Safety Wristband for Active Security Network

This paper describes a development that has been carried out by the Autolog-UCLM research group in partnership with local Industry as a result of an employee falling ill during work in a huge assembly workshop, and not being detected until the end of a 12 hours shift. The proposed system can trigger rescue operations and be connected to active data networks. It can be used in enclosed environments such as factories or hospitals. The system requires the specified area to be provided with a complete wireless infrastructure running passively in the background. The nodes of this infrastructure are fitted with alarm signals (acoustical and optical sirens) and located in places where they can be seen by the security cameras (to provide redundancy). Each person in this environment is then required to wear a wristband-like bracelet for the duration of their stay/shift; which communicates with the wireless network via ZigBee protocol. The wristband is fitted with a simple and low-cost movement detector (accelerometer) and a buzzer/led. As it is very unusual for a healthy person not to move the hands, the wristband will start to buzz and the led will flash if it does not detect movement for a number of seconds (adjustable, typically half a minute). The person can then cancel the alarm just by moving the hand or by tapping the bracelet (single tap for cancelling). If the alarm is not cancelled (in ten seconds) or the person voluntarily taps the bracelet (double tap for activating) when no alarm is already set, the wristband will transmit an alarm signal through the ZigBee network. The alarm will be displayed at a computer in the security booth (screen and sound) with the identity of the zone and of the wristband; and the first node in the network to detect the wristband with the alarm (zone node) will turn on its alarm siren. The security personnel will thus be notified in real time, but the other persons in the area will also see the alarm, as will the security cameras. At regular short intervals, the wristbands transmit beacon signals; so that both the concerned person and the security personnel will be notified if a wristband losses radio contact. This system is very cheap, as the wristband does not need GPS units etc. being only active within the specified enclosure. In the case that longer distances are required, it would only be necessary to incorporate a GPRS/SMS system to one of the nodes in this local network.