laser security system

hi,
i want build a security system using laser beam. circuit design is very easy, but i block in sensor part and laser torch part. any one please help me to find proper sensor and laser torch. this system should work all 24 hours and 365 days. so it's durability is very important.please help me.

another final year project? Google for LDRs (light detecting resistors), Op-amps in comparator mode. A 2-buck chinese laser pen is good enough for demonstration.

thank for reply. this is not a final year project.this is industrial work. that's why i need a good laser source and good LDR for this project. i buy a LDR & chinese laser pointer from local market. but both are not working properly. if you know some place to buy this laser source & LDR please reply me. than you.

both are not working properly, as how not properly? An LDR just changes its resistance with changes of light intensity, and it exhibits a recognizable range of resistance if a red light from your laser is pointed at it.
Chinese models are okay, you just change the batteries with good ones and as for the electronics, buy an LM358 and check out its datasheet for applications for comparator mode.
Hope this helps.

thank for reply. the meaning of "both are not working properly" is when time goes, laser pointer & LDR not work properly. I'm going to use regulated main supply for system & when emergency, use batteries. when i give regulated suitable voltage to chinese laser pointer it was burned. problem in LDR is ,i think it not suitable for power of laser. so it showing high resistance in all times.(after 3 months). so i must find good laser source and suitable photodiode or phototransistor or LDR for that. i laser beam must go 40 feet without reducing its intensity and using sensor i want to get a pulse when laser beam cut. when i searching google i found this
**broken link removed**
broblem is i don't know it's power info for purpose & it cant use continually.
thank you.

thank for reply. the meaning of "both are not working properly" is when time goes, laser pointer & LDR not work properly. I'm going to use regulated main supply for system & when emergency, use batteries. when i give regulated suitable voltage to chinese laser pointer it was burned. problem in LDR is ,i think it not suitable for power of laser. so it showing high resistance in all times.(after 3 months). so i must find good laser source and suitable photodiode or phototransistor or LDR for that. i laser beam must go 40 feet without reducing its intensity and using sensor i want to get a pulse when laser beam cut. when i searching google i found this
**broken link removed**
broblem is i don't know it's power info for purpose & it cant use continually.
thank you.

of course it burns, that laser diode only withstands small values of current. How much is your power supply when you jam it to the laser diode terminals? Use a resistor in series, usually 1kΩ works fine for most off-the-wall dc power supply.

Buy a phototransistor then if you can't find a good LDR. You can google for those projects with those keywords, LDRs, photodiodes, laser diodes and op-amps. I'm not googling them for you, no offense. That module thingy is not loading properly in my netbook, I can't view it.

thank you. i will try it.
thank you very much for reply me.