This tutorial from deba168 on Instructables shows you how to build a diy home security system:
In this project I will discuss how you can make a cheap wireless home security system.Though during starting of this project the main objective was only for security alarm but later I found this device can be used to solve several problems.These are the few practical problems which I have faced in the past :
1. Few years ago my friend’s new bike was stolen from the parking premises of our apartment.
2. Mangoes are stolen from our garden.
3. One of my friend always worried for his new born baby when sleeping on a bed but no one is there to monitor him.
By modifying few things in my device you can solve all these problems very easily.
My device uses a PIR motion sensor to detect the human motion and this information is transmitted without wire by using a RF transmitter-receiver module to give some sort of alert.I choose a RF module for wire less communication because compared to the existing wireless systems like blue tooth,XBee or WiFi ,it is user friendly and very cheap.You can get it from eBay @ less than $ 2.
You could use IR, but that has a limited range and can only work within a line of sight of the receiver.But using the cheap RF module we can communicate within the range of around 100m.
At the end I will give you few tips to reduce the power consumption.
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