Laser communication with photoresistor

Hi Everyone,
I been doing lots of googling but I guess nothing is really clear to me.
I wish to have a laser that send a pulse to a photoresistor.
How can I have the arduino to listen to a pulse? Pulsein() only works for the digital pins so that is out of the question apparently.

Thanks
Sean D

Just wire LDR to digital pin. OTOH, analog pin also works as digital.

SeanD:
Pulsein() only works for the digital pins so that is out of the question apparently.

Pulsein() watches for time between start and end edges of a pulse, nothing about amplitude. How does using a digital pin exclude that?

Hi guys,
If I connect my PhotoResistor to a digital pin and use PulseIn(), then wouldn't that always be HIGH?

Only when the light is on the photoresistor does current flow.
You do plan to modulate the laser?

If you are using pulseIn() the modulation should be as square-wave, PWM-like as you can get. If you swing the being-modulated beam across a wall, you should see dots and dashes.

Hi guys,
Thanks for the helpful info.
Any idea on how to get this laser to work?

What do I need to drop the voltage down to 3v and current at around 30ma?

I got 1 bag of these, gave away 4 and sent for another bag. Bag of 10 5mW red laser modules that run find on 5V for US$4.60 with free shipping to the US and probably other places too.

http://dx.com/p/12mm-5mw-red-laser-diode-modules-black-dc-4-5v-165078

12mm 5mW Red Laser Diode Modules - Black (DC 4.5V)

Model 6972
Quantity 10
Color Black
Material Plastic + iron
Specification Power: 5mW; Working voltage: 4.5V; Working current: 20mA; Working range: 1000 meters; Color BIN; Red
Features Mini and compact design
Application For DIY project
Packing List 10 x Laser module (8cm-cable)

Just be aware that photo resistors react slowly. They have a certain time from they have been exposed to light to they are back to their "dark resistance".
A photo transistor would probably be a better solution in your case.

EDIT:

This might be interessting:

Try to google "Arduino laser modem" that should give you something to go with.

Thanks guys! I will give those laser a try and will look into the laser modem.

Just got the lasers, 16 days from order.
You want phototransistors, they have those in quantity at the same place as the lasers. Look in Electronics for DIY.