Re: wireless sensors, and battery life: time synch

"Bruce Boyes" <lego-robotics@xxxxxxxxxx> wrote in message
news:6.2.1.2.2.20050602112705.030107a8@xxxxxxxxxxxxxxxxxxxx
> Part of the battery life issue, as you allude, is not listening all the
> time. To make this happen, nodes have to share a common and precise time
> base. Then they just have to wake up at the allotted time. This is harder
> than it sounds, and is the subject of standards such as IEEE1588. We plan
> to experiment with this with our Zigbee nodes, since the power savings can
> be really significant.

maybe it should be done in the same way as rfid id cards
let's say when controler wants to wake the sensor up
it sends the signal and the sensor (all sensors)
1. powers itself using this signal
2. do the job

rfid id cards are not powered and they are not in listen mode
in fact rfid cards are tataly dead when they have no signal from sender

i know the range of rfid is pretty short
but maybe just the idea can be used

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