Had an interesting request from an OT today. The scenario is a client with epilepsy who also has a learning disability and an impaired level of mobility (poor balance/stability). The requirement is a sensor at the bottom of the stairs and another at entrance to the bedroom so the parents are alerted when he is moving about upstairs (or about to go upstairs) so they can supervise – but that only alerts when the client is moving as opposed to anyone else. This implies a proximity system based on something the client wears and would trigger the sensor within (say) a few feet.
Ideas I’ve been mulling over are:
A simple infra red transmitter that pulses every few seconds to conserve battery life. This might work (perhaps in the form of a device clipped to clothing) but the IR could bounce around and trigger the sensor from a greater distance, or if focused (or obscured by the client), could miss the sensor altogether.
A 433mhz band transmitter of the type used for simple remote control switch applications. But not sure the range could be attenuated to the point it would only work at a few feet.
Passive RFID tag – the range of operation is way too short. i.e. the tag has got to be very close to the sensor as there is no internal power.
Active RFID tag/active reader – the readers tend to be very expensive and the range will end up too great.
Any other ideas welcome!