A sensor to measure people...

John Bond

I have·an application where I need·a sensor that is mounted above an open·door and records the number and direction of the people passing through the door. I can think of many complex ways of doing this but ther must be a simple solution.

Please give me your ideas and input

Thanks a stack and kind regards from Darkest Africa.

John Bond

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Morrolan

Counting the number of people obstructing a doorway can be done with the Parallax PING))) sensor mounted above the door pointing down by monitoring the change in echo time.

The problem with this is, it will only count how many times the sensor is obstructed, and if in your code you then required a "reset", i.e. the PING))) must measure the full echo time to the floor before it allows another count, you will get innacuracy if people are pressing tightly together through the doorway.

For directionality - have 2 doors, one in, one out!

OR... If you can guarantee that only one person at a time will walk through the door - you can have IR break-beam sensors on either side of the door, i.e. one inside and one outside. You could then record which sensor was triggered first to determine which way the person is walking through the doorway if that makes sense?



Good luck mate!
Morrolan

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Flying is simple. You just throw yourself at the ground and miss.

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
Stephen Hawking

John Bond

Thanks for your very quick response Morrolan

My complex solution was to have two ping sensorsin the doorway, angled at say 10 Deg and I would watch the order in which they were broken. One may get two people walking in together but, because South Africans consider it bad manners to one to walk through a door in the opposite direction to someone else, we won't get two people in a doorway going in opposite directions at the same time.

I can't use break-beam because these sensors will be mounted above a doorway and some of the floors have carpet, other ceramic tiles and others Lenolieum (a plastic floor covering)

I can use IR beams but I've never used them at a distance of greater than an inch. I need a fairly high level of reliability.

That's where I am at.

John Bond

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Javalin

what about a thermal array sensor from www.robot-electronics.co.uk

?

John Bond

I hadn't thought of that, I've got one in my parts bin. I'd need two and then maybe mount them in pipes to make them more directional...

Thanks Javalin.

John

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Morrolan

2 Ping's with a narrow focus would work, but I wasn't thinking of having the IR break-beam sensors above the door, but across the doorway about 3 feet high...

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Flying is simple. You just throw yourself at the ground and miss.

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
Stephen Hawking

skylight

the most robust and accurate way would be turnstiles surely?

John Bond

Thanks for your input...

This is a shop entrance so turnstyles wouldn't be appropriate.

The doors open inwards and the sensor has to be mounted on the inside of the store so that restricts me to the top of the door frame. The doors are also usually 2M (6 foot) wide which may cause problems for the Ping. I'll do some trials on Sunday...

I'll also do some work on IR heat sensing...

Regards
John

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Steel

I would think that the easiest AND cheapest solution would just be use an IR Emitter and Detector...when the beam is broken, count that as a person...

Javalin

or two close together, i.e. beam 1 before beam 2, then going in - and vice versa.

J

Phil Pilgrim (PhiPi)

Because the entrance is so wide, two people could pass through abreast, and a transmissive IR sensor pair would never know it. You would need a pedestal in the middle of the doorway and two complete sets of sensors to eliminate this possibility.

-Phil

PLJack

John Bond said...
Thanks for your input...
I'll also do some work on IR heat sensing...
Regards
John

I would be very thankful for any thermal solutions you find useful.
I looked into thermal sensing a few months ago. I really think it would work.
In my case I want to install sensors on half a dozen doors.
I could not find a a solution that was inexpensive enough to be worth the effort.

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- - - PLJack - - -

---

Perfection in design is not achieved when there is nothing left to add.
It is achieved when there is nothing left to take away.

John Bond

Thanks for the really useful input. I'm playing with the heat sensor this weekend. Trouble is I don't know how to get information on the direction of the customers using a heat sensor. Possibly use two...

Usually two people walking in to a shop together are together and will get served together. This doesn't worry me too much. (the large US system that you see in some shopping centres "Malls" counts legs to get greater accuracy).

I can't use a break-beam sensor because I can't mount across the doorway, I can only mount above the doorframe.

Sharp make a distance sensor similar to the one Parallax used to sell called GP2Y0A02YK but it's range is too short, only 1.5M

So that leaves me with thermal sensing and the Ping.

If I use the Ping, I can reduce the number of sensors by angling the Ping at say 20Deg from vertical and measuring distance. If·distance decreases, the person is walking away from the sensor and if it increases, they are approaching it.

Kind Regards
John Bond

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Post Edited (John Bond) : 10/16/2007 6:37:03 AM GMT

kelvin james

An idea would be to use pressure mats as inputs, one on the outside and one on the inside. Timing parameters between the two could be set up to determine direction, and to deal with possible errors.

John Bond

Hey Kelvin, that's an idea. I'm going to look into that...

Regards
John

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