Problem with this Laser diode circuit

[tPS]

I have dismantled an old DVDRW drive and taken a 4-pin laser diode from it.

After connecting it to two 2A batteries (red with positive, and blue with negative), the light beam is diverging, and the brightness is even dimmer than another laser diode that I got from a presentation pen.

Also, the it became hot within a few seconds that I can even smell the smell of the solder melting. Is there something that I should modify in the circuit to make it work properly?
(Sorry if I am asking in the wrong place)

 

[Baluncore]

Also, the it became hot within a few seconds that I can even smell the smell of the solder melting. Is there something that I should modify in the circuit to make it work properly?

Maybe you need a series resistor to limit the laser diode current.
What wavelength light do you expect from that laser diode?

 

[tPS]

Maybe you need a series resistor to limit the laser diode current.
What wavelength light do you expect from that laser diode?

i think it is 660nm.
Current being too large would lower the "brightness" of the laser?

 

[Baluncore]

I expect the high current may have destroyed the laser diode as part of your learning exercise. But you may have been lucky. Light output is reduced as the temperature rises. When the diode cools it may recover.

Do not look into the beam. The diode may appear to be dim if seen from the side. Aim the laser diode at a white sheet of paper to scatter the light so you can see the colour without risk to your eyesight. An unknown laser diode may be an IR diode, invisible to you. Take great care.

You used two cells in series which could be between 2.4 and 3.3 V, depending on the chemistry of the battery. A red, 660 nm laser diode should have a forward voltage of about; 1240 / 660 nm = 1.87 V.

To limit current to say about 10 mA, with a 3.3 V supply, you will need a series resistor of about; ( 3.3 - 1.87 ) / 10 mA = 150 ohms. Anything near that will do for a quick test.

 

[alan123hk]

I sympathize with the damage to your laser diode.
First of all, please note that you must handle the laser diode with care, because even the very low laser light power emitted from the laser diode may harm your eyes.

After connecting it to two 2A batteries (red with positive, and blue with negative), the light beam is diverging, and the brightness is even dimmer than another laser diode that I got from a presentation pen

If you remove the laser diode from the DVDRW drive, but do not together with a properly installed collimating lens, of course the laser light will become divergent.

Also, the it became hot within a few seconds that I can even smell the smell of the solder melting. Is there something that I should modify in the circuit to make it work properly?

There are two basic units inside the laser diode, namely LD and PD. LD stands for laser diode and PD stands for photodiode. In order to control the correct laser power output, the driver uses negative feedback topology to control the current of the LD based on the output of the PD.

Obviously, if the feedback control circuit is damaged or disturbed, for example, the original shielding structure is removed, the PD will be incorrectly affected by ambient light, the loss of the shielding structure (including the collimating lens) will also cause the reduction of internal reflections, which in turn reduces the power received by the PD from the LD, etc., then the LD current will not be controlled, and the components of the circuit may be heated and burned.

https://www.twovolt.com/2016/08/23/laser-diode-driver-using-transistors/
https://www.teamwavelength.com/laser-diode-driver-basics/

 

[Rive]

...the brightness is even dimmer than another laser diode that I got from a presentation pen.

That's normal: they are different type. An optical drive does not need that much power as a pointer, but it needs precision.

 

[tPS]

Do not look into the beam. The diode may appear to be dim if seen from the side. Aim the laser diode at a white sheet of paper to scatter the light so you can see the colour without risk to your eyesight. An unknown laser diode may be an IR diode, invisible to you. Take great care.

I didnt look directly into the beam, I compare the brightness by aiming it onto the wall next to me, thanks for the concerning

You used two cells in series which could be between 2.4 and 3.3 V, depending on the chemistry of the battery. A red, 660 nm laser diode should have a forward voltage of about; 1240 / 660 nm = 1.87 V.

To limit current to say about 10 mA, with a 3.3 V supply, you will need a series resistor of about; ( 3.3 - 1.87 ) / 10 mA = 150 ohms. Anything near that will do for a quick test.

I don't have any resistor on hand, but I would definitely go buy some a few days later! Thank you!

 

[tPS]

There are two basic units inside the laser diode, namely LD and PD. LD stands for laser diode and PD stands for photodiode. In order to control the correct laser power output, the driver uses negative feedback topology to control the current of the LD based on the output of the PD.

Obviously, if the feedback control circuit is damaged or disturbed, for example, the original shielding structure is removed, the PD will be incorrectly affected by ambient light, the loss of the shielding structure (including the collimating lens) will also cause the reduction of internal reflections, which in turn reduces the power received by the PD from the LD, etc., then the LD current will not be controlled, and the components of the circuit may be heated and burned.

So if I leave out the PD pin, the laser diode would attempt to work on it's maximum power and burn itself?

 

[tPS]

That's normal: they are different type. An optical drive does not need that much power as a pointer, but it needs precision.

it was a rewritable drive so i assumed the power of it would be higher than the laser pointer