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Comment by zild3d | Hacker News Reader

I had a professor that did his thesis on a 10 year coin cell powered wireless sensor. Although it was a transmit only protocol. Pretty well understood area - send less data, put the system to sleep for as long as feasible.

http://www.firner.com/research.html

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Transmit-only mechanisms are definitely the best way to go to reach the extreme minimum in low power levels. The problem with transmit-only systems is that they are difficult to use in most real-world situations. Once you have deployed a transmit-only sensor, you are stuck with the configuration that was hard-coded into it. There is no way to change how often you want the sensor to report, how and when it should trigger, and any other parameters and requirements that may change as the project develops - encryption keys being one example.

Definitely, although the inability to receive can be considered a security feature for some applications. Wireless hackers have to go through a receiver :)

The EnOcean protocol is a good example of this. Their sensors don't use batteries at all, instead opting to charge a capacitor from small PV panels or peltier generators.

https://www.enocean.com/en/technology/energy-harvesting-wire...

https://www.enocean.com/en/technology/energy-harvesting/

This is well suited to stuff like occupancy sensors in buildings. Time resolution isn't as small as an always-powered system could be, but if your use case for the data is "Turn off the lights if we haven't seen anyone move for 30 minutes" then it doesn't much matter if you transmit every 5 minutes instead of every 5 seconds.

Transmit only for the high power active radio is often a great way to save power, so long as you have an alternative data path to send information to the device to change settings or do firmware updates. For example, see the Omni-ID Power 415 active RFID tag which transmits up to 400 m distance with its active radio every few seconds for 5+ years of battery life but also has a passive 900 MHz RFID interface that's bidirectional for changing settings or doing firmware updates.

http://www.rfidjournal.com/articles/view?11873

You don't have to sacrifice configurability to get the power benefits. Send the data transmit-only, but every few days have a receive window.

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