

Ask HN: How to measure if a person is sitting on a chair? - soneca

I have restaurant biz startup. A big problem I have is how to measure the impact of my solution, i.e. measure the occupancy at the restaurants. Neither I, nor the restaurants have a good solution for this. So I thought this could be a business I could provide.<p>So my question is: which technology would be a better aproach to record if there is a person sitting on a chair?<p>Requirements:
- Must be very cheap
- Must record somehow how much time is a chair empty or with someone sitting on it
- Must be reliable<p>I imagine something that could be applied on a sticker. Maybe measuring pressure or something and sending a signal to a hardware when it is occupied. Then this central hardware keep track of the time it is recieving a signal or not.<p>Any ideas?
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jack-r-abbit
My car (like many) uses some sort of pressure/weight sensor to detect if a
passenger is sitting in the front seat. If there is not (or they don't meet a
certain weight threshold, like a child) then the passenger side airbag is
turned off. Those are probably bulkier than you'd want on a restaurant chair
but you can probably tuck a decent sized box under the seat and no one would
notice/care. Anyway, I would say some sort of pressure sensor is the way to
go.

Edit: you might even be able to use something a little more passive. If the
chair was equipped with a small, low-power RFID tag that had enough logic to
simply toggle its state [vacant|occupied] based on the pressure sensor, you
could then position an RFID reader somewhere in the dining area that
periodically polled the devices in the chairs. Then you don't have to worry
about the chairs having enough power to run an active device.

~~~
soneca
Sounds the way to go. I am googling "passive rfid tag with pressure sensor".
Some promising solutions...

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junto
Stick an RFID tag on every customer's posterior when they arrive at the
restaurant.

Bingo, now you can track which rear end is sitting where.

Seriously though, there are some good options with RFID tags. Does it really
have to be per chair, or could it be people per table?

You could put an RFID chip on each menu (though the menu would need to be left
at the table for the duration of the customer's visit, and you would always
need to provide 1 menu per customer).

If you didn't want to use menus then you could use something else instead, as
long as you could RFID tag it.

When you go into clothes store changing room you often get given a tag with a
number on it. That tag number defines that number of clothing items you have
taken into the changing room with you and it reduces theft.

You could operate a similar system, but based on the customers sitting at the
table. It won't tell you which seats are being sat on, but it will tell the
occupancy per table.

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ilyaperepelitsa
there is usually a number of guests in the receipt, cheek the time at which
your client paid and time he/she made an order

~~~
akg_67
IMO this is the most realistic and cost effective solution to problem. Most
restaurant POS systems that handles reservation, seating and billing should be
able to provide needed info.

Any RFID or sensor base system will be complex, cumbersome and costly. Any
passive sensor will require manual scanning. Any active sensor system with
receiver will be expensive specially for restaurant with large seating area.

Another option may be an incentive based passive RFID sticker. A guest
receives a sticker upon arrival and gets some sort of incentive/reward on
scanning the sticker at exit. Then you can capture the time in the restaurant
or on the table.

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pruth
Maybe you could use a simple pressure sensor hooked upto bluetooth and check
to see if there are variations over short periods of time to make sure theres
a person on it.

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byoung2
I imagine you'd have to match up multiple measurements to get an accurate
count. A busy happy hour will throw off your numbers because you'll have 20
people sitting but 50 more standing who won't be counted.

Are you interested in just the number of people in the restaurant? Or, more
importantly, how many people are ordering food? Because you could have a table
of four share a $10 appetizer and you'd count 4 people.

~~~
soneca
Ideally I would account for all of it. But I need to start somewhere, and I
don't think looking for all-in-one solution is a good path. So just know how
many people are sitting and don't care what they are ordering or who is
standing up, is enough for now.

~~~
pruth
Why not just track the number of people who walk in and out?

How much added value does the sitting aspect add, considering that it would
cost a lot of if you had to retrofit these onto your seats?

~~~
jack-r-abbit
Knowing how many people walk in and walk out tells you how many customers you
served but can't tell you how long any one of them stayed. Knowing how long a
specific seat was occupied can.

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Qworg
I'd look at patents. There are several expired patents for seat occupancy
sensors that rely on EM wave disturbance. They're in pretty much any "auto
off" passenger airbag system.

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lifeisstillgood
Camera counting - every chain store these days has a camera at the front door
counting people in and out - seems a well known, commercialised and direct
solution.

