Hi everyone, I designed a circuit to connect one laser on it. This is the circuit:

As you can see the output is 3 V what is needed for the laser. Can I connect it directly? What do I have to change if I want to connect 2 lasers?

 

The laser (as well as the LED) requires a current supply. And with your circuitry, you can disable the laser.
You can attach my model collection.
It has customizable models of lasers. According to the laser diode data I will help you to set up these models.
Reference:
http://bordodynov.ltwiki.org/

 

What current does the laser take, as it will drop voltage across the 1 ohm resistor, and waste power, i would remove it, and use a Constant Current mode.

 

What current does the laser take, as it will drop voltage across the 1 ohm resistor, and waste power, i would remove it, and use a Constant Current mode.

It would take 250 mA. But I thought laser diode takes the current it needs.

 

Ok, best to look at the data sheet for your laser, if it says fixed voltage ok, remove the 1 ohm resistor..

 

See

 

Do you have a link to the data sheet for the LASER you have, just as an example 3v 5mW 650nm Red Dot Laser Diode Module. The link provides the LASER power so if I have a 3 Volt 5 mW module I can figure the required current at 3 volts applied. If I want to add another module of the same type I will need twice the current from my supply source. Modules like the one I linked to include current limiting for their LASER diode so only knowing the module voltage is important. You want a supply capable of delivering the maximum load current and then some, like a 20% overhead.

Ron