Instructables
video DIY Theft alarm
السلام عليكم HI!
I am going to show how to make your own theft alarm.
This laser-triggered theft alarm is useful for many purposes. This theft alarm also includes a 555 timer IC monostable circuit for persistence of the trigger.
This alarm costs only 2$ for all the stuff. Because of this reason, it is considered one of the cheapest alarms in the world.
You can use some mirrors to make the laser reflect and increase its protection.
You will need:
BC547 transistor
NE555 timer
1kΩ resistor
10kΩ resistor
1μf capacitor
Breadboard (optional)
2 LDRs
5mW laser pointer

I have also included the schematic for easy understanding.
Note: the parts may vary according to the newer version and all the unnamed resistors are of value 1 kΩ
iburrow10 months ago
well done guys this does look straight forward and will definitely serve a very worthwhile purpose. Please, could you sketch out a schematic so I can get my simple mind around where which bits go? keep it up.
fahadshihab (author)  iburrow10 months ago
Thanks for the good feedback... also I have included the schematic in my instructable. I hope, the schematic will be helpful for you...
mwallis110 months ago
agree with iburrow for those of us who have little or no knowledge this looks like you can just stick all the parts in anywhere. a schematic would be helpful more in depth written instructions maybe? looks good though