Why did the Laser diode got damaged ?

[nvd]

Laser diode

I was using LASER diode for the serial communication between two computers using the standard serial port. Since the power supply was +12V, I used 7805 regulator to drop the voltage to +5 volts. Then I used series resistors to drop additional voltage so that the voltage across the LASER diode should be +3V when it drew 30mA of current. It worked at lower baud rates say 110 but as I used rate of 9600, it startd to give less light. I thought it due to the duty factor as specified by the data pulses but LASER got dim and did not give any intense beam anymore.
Can I revive it? Why did it get damaged? Was it 7805 as I didn't use a capacitor at its output (+5V).

 

[IanP]

Re: Laser diode

Instead of resistors to drop voltage from 5V to 3 use 3 silicone diodes in series (≈2V voltage drop, 1N4002 or similar) .. and try again.
This will not limit the pulse current as the resistors do ..

 

[nand_gates]

Re: Laser diode

Hi nvd,
Can you please upload the circuit diagram of ur serial communication using
Laser diode here??

 

[vicky]

Re: Laser diode

HI!
Dear u can also use the bridge rectifier for the best results. it will also protect your circuitry and sensors. Also try to change your current limmitations and then check the results.

 

[eda4you]

Re: Laser diode

Please upload your schematic! Debugging will be more easier for us.

Also look for the load regulation of your 5V supply. Maybe this limits your bandwidth.