laser alarm

2Shae

Hi,
Lately my brother keeps comming in my room while im gone to use my pc even though he has his own, he just wants to play w0w and keeps bringing down my god dam rank. i want to setup a laser alarm system like i seen on mythbusters.
basily a coulple of those cheap laser pointers and an alarm bell, but i cant figure out howto tell if someone walks infront of the reciever, howto i make a reciever. btw ive only started electronics so be as basic as possible
once i have made 2 of the revievers i will power on the 2 lasers with a couple of battries. the main tasks is to get the reciever made

Thomas_S_Hunterson

Eh password protect your computer...

To do it the mythbusters way, use the laser, and entirelly seperately, a Light Dependant Resistor + Transistor to activate a relay which will do whatever it is you want to do.

Here's a diagram
http://www.uoguelph.ca/~antoon/circ/actrelay.htm

2Shae

damnit i hate trying to make these things, i wish i could find a premade one. i suck at electronics

themole

Try maplin.
They could sell premade ones, or they might have a kit which you could assemble yourself.

But as already said, why not just chance your password?
Or lock your door?