table presence

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ewaldharmsen
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table presence

#1 Post by ewaldharmsen » 11 Oct 2018, 19:24

Hello all,

I have a dining table made of wood.
To if the lights above the table should go on I have mounted a PIR(with smallest sensitivity) in the ceiling above it.

However it is not working well for two reasons:
1) When it is dark and I walk by the table on lets say a 2 meters distance, the lights go on, but they shouldn't
2) While eating the lights go of because we do not move enough.

So my question does anybody another sensor I could use to see if we are at the dining table?

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enesbcs
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Re: table presence

#2 Post by enesbcs » 11 Oct 2018, 20:50

ewaldharmsen wrote:
11 Oct 2018, 19:24
Hello all,

I have a dining table made of wood.
To if the lights above the table should go on I have mounted a PIR(with smallest sensitivity) in the ceiling above it.

However it is not working well for two reasons:
1) When it is dark and I walk by the table on lets say a 2 meters distance, the lights go on, but they shouldn't
2) While eating the lights go of because we do not move enough.

So my question does anybody another sensor I could use to see if we are at the dining table?
Some wild idea:
- You can mount some distance meter's at the ceiling above the chairs and if anybody sits on it, the distance is shorter. :)
- Or you can use some sort of weight sensor installed under the chairs to know if anybody on it...
- Or with some DIY methods install a simple button on the surface of the chairs (extra pillow, wood panel?)

TD-er
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Re: table presence

#3 Post by TD-er » 12 Oct 2018, 01:24

There are also 'radar' sensors, which cost next to nothing.
These detect motion, but the 'problem' is they detect it all around them and even behind.
But this can be directed/shielded using metal.
So you could try to experiment by mounting such a sensor in a lamp above the table, or even mount these sensors below the table. (detection also works through almost all materials)

You really have to sit still to not let these sensors trigger, but like I said, it takes some time to get them directed to cover the range you'd want.
Also mounting metal too close to the sensors will make them stop working at all.

But since these sensors only cost about 50ct each, it is nice to play with them and maybe you can mount several to cover a specific part of the table.
And make sure to cover the 'back' of the sensor with metal, or else you will "see" people at the other side of the ceiling/wall/floor moving.

N.B. also water drops on leaves of a tree moving in the wind can trigger these sensors, so it takes some experimenting to lower sensitivity and directionality.

Shardan
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Re: table presence

#4 Post by Shardan » 12 Oct 2018, 12:21

A really working presence check would be very appreciated.

for a few applications there are some possibilities...
For my appartment I use a bluetooth based presence detection for "at home"/"Not at home".
But sadly that won't solve your problem. PIR and radar based sensors won't solve it either,
their behaviour is similiar in this point: They need movement.

One possible solution: A CCTV camera with moving detection.
These cams are used for alarm systems, good cams have a relay contact for alarming.
This solution may work, a motion detection on a computer or Raspberry even better, as
sensivity can be controlled. This solution is expensive and might not be very welcomed
by everyone.

A more simpe solution might be to install one or more ultrasonic sensors under the table.
They should be placed to work on short detection distances - that needs several sensors
to get every place. Avoid aiming at the table legs.
This solution seems the one with best chances for DIY to me.
What might be a problem is using many US sensors - I've no experience if they interfer
with eachother. Needs some testing I think.
Regards
Shardan

HomeJCL
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Re: table presence

#5 Post by HomeJCL » 13 Oct 2018, 09:28

Yup several U.S. sensors is nog the best to have a reliable “Group session” :D

The advantage of US it detects a fixed distance, you only need one.
If using the table with 1 reference seating and will allways be used with this reference seat.

PIR and radar are I think too sensitive and finicky to setup where US or laser sensor if distance from ceiling/lighting permits, at the same time from ceiling solves power supply.

Anyway I like the idea, my list of todos for the winter just got 1 item more on it, it looks like I will need 4 winters to do evrything :roll:
Belgium and land of ESP ... counting :D

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enesbcs
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Re: table presence

#6 Post by enesbcs » 11 Nov 2018, 09:50

Another idea:
I2C thermal camera? :)
https://www.adafruit.com/product/3538
You can even tell if there is hot soup on the table...

HomeJCL
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Re: table presence

#7 Post by HomeJCL » 11 Nov 2018, 17:57

Yup there goes definitely the last free hours I had planned for the winter :lol:

Thanks ;)
Belgium and land of ESP ... counting :D

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