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?

  • 1
    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 '17 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 '17 at 8:45
  • Say what now? Where was the sarcasm? If you find it in "feel free to", that was my polite way of saying "pretty, pretty please" - I wanted an answer, of course - with more detail, but was saying that even if @Jeff had only posted "use cameras", I would accept it as an answer.. If you find sarcasm elsewhere, please point it out and I will retract it, as there was certainly no sarcasm intended (note that I didn't use the sarcasm tag :-) Feb 24 '17 at 15:38
  • 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 '17 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 '17 at 16:24


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 '17 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 '17 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 '17 at 16:09
  • BLE 5.1 is looking good, with AoD & AoA giving direction and distance to within one metre Feb 27 '20 at 11:29
  • your AliExpress link says "Sorry, the page you requested can not be found:(" Can you give a product name? Feb 27 '20 at 12:48

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