I would like to first state that I do not really know anything about circuit design- I am very much a beginner.
That being said, I am working on a project where I am using a laser to play music. I have the audio source (my iPod) going through an audio transformer (do not know the specifications, the circuit was given to me by my professor). I am powering the circuit with 4.5V and I have two LEDs that absorb excess voltage. The laser I am using is a 650nm 5mW laser. I measured the current through the laser diode and got 14mA. (I would like to add that I have tested this and at 4.5V, the laser is at its brightest and I have run it for over two hours, but I need a very robust circuit that can last forever essentially).
For some reason, the laser diodes keep burning out and I do not know why. I have done research and I found that a heat sink would help and so would a constant current source.
I want to operate the laser at the highest power without burning it out, so how do I do this? And when they say use a 'constant current source' what does that actually mean? When I look them up, I either find really large power sources where the lowest they go is 1A (I need 14mA). Or I find these small components that clearly need something else to them (like the LM317). What would you suggest for my problem?
Also, because the laser is transmitting the audio signal, the voltage fluctuates ever so slightly to create the signal- will this affect the solution?