[HN Gopher] Using low-cost wireless sensors in the unlicensed bands
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       Using low-cost wireless sensors in the unlicensed bands
        
       Author : signa11
       Score  : 31 points
       Date   : 2023-02-10 07:17 UTC (1 days ago)
        
 (HTM) web link (lwn.net)
 (TXT) w3m dump (lwn.net)
        
       | VLM wrote:
       | This is "older" tech so the installed base is (was?) large.
       | 
       | In the past I found out if you use "level" in the format string
       | it will output signal strength type data that you can analyze. It
       | is not rocket surgery to store a DB row consisting of timestamp,
       | id, and signal strength of all RX'd packets, then make a
       | dashboard of how many unique IDs you hear over a ten minute
       | period or whatever.
       | 
       | My hope was to detect 70 cm ham radio band openings (tropo ducts
       | and the like) Wow did that never work. It was a good idea and fun
       | but did not work at all. I repurposed the hardware into something
       | else and moved on. Its possible that with different antennas or
       | longer term project or something, who knows. The software, as in
       | the article's link, worked fine however.
       | 
       | If you'd like to try another frustrating IoT experiment, try
       | monitoring all the tire pressure monitor systems that drive by
       | your house using roughly the same hardware and similar software.
       | IIRC I ran out of patience with that one. Sounded like fun after
       | I saw a YT video on the topic... The good news is each tire on
       | the road (by 2023 anyway) has a unique 32 bit ID, IIRC anyway,
       | the bad news is the range was scarcely better than "a car length"
       | away. If you've ever driven your car over the machine with the
       | hoses the DOT puts out to count cars along a road for planning
       | purposes, I thought I could replicate that kind of data by
       | sniffing and analyzing TPMS data, but the range is WAY too low
       | for the low repetition rate of the transmissions. I guess you
       | could just gather data wirelessly for years at a time, but ...
       | Maybe you could make parking meters really smart by listening for
       | the tires parked at the meter, or track super expensive private
       | parking, or an electric charger could pre-load the new user by
       | sniffing the new user's tire transmitters. Or my garage door
       | could automatically open if and only if my car is at the door.
       | However the transmission rate is too low for most door opener
       | level of patience.
        
         | hummus_bae wrote:
         | Dumb question, but do you have ID of your house on the chip?
         | You could at least have a high and low threshold for your house
         | and compare it to other houses.
        
       | timerol wrote:
       | The opening of this article is confusing. It contrasts relatively
       | expensive Zigbee and Z-Wave devices with cheap sensors emitting
       | radio signals in the unlicensed ISM bands. But Zigbee and Z-Wave
       | both operate in ISM bands, so the distinction isn't a difference.
       | 
       | It's more like the difference between building and hosting a
       | static website with Squarespace vs. AWS. One of them is more
       | expensive with more bells and whistles, but both accomplish
       | similar goals by communicating with the browser in similar ways.
        
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       (page generated 2023-02-11 23:00 UTC)