It is simple burglar alarm using ir sensor .
when any thing come near ir led & photo diode ,ir ray reflect and relay on then buzzer active
Step 1: You Need to Make This Project
IR proximity sensor
single channel relay module (5v)
old mobile phone battery or any other battery( 3.7v)
cabinet box ( I use soap case )
Step 2: Connection
keep ir module in digital mode.
connect ir module out to relay in pin
vcc to vcc & gnd to gnd .
now connect buzzer to relay & gnd
now supply with battery via bread board
Step 3: Fit to a Cabinet
fit all components in a small case.I use small soap case
now test it & enjoy