11 ms·
Inside a $1 radar motion sensor
- m3047 2y agoWiener functions. I love 'em. An analog application too, top secret in WW II. Now also used in handset to eNodeB comms.
- threeme3 2y agoMore details https://github.com/jdesbonnet/RCWL-0516 https://github.com/jdesbonnet/RCWL-0516
- fennecfoxy 2y agoDon't like these cheap sensors most of the time since most can't tell between a moving person and a fan rotating or curtain moving in a breeze. They are configurable to some degree but seems like not enough. I'm sure there are more expensive options but they're more locked down/limited as well.
- transpute 2y agoThrough-wall 2.4Ghz Wi-Fi CSI radar can be done with $20 ESP32 boards, https://github.com/Marsrocky/Awesome-WiFi-CSI-Sensing https://github.com/Marsrocky/Awesome-WiFi-CSI-Sensing & https://www.cnx-software.com/2022/08/08/esp-wifi-csi-detects-humans-with-wifi-signals-only-no-sensor-needed/ https://www.cnx-software.com/2022/08/08/esp-wifi-csi-detects... > Espressif claims it can also capture subtle movements caused by small movements such as breathing and chewing of people or animals in a static environment.. works with all ESP32 series microcontrollers including ESP32, ESP32-S2, and ESP32-C3, and does not require any changes to the hardware 2024 AI/NPU laptops with Wi-Fi 7 from Intel and Qualcomm can combine RF radar and on-device inference to identify human activity. Related: DIY Radio Telescope: Building a Camera That Can See WiFi (2019) https://www.youtube.com/watch?v=g3LT_b6K0Mc https://www.youtube.com/watch?v=g3LT_b6K0Mc Wi-Fi devices set to become object sensors by 2024 via IEEE 802.11bf standard (2021), https://news.ycombinator.com/item?id=40458766 https://news.ycombinator.com/item?id=40458766 How automotive radar measures the velocity of objects (2024) https://news.ycombinator.com/item?id=40768959 https://news.ycombinator.com/item?id=40768959 How Wi-Fi sensing of movement became usable (2024) https://www.technologyreview.com/2024/02/27/1088154/wifi-sensing-tracking-movements/ https://www.technologyreview.com/2024/02/27/1088154/wifi-sen...
- throwup238 2y ago> chewing of people or animals The ESP32 can detect the difference between a cannibal and a vegan? That's impressive.
- lopis 2y agoHow can you tell someone is a vegan? Don't worry, this 1$ radar motion sensor can tell you.
- silisili 2y agoI think you could go cheaper. A sound detection sensor is a bit cheaper, and it just needs to detect the word 'vegan.'
- tstrimple 2y agoStrangely enough I've heard far more people make this "joke" than actual vegans speaking up. Even when living in LA.
- nothacking_ 2y agoThat's the trick, you invert the logic. If you hear the word vegan, assume the person saying it is not.
- stavros 2y agoThe 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.
- LoganDark 2y agoI 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.
- wisty 2y agoReminds me of the HB100 teardown, but at least this one has an IC to make it more soothing that I don't really understand how it all works. https://www.allaboutcircuits.com/news/teardown-tuesday-hb100-doppler-radar-module/ https://www.allaboutcircuits.com/news/teardown-tuesday-hb100...
- metadat 2y agoToo fantastic not to submit: https://news.ycombinator.com/item?id=40834960 https://news.ycombinator.com/item?id=40834960
- deleted 2y ago[deleted]
- transpute 2y agoI don’t know who designed this, but they were a master of the black art of Radio Frequency waveguide engineering. I am impressed. The PCB, itself, is a major component. Not only for the patch antennas but also several RF filters, the local oscillator, and the mixer are all largely made from peculiarly-shaped PCB tracks. Apart from the PCB, there are only five “components" on the board. Five passive components to implement a Doppler radar module. C’mon. You have to be impressed by that!
- boguscoder 2y agoMCU rp2040 from Pi Pico also costs 1$. We really are in great time for affordable hacking
- robertclaus 2y agoI've played with these all the time! Great to know how they work!
- zer00eyz 2y agoUSB C mm wave "radars" that hook to home automation are a thing. Priced between 11 and 20 bucks they are fairly feature rich... If you want to roll your own check out what the folks over at ESP home have going on (google esp home mm wave).
- stavros 2y agoThe actual component costs about $5, if you want to roll your own with an ESP32.
- mrcsharp 2y agoThe LD2410 (B) is another option and it operates over UART. It is a bit more expensive ~$5 but has more configuration options.
- stavros 2y agoGet the B variant, you can configure it over Bluetooth from your phone. Otherwise it's a huge hassle. That said, it doesn't work very well for me when sitting still 4-5m away, it thinks I've left.
- amelius 2y agoThese radars are designed to detect motion, not someone sitting still.
- mianos 2y agoWrong, 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://github.com/mianos/hk-heltec-radar/tree/main/src https://github.com/mianos/hk-heltec-radar/tree/main/src
- stavros 2y agoThis 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.
- mianos 2y agohere is the ld2450 multi object tracker: https://github.com/mianos/mqttradar https://github.com/mianos/mqttradar It's pretty complete. There was some other guy who wanted an ld2450 tracker so I worked with him to get it going.
- katara2000 2y ago[flagged]
- 037 2y agoA little tangential, but are these things safe for humans? I have a couple of LD2410 devices and I’d like to use one of them with ESPHome in the bedroom. I did some research and they seem to be very low power and safe, but you know, before sleeping with a radar pointing at us all night long, I’m looking for as much feedback as possible.
- rpaddock 2y agoThe site Microwave News keeps up on the latest health aspects of such things. https://www.microwavenews.com https://www.microwavenews.com
- 05 2y agoSome phones have a SAR of almost 2W/kg, compared to that milliwatts of 10GHz RF are nothing. Not to mention that with standard energy dissipation formula of E~R^(-2) you're getting into microwatts at any practical distance from the antenna.
- t0mas88 2y agoI 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.
- 037 2y agoI agree with you, especially regarding children and anyone who hasn’t explicitly made this choice, which is why I asked the question. The only thing is, I suspect we get scared by certain words, like “radar” and “microwaves”, and then we might spend all day with our heads next to a Wi-Fi router or a phone constantly downloading files on 4G. For example: maybe the ESP32 transmitting the bed weight exposes us to more danger than the radar sensor (that can also be placed very far from the bed)? Maybe with our smartphones charging on the nightstand too. I’m not a big fan of fear-based, illogical decisions. But, again, I understand perfectly.
- Barbara230 2y ago[dead]
- jaynpatel 2y ago[flagged]
- hippich 2y agoAlmost 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 external antenna. I tried loaded antenna (i think it is what it is called - the one with the coil) and straight piece of wire. I quickly realized that formula for 1/4 length is more of a starting point, and a lot depends on actual output components of the RC circuit (I have little to no understanding of how all of that works). I tried to cut slightly different sets of wires trying them next to HackRF/PortaPack showing me signal strength in the real time. Basically was eyeballing how strong and clear OOK bursts are, and how well or noisy they sounds through the built-in speaker... (again, I have no idea what I am doing...) At some point I got tired of cutting wires and soldering them, so I tried to cut slightly longer wire and use thin piece of copper tubing to cover end of the antenna at various depth, hoping to simulate the antenna length changes. But at some point something weird to me happened - when just the tip of the antenna was covered by the tube, signal increased dramatically. I am talking about -55db - -50db to -36db on HackRF at the lowest usable gains settings... I ended up with the antenna length slightly below 173mm ideal antenna length with a about 5mm-10mm "cap" made of aluminum foil tape (used for air ducts and such) at the very tip of the antenna. I also closed the other end of this wrap (in my imagination so that the signal does not escape this cap???). The cap itself is electrically disconnected from the antenna, it is just that - a cap. I have no idea why it worked this way. I suspect by adding such a "cap" I modified something related to the capacitance or perhaps there is some resonance thing coming to play - no clue. But it became much more reliable at communicating over the distance I have it installed. Perhaps someone who knows about such things, might give me a clue what I was dealing with. Another thing that probably plays a role in this hack - outdoor transmitter is in the plastic box sitting vertically on a pvc pole, with batteries inside the same box. 1/4 straight antenna would not fit into it, but I also did not want to cut a hole at the top of the box to avoid water intrusion, so I pointed it down. But it also means it goes in parallel with the "USB" cable that connects to the coil-sensor next to the driveway. While system is not grounded, I suspect this USB cable is somehow became part of the antenna, since the best signal was when the line of sight between the antenna and base station, the usb cable was right behind the antenna. Distance between the antenna and usb cable running inside PVC pole is probably about 20-30mm.
- perlgeek 2y agoSince the user manual for this sensor mentions security monitoring as a possible application, I'm wondering: is there any simple way to prevent detection from such a mm wave radar? (Assuming for simplicity that we know where it's mounted, and in which direction it's pointing).
- lindboe 2y agoDepends on the definition of "simple", imo. The first thing that comes to mind is research into materials with good (tens of dB), wideband absorption in the mmWave bands. It's an area of active research [1] [2] (just a couple articles from a quick google, so caveat emptor). [1] https://www.cambridge.org/core/journals/international-journal-of-microwave-and-wireless-technologies/article/abs/broadband-millimeterwave-absorbers-a-review/4A05581C33F5E27E5AAB4CD16EC0D3D2 https://www.cambridge.org/core/journals/international-journa... [2] https://pubs.rsc.org/en/content/articlelanding/2022/tc/d1tc05078h https://pubs.rsc.org/en/content/articlelanding/2022/tc/d1tc0...
- Havoc 2y agoLD2410 work well too (do by the cable too, they have tiny non-standard pins)
- farceSpherule 2y agoYou cannot try to rationalize the prices that China charges for goods. Everything is, more or less, state-owned and state-controlled. If the Chinese government wants to undercut an American product, they will tell the manufacturer to drop the price to X, and the manufacturer will comply. This also does not take into account Chinese currency manipulation. Profit or loss be damned.
- marcinzm 2y agoIsn't the US basically the same? The US government gives massive subsidies, tax breaks or just has the military buy components for 10x the price (to offset commercial loses and R&D).
- kjs3 2y agoNot really. The American system of graft is more transparent. If there's a subsidy, there's a record of it. Tax breaks are public, tho there can be creative ways of couching them so they aren't obvious. Military expenditures are (with some very big exceptions) public record. And a US business under most circumstances can say "I'm not selling below cost". None of this is really true of the Chinese system.
- ein0p 2y agoAnd creates regulatory capture for the rest, e.g. healthcare and big pharma ($4T a year), both of which too charge nontrivial multiples of what the rest of the world pays.
- What2159 2y agoYou make China sound like a VC, Uber, AirBNB, etc ran at a loss to try to own the market.
- dclowd9901 2y agoThe government also stands to benefit greatly if they throw their weight behind smart ideas, just like VCs. It would be interesting if the government could fund itself with investment.