Determine number of people in a room

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
Ok, here is what I want to do. No I actually did, but I want to know if someone has a different idea on how to approach this.

I want to know if a person ( or more than one) is present in a room and when there is one I'd turn on the light.
I did this a few years ago with a light beam made out of one IR transmitter (the modulated one for IR controls) two IR receivers, a few logic ICs and a triac etc. Not very difficult, I could determine the direction of the person passing through the beam and count the number of people.

However, this whole thing needs a power supply at a place where I do not always have a power outlet nearby and it has more wiring than I want to.

Does anybody have experience with a system that senses the presence of a person?

I do not want to use IR Motion sensors, because the person is not necessarily moving. The person can also be hidden behind some furniture.
The system should also still work when I moved around a chair for example. So simple capacitive proximity sensors/loops might not work.

Only a human beings presence should be detected.
I am not asking for schematics here, just ideas.

Thanks for any feedback
 

TBayBoy

Joined May 25, 2011
148
Sure there is! Carbon Dioxide, water vapor, heart beat...not that any of this would be easy!
CO2 output varies person to person, so I don't think you can determine number of people from that, water vapor would be weather and ventilation dependent.

How about a pressure sensor field across the door floor and determine direction of movement by foot falls?
 

joeyd999

Joined Jun 6, 2011
4,477
CO2 output varies person to person, so I don't think you can determine number of people from that, water vapor would be weather and ventilation dependent.
Don't be so quick to dismiss ideas...you'd be surprised how many things I have done that others thought were impossible. All ideas are good, at least to get the brain juices flowing.

Here's another one: an XBox Kinect.
 

TBayBoy

Joined May 25, 2011
148
Don't be so quick to dismiss ideas...you'd be surprised how many things I have done that others thought were impossible. All ideas are good, at least to get the brain juices flowing.

Here's another one: an XBox Kinect.
Correct, I was pointing out pitfalls, to determine the number of people, I feel we can't use items that would require unique calibration. There are pitfalls in my floor sensor idea, what would happen for a wheel chair?

I would love to hear about your projects, anywhere I can learn I'm game, start a thread, I'll be an avid reader, I might even ask a question or two.
 

Kermit2

Joined Feb 5, 2010
4,162
Traffic lights are sometimes controlled by microwave transmitter devices. They memorize an echo pattern and store it, then create an output trigger when the echo signature is different than the remembered one. Changes which occur to the echo and which remain in the new state for a sufficient period of time are submitted to memory as a 'new' pattern. This allows the device to adapt to new environments yet still detect motion.
 

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
Wow, I liked all of your ideas :D

Just to be sure I made myself clear. The real number of persons is not important. As long as there is more than 0 I want to leave the lights / music / whatever on.

CO2 - the change occurs too slow I imagine.
(Ultra) sound - I thought about that, but then, if I leave a window open or a chair displaced, that would change the sound pattern too
Microwave - maybe a good idea, there is only one difference, cars will reflect MW, so the change in echo pattern is probably substantial. A human will most likely absorb the energy, this also will change the echo of course, but to what degree?

I liked the idea with Sound/MW echo, have to do some research on this.

I understand also, that the device could recalibrate itself after a certain time where there is no change to the echo. But what if I'm reading / watching TV? Or relaxing?

Also, I don't want the device to be needed to be installed, more like plug it in to a power outlet and it works...

What about a true heat sensor, like they are using in contactless thermometers, could that be an option ? never worked with one of those...

thanks for your ideas
 

loosewire

Joined Apr 25, 2008
1,686
How about a scale devices,large squares,so when people move around there exact
weight would be counted to decimals and use a detection system to keep varifieing
that the same weight was moving around,even in wheel chair and average
food comsumption or in case of retail store a magnetic tag would know added weight
to named Item.An Inventory check could be run in the process,we are talking about
smart soft ware Changeing weight would be adjusted for number assigned to Items
1 and for added items,before leaving some attention could be paid to weight Items.
Keeping It non-personal for many reasons.I will keep running this thru the patent office,
you heard It here first. All copy rights protected,under the name of Loosewire for
Id purposes. I am busy on other sites pursueing this Invention.You have sensor cameras
that detect movement already,so If if you have bank of cameras working with other
connecting software that knows the weight in every frame.Any changes with software
could be processed,so using cameras with sensors might be a way to go
with other software.Image recognition could be used,that Is available now that may
work better yet with other high tech software that available.The more I think about
this process,you now have two people asking questions,could I have some advise
on what I have purposed. Come on guys,this Is Loosewire asking for Information.
 
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Thread Starter

praondevou

Joined Jul 9, 2011
2,942
Scale devices are definitely a good idea, even moving items around won't be a problem. BUT, I imagine the installation is quite difficult/complex... :confused:
 

KJ6EAD

Joined Apr 30, 2011
1,581
If one were to tile the entire floor of a dance club with strain gauges, very many interesting things could be derived from the data.
 

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
you could install a rfid under your skin, then whatever room you were in, you could control anything by proximity.

:)
I thought about a passive RFID device. maybe not under my skin, but could be implemented into a bracelet, watch or ring. But it should work for everybody not just the person equipped with a device.

My best guess would be an expensive thermal imaging camera and a software analyzing the captured image. I think it's possible but I'm not a programmer and these cameras are very expensive....

So by now we have:
CO2 - slow reaction time
ultrasound echo pattern- a possibility, this does exist for car alarms, I think, but there is the question of moved furniture and self-recalibrating
microwave echo pattern - similar to ultrasound
rfid - every person has to be equipped with such a device
thermal imaging - too expensive and difficult to develop
strain gauge - works but not easy to install
direction detecting IR light barrier at the doors - works but also not easy to install, maybe if it was wireless, but then how to get power to it??

Any other ideas?
 

steveb

Joined Jul 3, 2008
2,436
How about good old fashioned low tech turnstyles or rotogates. Count them coming and going.

Which brings up the next logical questions.

How do you detect the people that always ask to borrow money, and automatically lock the entrance turnstyle?

Similarly, how do you detect the pretty women, in order to automatically lock the exit turnstyle?
 

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
Which brings up the next logical questions.

How do you detect the people that always ask to borrow money, and automatically lock the entrance turnstyle?

Similarly, how do you detect the pretty women, in order to automatically lock the exit turnstyle?

That's the next step :D

As it is for rooms in a house, I think the turnstyle entrance is a bit too bulky ;) Also, my wife wouldn't agree with the pretty women detection. She could reprogram it to a handsome man detection, and then what???
 

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
Many doorways have the light switch beside them, you could pull power off that.
Yes, I thought of that... Still, best would be not having any external wires. Maybe I can think of something wireless, in this case it only had to transmit power over 1 meter or so.

I'm always amazed how complex a task can be in electronics if even an animal could be trained to do it...
 

ErnieM

Joined Apr 24, 2011
8,183
How about good old fashioned low tech turnstyles or rotogates. Count them coming and going.

I loled.

Roll out some aluminium foil under the carpet and connect to one of those newfangled capacitance sensing switch senors. May only need to recalibrate when you move the furniture.
 

Thread Starter

praondevou

Joined Jul 9, 2011
2,942
I loled.

Roll out some aluminium foil under the carpet and connect to one of those newfangled capacitance sensing switch senors. May only need to recalibrate when you move the furniture.
I don't have a carpet :D

It should be something easy to install, without making too many modifications/mechanical work.
I could also think of something like the SICK safety laser scanners, but they are expensive too and also need to be reprogrammed if something in the scanned field has changed.

There don't seem to be many options... Should be failsafe too, like a normal wall mounted light switch...
 
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