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Problems with DDL driver - current regulation

ArRaY

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Hey everyone, I´am new to the forums and this is my first post.
Just for information, I´am 16 years old and i´am from Germany.

Some time ago, i became interested in lasers, and i started lurking around in this forum,
and in a german one. However, i did not dare to ask my questions in the german one,
because every second one, who is new to lasers, and who is asking a question there gets killed by postings regarding safety.
(I care much about Safety)


I read about the 16x dvd burner diodes, and thought that that would be an easy way to obtain a great, strong red laser.
I purchased some burners, and some lm317 for the driver.

After i got alle the components that i needed, (I´am new to electronics, so that was like everything :-D(Breadboard,resistors,...))
I wired it up on a breadboard. To test the circuit, i chose to try an led. scince i had it lying around, i took a 100 ohm resistor to test.
That should leave me with 12,5 mA, right?(1,25/100) I power the circuit with a 9V battery. So i wondered why the led was at full brightness and tried a 5k resistor. Again, full brightness. I left the resistor away, and again. Then i thought ADJ and Vout should have 1.25V difference. 0,0V says my DMM. I have no idea what could be wrong, and thus i´am asking you to look at my circuit if there is something obviously wrong.Thats what i think. But i don´t see it :-D

I hope someone here sees my mistake

Thanks in advance, ArRaY
 

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OMG WHAT ARE YOU DOING?! LASERS ARE NOT TOYS!!!!

;D ;D ;D ;D ;D

No, it's cool. Welcome to the forum.

The picture is very big, so it hard to see what's going on, but it looks like the wire from the capacitor goes to the wrong pin on the LM317. Move it to the pin to the left.
 
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FireMyLaser said:
OMG WHAT ARE YOU DOING?! LASERS ARE NOT TOYS!!!!

;D ;D ;D ;D ;D

No, it's cool. Welcome to the forum.

The picture is very big, so it hard to see what's going on, but it looks like the wire from the capacitor goes to the wrong pin on the LM317. Move it to the pin to the left.
;D ;D ;D ;D
 

ArRaY

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;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

I know. To be honest, i didn´t dare to hook up a diode to test, scince i have no glasses at the moment.

you sure? which one? the 10µF or the 100µF one?
My 317 is from ON-Semi, pinconfig is :
1 2 3
ADJ Vout Vin
 

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Yes, try it.

I mean the 100µF cap. Right now the wire goes to the middle (2) pin.
 

ArRaY

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the cap is the output cap.
i dont think it has to be connected to the input pin, thus having a direct connection to the + 9v, as it is supposed to be parallel to the LD...(tried it. led just lights up like is is directly connected to battery. which it then is, if you look at the board)

:'( so what else could be wrong?
 
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Did I get the pinning right in the picture?
1 2 3
ADJ Vout Vin
CIMG22521-1-1-1.jpg


Do what the red arrow does.

Check for shorts in the green circle.

The voltage between pin 1 and 2 should be 1.25V and the current through the circuit 12.5mA.
 

ArRaY

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ah i see :-D
i mixed up left with right :-D
shame on me^^

yes, pinning is right.

hm. voltage between 1 and 2 is 0.6v ??
There are no shorts in the green circle, but you can´t see that in the picture.

anyway, thanks for helping
 
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What' the current? If it's too low, then get a new 9V battery and check the voltage between pin 1 and 2 again.
It has to be 1.25V or something's wrong!
 

ArRaY

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yaaay! took a new battery and the voltage is 1.24!!
Thanks a lot!!
 

ArRaY

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Du bist nicht im ernst auch Deutscher oder? ;)

However, i still don´t know where the difference is between placing the diode between adj and Vout, scince both are connected together....
 
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Was? Mein deutsch ist slecht.

They are not connected together (directly), there's the difference. ::)
 

ArRaY

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I asked you if you are a german, in german ;)

Now it works, but ain´t i connecting the diode between adj and gnd?
I always thought i had to connect it between out and gnd...
 
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"I asked you if you are a german, in german"
Obviously not! ;D Welcome to Sweden.


As strange as it sounds, yes, you'll connect the diode between adj and gnd with this circuit. ;)
 

ArRaY

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At first i thought you fooled me, because you wrote english, just for saying your from my on country. ;D

Strange. In all these circuit diagrams, there was always the load connected between out and gnd.
Even in the datasheet. But no problem, thanks for pointing that out.

ArRaY
 




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