By: Saketh & Jishnu, 6C
By Jishnu and Saketh, 6C

This sample application could be used as the starting point to build a touch-enabled and motion-activated doorbell, which could then make sounds using a buzzer. It uses a Passive Infrared (PIR) sensor that will detect the presence of a human which would illuminate the LED and activate the alarm and capacitive sense buttons for a touch input.

This simple alarm can be used to detect the movement of human beings at a distance of 10-20 meters. It works both day and night and beeps shortly when there is a human movement through its detecting range. It is ideal to monitor the entry passages, stair case, corridors etc. It is highly useful to monitor the human movements in flats, multi storied buildings, schools, shops, industries etc. A relay can also be connected to activate lights, electric alarms etc. It can be used as a Personal alarm during journey to protect luggage.

It is an assembled unit with PIR sensor, signal amplifier, presets for adjusting sensitivity range, duration of output etc. There are three connecting pins for VCC, ground and output. It is marked on the module. It works off 5-12 volt DC and the output is positive to drive the transistor. In the standby mode, the sensor sets its sensitivity by using the ambient temperature around it and the surface on which it is fixed. When a human being passes across its detecting range, the passive infrared radiation (heat) from the body changes the sensitivity of the sensor and its output turns high. This output is used to drive the transistor to switch on the buzzer.