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Inside a $1 radar motion sensor

10maurycy10.github.io

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Re: Inside a $1 radar motion sensor

#61

Post by simondanerd »

lpcvoid wrote: post #53
perlgeek wrote: post #52

Earlier quoted context omitted.

Non-ionizing radio waves are generally safe for humans. The only mechanism besides ionization that could harm humans is through the transfer of lots of power into the human body (think soldiers keeping themselves warm by stepping in front of a radar emitter). So let's try to do a ballpark estimate of how much that could matter. I haven't found (from a quick search) any data regarding the transmission power, but the d…

>soldiers keeping themselves warm by stepping in front of a radar emitter Holy, did people actually do this? A quick search yielded no results. Not sure if thankful or not.

Works, it's a weird feeling, speaking from experience. HF antennas can give some respectable burns too.

But the effects are debated and not entirely scientific: https://www.reddit.com/r/army/comments/13r6hod/i_keep_being_...

Re: Inside a $1 radar motion sensor

#62

Post by mianos »

stavros wrote: post #37
mianos wrote: post #31

Earlier quoted context omitted.

Wrong, most of these radars are 24Ghz and specifically designed to detect body micro movements. They specifically give both human 'occupancy' and dynamic ranging information. I wrote low level drivers for the ESP32 for all the ones I could buy and have tested all of them. The only one that does not try to give a human occupancy position is the car speed sensor. The ld2450 can track three people at once. https://githu…

This sounds very interesting, how do your drivers work? I'd love to try them out, but there's no documentation. I've made a sensor board with various sensors, I could really use some occupancy detection improvements on the LD2450B.

All the boards provided by HiLink have an on board MCU and offer a serial protocol of some sort. I wrote a finite state machine based decoder for each them from the basic info on some documents,random example code and the textual description of the protocol from the aliexpress page. They are all wrapped in an outer state machine that provides entry and exit triggers. If you can read C++ the code is nothing fancy.

I have another more complete project for just the 2450 in another repo for the esp-idf with wifi provisioning and publishes presence to mqtt. I have 3 of these around the house.

Re: Inside a $1 radar motion sensor

#63

Post by LoganDark »

stavros wrote: post #39
LoganDark wrote: post #34

Earlier quoted context omitted.

I think it's also survivorship bias. All the people who tell you they're vegan being vegan does not mean that all the people who are vegan will tell you they're vegan, just like all the people who won the lottery probably having bought lots of tickets does not mean that buying lots of tickets will win you the lottery.

That's what I meant, maybe I used the wrong bias name.

Confirmation bias typically refers to accepting very little evidence or rejecting disproofs. Survivorship bias is the one where you forget to account for the non-survivors of a particular selection criteria.

Re: Inside a $1 radar motion sensor

#64

Post by moffkalast »

lpcvoid wrote: post #53
perlgeek wrote: post #52

Earlier quoted context omitted.

Non-ionizing radio waves are generally safe for humans. The only mechanism besides ionization that could harm humans is through the transfer of lots of power into the human body (think soldiers keeping themselves warm by stepping in front of a radar emitter). So let's try to do a ballpark estimate of how much that could matter. I haven't found (from a quick search) any data regarding the transmission power, but the d…

>soldiers keeping themselves warm by stepping in front of a radar emitter Holy, did people actually do this? A quick search yielded no results. Not sure if thankful or not.

Weren't microwave ovens invented because someone's chocolate melted in their pocket while operating a radio transmitter? Maybe it's just a lady godiva story since it seems weird that the person wouldn't feel overly hot as well, but maybe.

Re: Inside a $1 radar motion sensor

#65

Post by moffkalast »

Avamander wrote: post #43
t0mas88 wrote: post #20

Earlier quoted context omitted.

I have these all around the house, but not in the bedrooms. I use weight sensors to detect that someone is in bed and traditional PIR for motion in bedrooms. Probably overly careful, but I didn't want to point a radar at my sleeping kids (and myself) for 12 hours per day. Similar for the WiFi access point upstairs, it's only in the hallway and not at maximum power.

> Probably overly careful, but I didn't want to point a radar at my sleeping kids (and myself) for 12 hours per day. While I understand the sentiment. It's very very unlikely to be dangerous and there are plenty of other environmental dangers. The biggest being the sun. But the most common man-made ones are probably auditory. Like toys and TVs being too loud or high-frequency sounds blasted from speakers in malls or…

Yeah on one hand you have people afraid of wifi and simultaneously sending their kids to play all day outside in UV index 11 without a hat or sunscreen. Things that are "natural" being inherently safe and anything technological literally death itself.

Re: Inside a $1 radar motion sensor

#66

Post by stavros »

mianos wrote: post #62
stavros wrote: post #37

Earlier quoted context omitted.

This sounds very interesting, how do your drivers work? I'd love to try them out, but there's no documentation. I've made a sensor board with various sensors, I could really use some occupancy detection improvements on the LD2450B.

All the boards provided by HiLink have an on board MCU and offer a serial protocol of some sort. I wrote a finite state machine based decoder for each them from the basic info on some documents,random example code and the textual description of the protocol from the aliexpress page. They are all wrapped in an outer state machine that provides entry and exit triggers. If you can read C++ the code is nothing fancy. I h…

That's great, I'll have a look, thank you!

Re: Inside a $1 radar motion sensor

#67

Post by hippich »

aeonik wrote: post #48
hippich wrote: post #45

Almost not related, but reminded me about recent RC hack I was working on. I have an driveway alarm from mighty mule, which uses 433Mhz radio powered by two AA batteries to communicate signal from the coil sensor detection sitting next to the driveway to the base station in the house using OOK modulation. The stock PCB antenna was not very good at the distance I had it to work with, so I started experimenting with ex…

I need to see a picture, but fyi some of components of an antenna are "electrically" disconnected, but still play a role, wave guides being one example. Also note, if you are just receiving signals you have more freedom to experiment. Antenna tuning matters a lot more when transmitting (especially at larger powers). (Not implying that it doesn't matter with reception)

Just to clarify - I changed transmitters antenna.

Re: Inside a $1 radar motion sensor

#68

Post by LoganDark »

TeMPOraL wrote: post #57
stavros wrote: post #39

Earlier quoted context omitted.

That's what I meant, maybe I used the wrong bias name.

I know this under "selection bias", so now we have three contenders. Still, I'm not sure if it's a big factor. You likely know who is vegan in your circles, because veganism is unusual enough to be a good topic for gossip, you can easily see it when sharing a meal with someone, and it's also something you'd like to know when inviting people over, if you want to be a good host. So I think a more relevant estimate woul…

I believe survivorship bias is a specific type of selection bias.

Re: Inside a $1 radar motion sensor

#69

Post by utensil4778 »

transpute wrote: post #2

Through-wall 2.4Ghz Wi-Fi CSI radar can be done with $20 ESP32 boards, https://github.com/Marsrocky/Awesome-WiFi-CSI-Sensing & https://www.cnx-software.com/2022/08/08/esp-wifi-csi-detects... > Espressif claims it can also capture subtle movements caused by small movements such as breathing and chewing of people or animals in a static environment.. works with all ESP32 series microcontrollers including ESP32, ESP32-S2…

The gesture recognition sounds incredibly interesting. I work with vision based band tracking, and performance really isn't good enough for my application.

I wonder what kind of resolution you can reasonably achieve? Is it good enough to detect finger pose?

Aside: is there a way around IEEE paywall? I'd really love to read some of these papers

Re: Inside a $1 radar motion sensor

#70

Post by marcosdumay »

stavros wrote: post #24
tstrimple wrote: post #16

Earlier quoted context omitted.

Strangely enough I've heard far more people make this "joke" than actual vegans speaking up. Even when living in LA.

The issue with this joke is that it's 100% confirmation bias. You know that all the vegans tell you they're vegan because you don't know about the ones that didn't.

There are people that I discovered were vegans when discussing what to eat. And there are people that loudly announced they'd become vegans without any context.

The later group used to be larger, but I don't remember anybody doing that recently.

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