j0e
Posts: 9
Joined: Tue Jun 18, 2013 12:15 am

Sensors for human detection

Tue Jun 18, 2013 4:19 am

Hello everyone! this is my first post, so I hope i'm asking this in the right place :)

First of all, Raspberry Pi is just awesome, I'm having a great time installing, configuring, programming, erasing and doing all over again, just for the sake of learning something new each time.

Introducing my question: I'm having fun working on a home automation project. It's a RPi web server for user interface and data storing (Apache, PHP, MySQL, DNS), a data logging daemon I'm programming myself for the serial port, and an XBee radio. The setup allows many different combinations of sensors + actuators. The first thing I did was light detection with a photocell, so a LED lights at night. I was thinking it would be nice now to try out something related to home security.

The question: Which sensor, or combination of sensors would be a good way to go for human detection? As a starting point, I'm thinking about using a PIR sensor, but this sensors also would detect my dog, so maybe adding a second sensor combined with the PIR will make a good combo for this. Any ideas?

Thanks!! ^^

techpaul
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Re: Sensors for human detection

Tue Jun 18, 2013 9:23 am

The only simple sensors are PIR, which has limitations, so does ALL types of sensors. To do this with any other types is not simple to work out the difference between the dog and human or child, without a lot of work, to determine sifferences for different objects at different distances and different positions.

A teenager on all fours could easily be confused with a German Shepherd by nearly all systems.

This is not a simple difference to do by any single sensor.
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or http://www.pcserviceselectronics.co.uk/pi/

j0e
Posts: 9
Joined: Tue Jun 18, 2013 12:15 am

Re: Sensors for human detection

Wed Jun 19, 2013 12:20 am

Well, what I had in mind was a combination of sensors, not just one sensor that does the perfect job, but maybe this doesn't exist. Anyway I'll start trying different setups for a cheap and more reliable human detection with 2 or 3 sensors combined. If there is someone with any theory about this, or just thinks this is possible (like me), I'll be glad to do the research with him ^^

My first guess was combining the PIR with one or more obstacle detection IR sensors installed near the ground, but higher than the height of my dog. The flaw I see is a man crawling down the lower sensor, or just passing by the side of the IR sensors if this is installed in an open area.

gritz
Posts: 449
Joined: Sat Jan 28, 2012 2:33 am

Re: Sensors for human detection

Wed Jun 19, 2013 12:56 am

It's an interesting problem (and one that I have absolutely no expertise in, so apologies in advance for my speculative approach)

Pattern recognition in any form obviously relies on the target vaguely resembling something recognisable. A potential target (detected by infra-red, or movement, etc.) could be coaxed into unwittingly "posing" or otherwise responding to an audio / visual cue, making subsequent evaluation easier . Humans can be predictable! This would obviously be easier in a controlled space than in an acre's worth of back garden, but e.g. two cameras can give distance information and from that dimensions can be inferred.

I'm sure that you wouldn't be the first to have a stab at something like this - I wouldn't be surprised if someone on this very board will be able to point you in the right direction. Perhaps hackers of the Kinect can yield some clues too.

Sorry I can't be any proper help! :)

mikerr
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Re: Sensors for human detection

Wed Jun 19, 2013 12:00 pm

techpaul wrote: A teenager on all fours could easily be confused with a German Shepherd Dog by nearly all systems.
You could have the dog have a bluetooth collar and ignore the sensor when he's in that room,
see this thread for how to do BT proximity:

http://www.raspberrypi.org/phpBB3/viewt ... 37&t=47466
(maybe use an old bluetooth earpiece)
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techpaul
Posts: 1512
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Location: Reading, UK
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Re: Sensors for human detection

Wed Jun 19, 2013 4:19 pm

mikerr wrote:
techpaul wrote: A teenager on all fours could easily be confused with a German Shepherd Dog by nearly all systems.
You could have the dog have a bluetooth collar and ignore the sensor when he's in that room,
see this thread for how to do BT proximity:

http://www.raspberrypi.org/phpBB3/viewt ... 37&t=47466
(maybe use an old bluetooth earpiece)
After seeing recent TV prog about cats, where cats go into neighbours houses to pinch food, bluetooth all possible animals nearby :lol:
Just another techie on the net - For GPIO boards see http:///www.facebook.com/pcservicesreading
or http://www.pcserviceselectronics.co.uk/pi/

j0e
Posts: 9
Joined: Tue Jun 18, 2013 12:15 am

Re: Sensors for human detection

Wed Jun 19, 2013 7:15 pm

Well, maybe it would be not a 100% solution, but it adds a lot to it. Actually I think it's a great idea, to have some sort of identification device with family members and dogs, like bluetooth (maybe XBee too, as it has an RSSI indicator as well), or some RF id system. And this wouldn't be expensive too, considering that this may be used for the whole system as a way of logging in to a personal profile over the house to control lights, doors, etc. Anyway, I think we all understand that there will never be a 100% solution, every security system has its flaws, but minimize them is what we can do!

Cats/birds are the problem now. Does anyone know some sort of sensor that can sense the size of an object? This would finish the job imo. Other solution, also, might be to put some obstacle detection sensors over the areas where usually cats pass through (a house specific solution).

techpaul
Posts: 1512
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Location: Reading, UK
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Re: Sensors for human detection

Wed Jun 19, 2013 7:45 pm

j0e wrote:Cats/birds are the problem now. Does anyone know some sort of sensor that can sense the size of an object? This would finish the job imo. Other solution, also, might be to put some obstacle detection sensors over the areas where usually cats pass through (a house specific solution).
The biggest part of working out size is working out distances, otherwise a close object may appear bigger than a distant object. Some form of 3D distance measurment of all objects in view helps.

Also be aware of large objects partially hidden e.g. person walking behind a sofa and you only see top half.
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or http://www.pcserviceselectronics.co.uk/pi/

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