Consider a chemical factory. Certain rooms may never be empty (control room, security, etc), some have a limit on how many people may be there at any give time, and some contain hazardous materials and no one may stay in there longer than a certain time. Beyond that, in case of evacuation it is necessary to know where everyone is.

I am thinking of wearable badges, probably with WIFi (*) and readers at every door, to scan those entering & exiting.

I could make something cheap and small with a $5 Raspberry Pi Zero and a $2 USB WiFI dongle.. or, maybe BlueTooth, but what about a battery?

Of course, passive RFID wouldn’t require a battery, but could I be certain of reading everyone who passes through a doorway (and what about a very wide door, such as might be found in a factory)?

Really, all that I need is a way to identify people as they pass through doorways flanks by readers. Computing power is not required, but since the Raspberry Pi Zero is so dirt cheap, I might be able to find some other uses (attach a mic & speaker? Any other ideas?).

If I do need a battery, then given an 8 hour working day, plus breaks, plus a margin, then I need 10 or 12 hours battery life.

Does anyone know of an of the shelf solution? Failing that, some thing easy to put together from off the shelf parts?

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    Look into Active RFID. The range is a lot further and you can also use it to geo locate people in the factory. I don't have time now but can do a write up on it later. I looked at using it to track the location of my employees at one point in time but decided cameras were fine.
    – Jeff
    Feb 24, 2017 at 0:02
  • Hmm, cameras are also an option, with good facial recognition. Feel free to post an answer about active RFID (and a second about cameras ;-) Feb 24, 2017 at 8:45
  • Hmm, @Jeff, how does the cost of various methods work out versus their effectiveness? I suppose that facial recognition might miss out if someone turns their head or looks down when entering or leaving a room, but I Can always pick them up in the next room. Can you comment on the accuracy, the cost and how easy it is to integrate such a solution into my own software? Feb 24, 2017 at 16:05
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    We did not use facial recognition on the cameras unless you consider my eyes facial recognition. I did mean to ask you what your budget was as well as will you have network access at the doorways or will it need to be wireless. Other consideration is how many doors are you looking to monitor and how far away are they from each other. The scanners are the expensive component about 1000-2000 each. The tags are cheap about 5$ for a wearable wrist band.
    – Jeff
    Feb 24, 2017 at 16:24
  • I had been going off the idea of cameras, in case employees objected on privacy grounds. I cannot see iris scanning working, as it slows entrance & exit, plus it requires removing protective googles. I don't have a budget, other than my own pocket. A guy I know does business with a chemical plant, which frequently tells him it needs such a solution, but is unlikely to part with any money until at lest a proof of concept is shown. Overall cost will play a role in saleability, no I guess cheap, but works well is what I am looking for. RFID? Feb 24, 2017 at 16:30

1 Answer 1



Long range Passive RFID will cost you around $45 so forget about it..

Cameras to follow employee! science fiction, we are not ready for it yet..

GPS will not work perfectly inside buildings..

But there is a small idea for you and more simple!

I worked on AP devices from company called ubiquiti, These AP have the ability to work as a mesh network, there is an option to make a a Clint move around while the network choose the better WiFi AP for him and connect it directly..

I used to follow my friends inside this network by calculating the distance between them and each AP. So acttully you will know their locations from their Mobiles like how GPS work..

Throw 3 AP inside a company, it will work as WIFI and tracker at the same time, with a small script you can make this thing work.. enter image description here

There is a company working on that idea anyway check this link

  • If you mean $45 per tag for the Long range Passive RFID , Ali Express doesn't agree with you. However, I do like this answer! Feb 25, 2017 at 14:58
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    Not the tag! the reader, for short distance it's around $2 but for the long one "big doors" around $45 goo.gl/xWLHvD
    – Narzan Q.
    Feb 25, 2017 at 16:06
  • Loxl! IC IC . Well, I can afford one for development (or cheat & use short range). If there is any interest shown then I will buy a few for real demo & I can't see a chemical factory baulking at $45. Feb 25, 2017 at 16:09
  • BLE 5.1 is looking good, with AoD & AoA giving direction and distance to within one metre Feb 27, 2020 at 11:29
  • your AliExpress link says "Sorry, the page you requested can not be found:(" Can you give a product name? Feb 27, 2020 at 12:48

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