Home Automation and PIR(Passive Infrared Sensor)

Khyati Kiyawat
Aug 24, 2017 · 4 min read

HALLOWEEN IS COMING up faster than you think: time to dust off the gravestones and the zombie lawn decorations! This year you may want to add a little something extra to give the trick-or-treaters a bit of a thrill.

"Home automation" is a category that can span really simple to extremely complex tasks depending on who you ask. It's easy to get overwhelmed by jargon and devices and standards.
Before the invention of mobile phones nobody has thought we could contact anybody anywhere anytime but the technology made communication easier and now mobile phones are everyones’ heartbeat. The point of consideration is; any new technology or invention is just a dream until it reaches masses. In just a few years, the Internet has started to add connectivity to everything from home audio to even garage doors. Known as the ‘Internet of Things’ this growth in technology is now leading to affordable and easy-to-use systems, apps, and hardware for automating your entire home.

A smart home cares for you

Home automation involves automatic controlling of all electrical or electronic devices in homes or even remotely through wireless communication. The sensors detects light, motion, temperature and other sensing elements, and then send that data to the main controlling devices.

Just imagine how carefree our life would be if everything could be controlled by a single switch or app in our smart phones. You put your feet into your room and there is already someone or something giving you a motherly feel, a sensor which senses your arrival and switches on lights, fan and music system for you. If you are still wondering what it is then remember the switching on of lights in washrooms of shopping malls.Occupancy sensor is the cool tool.

Sensors based on different technologies like infrared, microwave and ultrasonic are being included in the wide world of IoT and home automation. Occupancy sensors are typically used to save energy, provide automatic control, and comply with building codes.
Various applications of occupancy sensor found out till now include :

•Turning on street lights on less dense roads when any vehicle passes
• Acting as virtual security guard in lawns of your house
• Turning on home appliances when the owner foots into house
• Wide and wise use in robotics
These are very few but most popular areas, more such innovative applications are in their dormant stages.

Let’s explore the tiny PIR sensors :

PIR sensors work on the principle of sensing Passive Infrared Radiation emitted by objects or individuals using pyroelectric sensor. When a warm body like a human or animal passes by, it first intercepts one half of the PIR sensor, which causes a positive differential change between the two halves. When the warm body leaves the sensing area, the reverse happens, whereby the sensor generates a negative differential change. These change pulses are what is detected. Area of detection of these sensors varies from 5m to as high as 60m. PIR sensors are compatible with all interfaces like Arduino, Raspberry pi, etc.

Let’s dig deeper into the working and configuration of PIR sensor;
The lens protecting the sensor converges all the infrared rays falling on it to the pyroelectric sensor window. The optics behind the structure of Fresnel lens can be exploited to increase the range of detection.

Working of PIR sensor

The converged rays fall onto a RE002B sensor which has two windows which sense any input which is no less than 10 microwatts and detects any spatial temperature variations. Output of these windows serve as input to JFET whose output voltage is sent to an amplifier for further processing of the signal. The signal processing in the sensor circuit include passing the analog signal to a comparator to determine when to trigger it, then to multistage amplifier to get the final digital output.
We can even set the trigerring pulse width by changing values of resistor and capacitor connected to 3-5 pins of BISS0001 chip. Sensitivity of the sensor can also be increased.
Futher, your code determines how you can meet your requirements in the best possible ways.

Some more captivating and enthralling IoT projects are:
• Home automation using Bluetooth module
• Home automation using Zigbee, WiFi, GSM module

Control from anywhere it’s in your hand

Wi-Charge
• Amazon Echo
• Adobe Home Security kit
• Belkin Wemo Wifi Switches

Further References

http://www.instructables.com/id/PIR-Motion-Sensor-Tutorial
https://circuitdigest.com/

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