The SparkFun TTL Laser is a easy to use red laser that can be controlled by a microcontroller (e.g. Arduino) or used as a stand-alone laser pointer. Lasers can be great for many things; everything from a cat toy to a simple optical communication system using a photocell for a receiver.
The red laser has a wavelength close to 650nm and a power range of 0.45-0.8mW. This is not enough power to burn a hole in the wall, but it is enough NOT to shine into someones eyes.
On the TTL Laser, there is a polarized 4-pin connector with these connections:
red wire - 5-12VDC input
black wire - GND
green wire - 10k pull-down (aka, GND)
white wire - active low TTL input (3.3V or 5V logic)
The basic operation of the Laser module is very simple. If all you want to do is turn the laser ON and leave it ON, you first power the module by connecting a 5-12VDC power source to the red wire and GND to the black wire. Then you connect the green and white wires together or just connect the white wire to GND while leaving the green wire unconnected. This will turn the laser ON.
If you want to control the laser, you can connect the white wire to a TTL output on a microcontroller (along with power and ground). The green wire can be left unconnected. Here is how you control the TTL Laser with an Arduino:
Then all you need to do is load the very basic "Blink" sketch. Your laser will begin blinking every second, in opposition to the LED on pin 13.