Broken Beam Laser Fence

[cassiel]

Hi,

I found alot of threads on this subject, but none really solid enough to tackle.

Anyway, so I got my hands on a couple of Laser pointers and would like to know what type of receiver you guys would suggest. Perhaps a circuit too. I have no idea at what frequency they work so I don't think a modulated receiver will work.

Will a typical IR receiver pick up the red laser beam? The beam is focus-able and claimed to reach 600m. I need a range of about 40m, easy enough...

Any ideas on building a circuit?

Thanks and merry Xmas!
Martin

 

[justDIY]

a regular ir photodiode / transistor will receive a red laser just fine, if you need better noise rejection, you could modulate your laser using a 555 circuit (or microcontroller) and then use a typical IR receiver ic (diode + amp + filter + demodulator in a nice little package)

oh, on the cheap, a red led will work too, either as a photodiode or a photovoltaic ... either way will need an amplifier or a sensitive input

 

[cassiel]

The pointers I got only has two supply leads coming out. I don't know if modulating the supply to it will be a good idea. Can you guys give me typical components to use? I have no idea where to even start selecting components.

I haven'r worked with opto-electronics before.

 

[Sceadwian]

You should be able to modulate them just fine, though I don't know at what frequency. Only way to find out is to try it. If it turns out to be bad for the lasers then maybe use an LCD shutter instead.

 

[justDIY]

if they're cheap pointers, they'll have the bare minimum of regulation circuitry (usually just a feedback diode and pass transistor) modulation should be as easy as turning the power on and off, modulate at 38-40kHz for the typical IR receivers.

 

[chemelec]

There is a fairly Simple Laser Alarm circuit on my website.

Its not modulated, but it works quite well. I also sell a 2N5777 that will detect the Visable Red Light.

Belated Merry Christmas
****************************************

Hi,

I found alot of threads on this subject, but none really solid enough to tackle.

Anyway, so I got my hands on a couple of Laser pointers and would like to know what type of receiver you guys would suggest. Perhaps a circuit too. I have no idea at what frequency they work so I don't think a modulated receiver will work.

Will a typical IR receiver pick up the red laser beam? The beam is focus-able and claimed to reach 600m. I need a range of about 40m, easy enough...

Any ideas on building a circuit?

Thanks and merry Xmas!
Martin