laser+arduino

[1mpar]

Hi,

I got a project where I'm thinking about using 5 laser pointers turned on/off by arduino. I'm having a problem that I can't turn it on using the digital pins. When I connect the laser (that has 300mW) directly to the 3.3V and GND it works, but when I send the same voltage using one digital pin (connecting only the pin and the GND to the pointer) it doens't work.
Does anyone knows what´s the problem?
Is there any other way of connection that it would work?

Thanks,
Henrique

 

[Rafa]

You're going to kill the arduino doing that.

Do this:

Connect the 10K resistor to the output pin of your arduino and Vout to whereever you want your output. I guess it will be a laser module this case.

 

[Rafa]

Look, these 2 are easyer to understand

The problme is that the arduino cant give too much current directly from the pin, so you have to put a transistor that can handle more current than the arduino.

 

[1mpar]

Hi, rafa

thanks for answering.

is this figure below right?

about the transistor, how can I specify the right one?
and can I use these values for the resistor?

PS: sorry, I'm not good in electronics...

 

[Rafa]

Make this:

 

[HIMNL9]

^ Just be sure that the PSU of the Arduino can give the current required from the laser module , AND that the laser module works with 5V (green ones are usually 3V or 3.3V, not 5V)

 

[1mpar]

^ Just be sure that the PSU of the Arduino can give the current required from the laser module , AND that the laser module works with 5V (green ones are usually 3V or 3.3V, not 5V)

How can I calculate the ammount of current the laser needs?

It works with 3V, 2 AAA batteries.

 

[HIMNL9]

^ then don't use the 5V (it's a green, right ?) ..... use the 3.3V, or an external 3V PSU .....

You can measure the current placing a DMM on 2A scale in serie with the batteries.

 

[Rafa]

HIMNL9 is right. I don't think arduino can give.... maybe 1.5A out of the 3.3V output.

You may want to use an LM317 to regulate the current.

Make this instead:

EDIT: Crap that is not correct. You should connect the 390R resistor to ground.