need a bracelet or watch that can communicate via radio - Page 1
Forum section: electronics / general

author: DiTBho
author_rank: Super Contributor
timestamp: October 26, 2024, 04:09:16 pm
content: I need a bracelet or watch that can communicate via radio, and return (to a GNU/Linux embedded system) the gps position.it must work within only 50 meters from the antenna, but it must also work indoors.I need to write myself the application.What do you suggest?(I know, weirds specs)

author: Andy Chee
author_rank: Super Contributor
timestamp: October 26, 2024, 04:15:53 pm
content: What kind of position resolution do you require within that 50 meter boundary? GPS might get you within 1 meter, but once indoors you're going to lose accuracy as you lose satellite lock.

author: DiTBho
author_rank: Super Contributor
timestamp: October 26, 2024, 04:19:12 pm
content: Quote from: Andy Chee on October 26, 2024, 04:15:53 pm+/-5 meter is OK

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 26, 2024, 08:29:48 pm
content: GPS indoors is a gamble. You just can't reliably count on that.The only kind of GPS receivers I've used "successfully" indoors had a pretty large antenna (like 50mm x 50mm) and would draw significant power. Not something that would easily fit in something like a watch.Even so, that wouldn't work 100% in all rooms indoors and +/-5 m would be sort of achievable only near windows.But if your goal is to locate a device relative to another with a 50m max distance, then there may be better approaches than using GPS.

author: DiTBho
author_rank: Super Contributor
timestamp: October 26, 2024, 11:16:00 pm
content: Quote from: SiliconWizard on October 26, 2024, 08:29:48 pmmy Garmin 830 has no problems with GPS when it's used indoorsQuote from: SiliconWizard on October 26, 2024, 08:29:48 pmDevek created asensorthat locates your umbrella when you forget it somewhere.It sends a signal to your smartphone and can tell you roughly the GPS coordinates of where you left your umbrella.How do they do it? It's a sensor powered by a small battery.I need to let people know where I am in a large room of 50m x 50m.What other solution do you have in mind?(I can't put sensors on the floor, or use cameras or anything)

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 27, 2024, 12:43:36 am
content: Quote from: DiTBho on October 26, 2024, 11:16:00 pmIf you can't add any more infrastructure to the room, the only automated way I can think of is to look for Wifi APs and estimate the position based on relative signal strengths.Or maybe use a near IR beacon and the ones that have to know where you are use their smartphone cameras to look for the beacon? (Probably have to use 850nm or 740nm LEDs to work reliably, the more common 940nm wavelength is blocked by a lot of modern smartphone cameras.)

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 27, 2024, 01:07:22 am
content: Quote from: DiTBho on October 26, 2024, 11:16:00 pmFrom what I can tell, it's a very "simple" device that only connects to a phone, most likely via Bluetooth and acts as a "beacon" of sorts. The paired app on the phone will constantly monitor it and if it doesn't detect the beacon anymore, it signals it. I don't think it gives much more info than this. Maybe they can manage to give an estimate of the distance between the device and the phone - as long as it's within range, so about 30ft, 10m - using radio tricks. This is the typical range for BT. As I read the specs, it only tells you once it's out of range and at this point, it can't tell you where it is, but only where it was last "seen".BT has added distance "awareness" in recent versions:https://www.bluetooth.com/learn-about-bluetooth/feature-enhancements/channel-sounding/I don't know if that's what they use, if they actually estimate the distance or if it's just a "present/absent" notification. In the latter case, all you need is to implement a BT device and pair it to a phone. If it disconnects, then it's probably out of range. If it stops being within range, it's lost. Nothing can be tracked further.There are some RF SoCs that can do distance estimation, but it's relatively coarse. I've seen the SX1280 in particular, which is a 2.4GHz Lora chip with a "ranging" feature:https://www.semtech.com/products/wireless-rf/lora-connect/sx1280I don't remember it can achieve anything like +/5m though. It's more meant for longer distances and with an errror of over 10m IIRC.One other "typical" approach is using UWB - Decawave had some solutions, it's now part of Qorvo:https://www.qorvo.com/innovation/ultra-wideband/technologyit was precisely meant for indoor communication and positioning. They have chips and dev kits:https://www.qorvo.com/products/wireless-connectivity/ultra-widebandYou can otherwise have a look at this:https://www.u-blox.com/en/product/u-locatetagit does require installing "anchor points" in the area of interest, but that's not a heavy installation in terms of infrastructure.

author: Buriedcode
author_rank: Super Contributor
timestamp: October 27, 2024, 05:29:24 am
content: Quote from: DiTBho on October 26, 2024, 11:16:00 pmSo whats stopping you using that?

author: DiTBho
author_rank: Super Contributor
timestamp: October 27, 2024, 12:52:30 pm
content: Quote from: SiliconWizard on October 27, 2024, 01:07:22 amDavek can customize umbrellas with your company logo,corporate gifting program. They gave me a high-end one, and ... knowing that it costs >300 euros ... I was terribly afraid of losing it.... terribly afraid of losing itDo you know how embarrassing that would be for the customer who kindly lent it to me for the duration of the trip?So I carefully read the instructions and installed the Davek app, and I can tell you that it doesn't just warn you - "hey, oh? you're probably forgetting your umbrella!!!" - which by the way on my Motorola G85 it rings and vibrates the same way my morning alarm work, but can also give you the GPS coordinates, with a precision of +/- 10 meters, of the last time the phone received the signal from the sensor.At this point I think it's the phone's GPS, and not the sensor's, that gives the position.Checking permissions, I see the Davek App wants to access the phone GPS

author: DiTBho
author_rank: Super Contributor
timestamp: October 27, 2024, 01:08:05 pm
content: Quote from: Buriedcode on October 27, 2024, 05:29:24 amWell, the Garmin 830 is a bicycle computer, very expensive, it costs about 300 euros (wihtout sensors), even if it has just been replaced by the Garmin 840/Solar, which costs about 500 euros (without sensors).Just to give an order of costs ...But apart from that, it is not an "open source" device, it communicates via wifi with the smartphone through closed applications, created by Garmin, whose protocol is not known at all, so it would not make sense to "hack it" (love that, but) just for the tracking application that I have to create.The point is/was: that thing has a very small integrated antenna, and it has a GPS, all things that in theory should not work, and yet they also work indoors, even inside the train station on the surfaceI don't want to buy an Apple-Watch or that "hi-tech" stuff like the Garmin Phenix smart watch: they are too bloody expensive (>> 1200 euro) . So, sometimes, if I go out for a run during my lunch break and take roads I don't know, in places where I've been exploring on a business trip since a few days, I carry the Garmin 830 with me on a wrist strap and use it as an "urban navigator".One device, bought specifically for training and bicycle rides, I also use it for running, but that's all I am willing to do with it

author: EE4all
author_rank: Regular Contributor
timestamp: October 27, 2024, 02:36:56 pm
content: Find you in a large room? Well, this room must be very crowded. I think you and other party needing to find you will both wear hats with cheap laser pointers pointing to the ceiling, and look for each other's ceiling dots.Jokes aside, there are possibilities outside of the RF portion of the EM spectrum that you could play with.

author: DiTBho
author_rank: Super Contributor
timestamp: October 27, 2024, 02:54:53 pm
content: Quote from: EE4all on October 27, 2024, 02:36:56 pmActually there are 5..12 people, it's a showroom, but if I can track my position inside the room, I can easily write a distributed application (GNU/Linux + Haiku) that instantly posts the work session(1) on the terminal I approach, without having to enter the password or other very annoying things when I have to show the customer things and it would also make a good impression, very technologically and clean.(1) kind of SunRay, but made from scratches, operating on vt220 and X11 (I mean documented session protocols), and without multiple smartcards (one for each terminal/position in the room) to load/save the sessions.Quote from: EE4all on October 27, 2024, 02:36:56 pmcan you give me more details?

author: EE4all
author_rank: Regular Contributor
timestamp: October 27, 2024, 03:32:20 pm
content: Ah, ok, I get the use case now. Why not put NFC tags at each spot, swipe your smartphone at each station, and use Tasker or similar automation on the phone to call the backend tasks you want?

author: ebastler
author_rank: Super Contributor
timestamp: October 27, 2024, 05:30:52 pm
content: Quote from: DiTBho on October 27, 2024, 02:54:53 pmAs EE4all said -- this seems like an obvious use case for somelocalidentification at each terminal. NFC, BLE, whatever. There are various off-the-shelf solutions for unlocking Linux and Windows computers when you approach them with your smartphone. I believe that includes solutions which can log in different users. No swiping needed, it could occur "magically" when you approach.I would expect that to be much more precise and reliable than an approach which locates you "globally" in the area. Which is important when you want to impress customers: You don't want to stand there and not be able to log in. And you don't want your session to open unintentionally on an unattended terminal across the room where visitors can mess with it.