A motion sensor light switch is a great way of saving energy shortfall periods. A PIR sensor light switch will automatically detect when someone enters the room or any place where the motion sensor is set. Then, after a few minutes(adjusted by your desires) when no movement has been detected, the lights will then automatically be turned off. Although a motion sensor switch is indeed a big and important invention. In fact, you can install a motion sensor light switch much in the same way as you would a single pole light switch.
The circuit diagram of the motion sensor light switch is given below.
|3||Transistor||BC 547/BC548 or equivalent||1|
|6||PIR sensor||3.3 to 20V DC input||1|
|7||Bulb||AC bulb or DC bulb can be used||1|
|8||BCB||You can use it without PCB||1|
All living things (humans or animals), whose body temperature is more than 0 degrees Centigrade, emit the heat in form of infrared radiation through their body, also called thermal radiation. This Radiated energy is invisible to the human eye. These heat Signals can be detected by using a PIR sensor which is specially designed for such purpose.
This is a motion detector sensor that detects the movement of human beings and triggers its output to a High state (low or high). It operates in two modes low and high. The mode is selected by the jumper provided on the rear side of the PIR sensor PCB which is shown in the figure given below. If the sensor with an input voltage capability of 12V is not in your reach, use LM 7805/7806 regulator to control the 12v current if you give 12v current directly the sensor may be damaged.
Normal Mode: When the Passive infrared sensor detects motion it sets the output to High until the set time end, independent of the movements during the output HIGH time. This is a one-time triggering mode.
Re-Triggering Mode: When the PIR sensor detects motion, it sets the output to High until a set time becomes Low, but if it detects motion during its output High state 1, it again triggers the timer making it count from zero.
The Delay Time indicates how long the PIR sensor will keep the Output High (ON) as detecting motion.
For example, when motion has been detected, you could set this somewhere between a few seconds to a few minutes time period.