The automatic PIR motion sensor switch circuit will be able to quickly switch on a water sprinkler although it is possible to utilize it as a motion sensor light switch or motion activated security alarm as well. Before you start the building get in touch with your local electronics component seller and acquire a readymade box-type Passive Infrared (PIR) Motion Sensor device.
This kind of products, come in packed in a lightweight housing along with power input points and relay output terminals tend to be extensively on the market.
In my PIR motion sensor circuit prototype, an ordinary PIR Motion sensor having the listed features are recommended.
Detection Range:10Meter Maximum
Supply Input:12V DC, <500mA
Relay Output :Common(C),Normally Closed(N/C),Normally Opened(N/O)
Relay ON time: 15 Secs (Not Adjustable)
Pir motion sensor unit
At this moment set up the PIR module suspending from a 3 metre high mast (to insure 10 metre radius area) and hook up its supply and relay pins to your completed and encased circuit, paying attention to right polarity. A 4-core scanned cable works extremely well just for this inter-connection. Power the circuit through a 12VDC adaptor/solar power box.
At any time when the PIR module discovers motion of a living human body its relay output switches-on and the mosfet (T1) in the circuit is turned to on by way of resistor R1 and associated components. As as result, the EM relay at the output of T1 is triggered and also the electric sprinkler obtains its supply from the relay (RLY1) contacts. This contacts (or extra contacts) may additionally be applied to trigger a high-power warning security alarm.
You should be aware that, here T1 is rigged like a small electronic timer. Perhaps as soon as the PIR relay switched off, output relay (RLY1) continues to be in activated condition for a brief period determined by the value of timing capacitor C2.