I would like to make a device that will detect when a beam is broken. What can i use for this?
The beam must span across about 2 metres.
The beam and lightsource must be invisible.
The device will be based outdoors so must be able to contend with sunlight.
Any suggestions please? Thanks.
What will be braeking teh beam - I guess I'm really asking how long the bean will be broken for.
My initial thoughts would be pulsed infra red into a shielded IR reciever (probably a short tube for shielding).
Sunlight has lots of IR in it (well lots of lots of frequencies of light), so you need to shield the sensor from direct sunlight and the pulsing will enable you to detect your light in high ambient light conditions.
Mike
I want to create a device for scaring off foxes. The emission source plus the sensor can be put inside tubes so they will be suitable shielded from the sun.
A cheap laserpointer i a tube on one side and a LDR (light dependent resistor) in a tube on the other side. If the tubes are long (deep) enough changes in ambient light will have a minimal effect compared to the laser.
This will work best with a powersupply, as the laser will exhaust batteries to fast.
I'm not too happy about that solution. I have two pet cats that will also be wandering around in the area and I don't want them to get a laser in their eyes.
Here is a pair of IR devices that are probably suitable:
Also, this project might give you some ideas:
http://www.instructables.com/id/IR_light_trip_sensor/
Mike
Thanks, but I have come across this cheap product that will fit the bill nicely....