Motion Activated Switch for Alarm, Light or Water Sprinkler

The motion sensor switch circuit can automatically initiate a water sprinkler nevertheless you can easily put it to use as a motion sensor light switch or motion activated sensor also. Before you start the construction speak to your local electronics component supplier and procure a readymade box-type Passive Infrared (PIR) Motion Sensor product.
These units, stuffed in a modest enclosure with power input and relay output terminals are abundant.

In prototype, an unbranded (Built in China) PIR Motion sensor with the following features are widely-used.

Sensing Range:10Meter Maximum
Supply Voltage:12V DC, <500mA
Relay Output: Common(C),Normally Closed(N/C),Normally Opened(N/O)
Relay ON time: 15 Secs (Not variable)
pir motion sensor unit

Now install the PIR unit hanging from a three metre high mast (to deal with ten metre radius region) and hook up its supply and relay terminals to our completed and completely enclosed circuit, paying attention to precise polarity. A 4-core screened wire can be used for this purpose interconnection. Power the circuit from a regulated 12VDC adaptor/solar power box.

The moment the PIR module identify action of a organic figure its relay output toggles and the mosfet (T1) in the circuit is turned to on via resistor R1 and connected components. As as result, the EM relay at the output of T1 is triggered and the electric sprinkler becomes its supply from the relay (RLY1) contacts. This contacts (or spare contacts) can also be employed to switch on a high-power cautionary alarm.

Keep in mind that, here T1 is cabled as a small sized electronic timer. Even after the PIR relay is turned off, output relay (RLY1) remains to be in on state for a quick duration decided by the value of timing capacitor C2.

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