How to controll a laser pointer from a microcontroller

[Conscripted]

Good afternoon all,

I'm in the design phase of a new project. I need to connect a laser to a microcontroller and I'm not sure what the best approach is. I intend to use a cheap off the shelf laser. I suspect that the laser may draw to much power to be powered by the microcontroller itself. Anyone have any experience with this?

Thanks
Conscripted

[SmAsH]

If you use a cheap laser could you not just use the battery that came with it and put a transistor where the switch normally is? Yes, a laser would draw to much current

[Soeren]

Hi,

I need to connect a laser to a microcontroller and I'm not sure what the best approach is. I intend to use a cheap off the shelf laser. I suspect that the laser may draw to much power to be powered by the microcontroller itself. Anyone have any experience with this?

A simple NPN transistor and two resistors will do, if the LASER can live off the same voltage as the controller. If it's a standard 3-cell pointer, a diode like 1N400x inline will drop a 5V line to around 4.35V, which should be just right for a 3-cell.

Do you need a schematic for this?

[nottoooily]

Be careful with the super-cheap laser pointers. I've found that the laser itself has about the same operating life as the batteries. Maybe I just got a bad batch, but it could be endemic!

[Conscripted]

Do you need a schematic for this?

A schematic would be great thanks

[Razor Concepts]

Replace LED and resistor with laser:

[Soeren]

Hi,

Replace LED and R1 with LASER and diode, in case of a 5V supply.
Make R2 somewhere around 3k3 to 4k7.

[Hawaii00000]

I just thought I'd tag this on while we're talking about it. I tried this one with a spare transitor and a cheap laser, but I didn't work completely. It was on constantly (even when it wasn't supposed to be) but it got brighter when power was applied to the transisor. Suggestions?

[Soeren]

Hi,

It was on constantly (even when it wasn't supposed to be) but it got brighter when power was applied to the transisor. Suggestions?

You clearly didn't drive the transistor from a CMOS output, so it didn't shut off the transistor fully.
If you just used a switch, a push button or a functional equivalent which didn't drive the base low, put a resistor (say 10k) from the base to the emitter/ground.

[amando96]

I like using these bad boys:
http://www.datasheetcatalog.org/datasheet/fairchild/4N35.pdf

they are easy to use, and a laser malfunction won't damage your micro!
It's also a good idea to use these with serial port/USB diy projects, your ports will be safe from little errors that could damage them...

[Soeren]

Hi,

they are easy to use, and a laser malfunction won't damage your micro!
It's also a good idea to use these with serial port/USB diy projects, your ports will be safe from little errors that could damage them...

A transistor (in OC configuration) won't backflow a malfunction either. It's a waste of money using opto-couplers here.

[Admin]

Not what you wanted to know, but still fun to watch

http://www.societyofrobots.com/robotforum/index.php?topic=4887.0

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