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My task it to design a product that will remotely monitor patients at a residential care home for the elderly. I will be using devices sourced from the SK Pang website that are compatible with the Arduino Uno board. I have decided in particular to research devices that use infrared technology, such as PIR sensors, Infrared rangefinders, infrared thermometer, optical dust sensor and infrared cameras. I have found all of these devices except for an infrared camera on the SK Pang website. It is not uncommon for the elderly to suffer from mental illness; they can become a danger to themselves and to other people. In this case they need to be kept under constant supervision; it would not be wise to allow a mental health patient free to roam the hallways. To combat this, my design concept is based on the ability to detect human presence, in particular detecting if someone has entered or exited a room. It could also be used to detect if someone is walking in the hallways or if a patient has gotten out of bed. Even though this concept is designed to be used in a medical environment, it serves more of a security purpose, rather than a medical one, and could potentially decrease some accidents associated with elderly mentally ill patients.

I will be researching Passive Infrared (PIR) sensors, and their current applications in security, medical and baby monitoring systems. The sensor will only detect an object that emits heat and that moves across the sensors field of vision. Once this happens the device will trip and send a pulse to the Arduino. I have chosen this sensor because it is the most widely used device in motion detecting applications, such as; In security Systems, PIR sensors are used as motion detection devices.  They are either placed in the corner of a room to detect intruders or near the doors of a building to turn on security lights. Some security cameras have these sensors to indicate when the camera should start recording. In Medical Monitoring systems, PIR sensors are used as motion detectors, fall detectors and can also detect if someone is entering or leaving a room. In baby monitoring systems, PIR sensors are used as motion detectors, to alert the parents if their child is awake. PIR sensors can also be used to turn on lights when motion is detected, or to open automatic doors.

The Hanse SE-10 PIR sensor only requires one data pin coming from the Arduino, so in theory one Arduino could support up to 20 sensors. This would require setting all pins to digital input. For the PIR to work it requires a 10Kohm resistor and connections to 3 pins, ground, power and alarm (See Wiring diagram for PIR sensor image) . The PIR requires 5-12 supply voltage in order to operate; fortunately the Arduino can supply 5v to the PIR from the pin labelled 5v. When the PIR device detects motion, the alarm pin is pulled low; this will need to be known in order to program the Arduino to know when the device has tripped. It has an effective range of about 3 to 7 meters, the average height of a ceiling in a modern building is 3 metres, and some older buildings can have wildly varying ceiling heights. The minimum angle for the devices field of vision is from 100, to less than 180 degrees.  Using the average height of a ceiling with the angle of the devices field of vision, we can calculate that we would require 1 device placed every 7.2 meters (3 x tan(50) = 3.58)  in order to cover a hallway or a large room. In the equation the value 3 represents the height of the sensor from the floor in meteres, and the value 50 represents the angle of the devices field of vision in degrees, divided by 2. The resulting value must be multiplied by 2 to get the diameter of the cone of vision.

The device could be placed above the door, so it can detect when someone enters or leaves the patients room. This is particularly useful for patients who suffer from mental illness and should not leave their rooms unattended. For patients that need assistance in getting out of bed, a sensor can be placed so the beam runs parallel to the bed, that way if the patient is to fall out of bed then the sensor will be tripped, thus alerting the nurse. Two devices could be attached to a wall, one placed at ankle height and another at waist height. This is to detect if a patient has fallen over, if this happens the floor detector will trip, but the waist height sensor will not. An alert can then be sent to the nursesí station. On the occasion that the sensor trips, and it has alerted the nursesí station. The alert will inform the nurse which PIR sensor has tripped and where it is located. The interface at the nursesí station could keep a record of all the times when a sensor has tripped, and possibly a map of all the sensors locations.

There are some problems with PIR sensors, such as objects that emit large amounts of infrared radiation, much like car headlights, can cause false alarms. So it would be best not to place the sensor where car headlights could be seen by it. Domestic animals such as cats and dogs can also cause false alarms, usually this is taken into account by ignoring anything on the floor, yet it is highly unlikely to find domestic animals in a care home. It is also recommended not to place the sensor near air vents or heating elements as they will heat the sensor above the ambient room temperature and could cause a false alarm. 


References:

(2011, June 8). Did It Move? Detecting Motion with PIR + Arduino. Retrieved from http://bildr.org/2011/06/pir_arduino/

Margolis, M. (2011). Arduino Cookbook. Retrieved from https://www.inkling.com/read/arduino-cookbook-michael-margolis-2nd/chapter-6/recipe-6-3
<p class="MsoNormal" style="text-align: left;">(2013). PIR Motion Sensor. Retrieved from <a href="http://www.skpang.co.uk/catalog/pir-motion-sensor-p-796.html">http://www.skpang.co.uk/catalog/pir-motion-sensor-p-796.html</a><o:p></o:p></p><p class="MsoNormal" style="text-align: left;">(2013, December 3). Wikipedia: Passive Infrared Sensor. Retrieved from <a href="http://en.wikipedia.org/wiki/Passive_infrared_sensor">http://en.wikipedia.org/wiki/Passive_infrared_sensor</a></p>""



download     2013-12-04 16:51     21.24 KB

PIR sensor





download     2013-12-04 12:54     16.01 KB

Wiring diagram for PIR sensor