outlined above...
If your driver can do that... then.... and only then...

1) set your driver to minimum
2) disconnect power to your Driver
3) disconnect your Test Load
4) discharge the output capacitor
5) connect your Laser Diode to your Driver
6) put power on your driver
7) slowly increase the current until you get lasing..

BTW when you say you are using 2 x10 ohm resistors to give 5 ohms...
you need to tell us if you put them in parallel or series...
We can not see what you did... only you can see what you did..
You may think you have 5 Ohms when in fact you have 20 ohms
because you put them in series.... we just don't know... because
the small detail of series/parallel is missing... :undecided:


Jerry

 

[harryd]

According to your Data Sheet.... the Max output is 7mW at a Max
Current of 50mA... you will use pins #1 and #2 only...

If you build the LM317 driver and between the Adjust pin and output pin
of the LM317 you put only a 27 Ohm resistor is series with your 100 Ohm trimpot...

1) with the trimpot at Maximum resistance (the lowest current setting) the total
resistance will be ~127 Ohms..

1.25/127 Ohms = ~10mA

2) with the trimpot at minimum resistance (the highest current setting) the total
resistance will be ~27 Ohms..

1.25/27 Ohms = ~46mA

This is well in the range of your Laser Diode... Test it with your Test Load
across the 1 Ohm resistor with your DMM set to 200mV full scale.

Don't forget... your Laser Diode will only start to Lase at ~25mA as stated
in the Data Sheet..

Yes.... to discharge the output cap of your Laser Driver Just touch the wires
that connect to your Test Load together with NO POWER to the Driver.
That will discharge the capacitor... I would do this 3 times to be sure it is
discharged.


Jerry

when u said pins 1 and 2.... i think u meant 1 and 3 right ? and 1 is the negative and 3 is the positive right ?

 

[harryd]

oh nvm u were right. 1 and 2



bad news :S

i connected everything and i checked that the diode will see 30 ma then i discharged and everything and i connected the diode but it didn't work.

ofc if it is doesnt work this means it is burned right ?

 

[lasersbee]

when u said pins 1 and 2.... i think u meant 1 and 3 right ? and 1 is the negative and 3 is the positive right ?

NO.... (1) is the Positive and (2) is the Negative...
The info is clearly shown on the Spec Sheet....

BTW.... LD = Laser Diode... PD = Photo Diode


Jerry

 

[harryd]

yes yes i did that.. dont worry but still it didnt work.

i honestly dont know what is wrong. i connected the tes load , measure the mv acroos the 1 ohm resistor and it was at first 26mv. i discharged and everything then i connected the laser diode but nothing worked, i tried to increase the current slowly, still nothing.


and how i can tell if the laser diode is burned