user8423: Firstly, I must apologise as I'm a complete noob but the Arduino kits / lego pieces are fantastic and I can't stop tinkering.  Unfortunatley my knowledge does not match my passion.
I picked up a laser from Amazon: FamilyMall(TM) KY-008 Laser Transmitter Module 650nm 5V Diode For Arduino AVR PIC.
I'm wondering what the middle pin is good for and if I can somehow manage to detect and respond to the beam being broken? 
Thanks for looking. :)

user8476: Without a data sheet or the device on hand not sure what the middle pin is used for.  On the topic of detecting a broken beam the item you purchased is purely an emitter, in order to detect the beam being broken there are two main ways, using a photodetector on the "opposite end" of the beam but this means having wires trailing the same path as the laser beam, alternatively you could mount a mirror where the beam lands and reflect it back to a photodetector mounted close to the laser diode.  You would them use the arduino to detect the state of the photodetector.

8423: <p>Firstly, I must apologise as I'm a complete noob but the Arduino kits / lego pieces are fantastic and I can't stop tinkering.  Unfortunatley my knowledge does not match my passion.</p>

<p>I picked up a laser from <a href="http://www.amazon.co.uk/FamilyMall-KY-008-Transmitter-Module-Arduino/dp/B00KYHL7HO" rel="nofollow">Amazon: FamilyMall(TM) KY-008 Laser Transmitter Module 650nm 5V Diode For Arduino AVR PIC</a>.</p>

<p>I'm wondering what the middle pin is good for and if I can somehow manage to detect and respond to the beam being broken? </p>

<p>Thanks for looking. :)</p>
 8476: <p>Without a data sheet or the device on hand not sure what the middle pin is used for.  On the topic of detecting a broken beam the item you purchased is purely an emitter, in order to detect the beam being broken there are two main ways, using a photodetector on the "opposite end" of the beam but this means having wires trailing the same path as the laser beam, alternatively you could mount a mirror where the beam lands and reflect it back to a photodetector mounted close to the laser diode.  You would them use the arduino to detect the state of the photodetector.</p>
