running a laser diode without drive

[wmashda]

I am wondering could i run a laser diode with a drive, could i use resistors instead? if so has anyone got a wiring diagram?

Thanks,
Graham Russell.

 

[ElektroFreak]

No. You definitely need a driver. Resistors by themselves are insufficient. If you search the forum for "LM317 driver" or "DDL driver" you'll find information on an extremely simple driver you can build for next to nothing from RadioShack parts..

This image (creator unknown) contains the schematic:

 

[Cyparagon]

As long as the voltage source itself is regulated, resistors will be sufficient. So If you're using batteries, a driver is a better idea, but it will still work with resistors.

 

[LiveRock]

If you use resistors, you will have to note the followings:

1. Power and heat lost thru resistors.
2. As battery voltage drop, so does the current
3. As LD gets heated up, internal resistance also changes, thereby current also changes.
In other words, there is no regulation of current.

So, use a safe value for the resistor to cater for all the scenarios.

 

[Tw15t3r]

Which will mean that you cannot maximise the power output of your laser or risk it being fried since you can't run it near max current because you do not have a stable current source.