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I have to create simple device for a promotion campaign. I should react when someone seats on the chair, so I need advice on choosing the right sensor. Should it be pressure sensor and what kind is better for Raspberry Pi?

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    \$\begingroup\$ FYI there's a stack exchange dedicated to the RPI: raspberrypi.stackexchange.com \$\endgroup\$ Mar 1, 2013 at 21:30
  • \$\begingroup\$ @AnalogArsonist oh, I didn't know, thank you! \$\endgroup\$
    – Mee
    Mar 2, 2013 at 8:25

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If you just need to detect someone sitting on a chair, you just need to connect a pressure-switch or mat to one of the GPIO pins & read the status. There is plenty of info on this on the RaspberryPi forums.

A robustly-sprung push-button switch on one of the legs could also do.

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A microcontroller running a large capacitive sensor under the seat cushion sounds like it would work. That can then communicate with another computer in various ways. Via a serial port is probably the easiest considering both sides. If your computer doesn't have a serial port, then use a off the shelf USB to serial adapter.

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  • \$\begingroup\$ To whoever downvoted this, why do you think capacitive sensing is bad advice? It has some advantages like being easily hidden, easily sealed, no moving parts to wear out, and very thin so that after the sensor is added the chair can look and feel the same. It may not be what the OP wants, but I don't see how its a wrong answer given the sparse requirements in the question. \$\endgroup\$ Mar 1, 2013 at 16:24
  • \$\begingroup\$ I'd suggest that a solution involving USB/UART comms / capacitive sensing may be considered overkill for detecting if a chair is in use or not. Just MHO, I tend towards the simplest-possible solution. \$\endgroup\$
    – John U
    Mar 1, 2013 at 18:01
  • \$\begingroup\$ @John: Different things are simpler depending on constraints. If this computer has a digital input, then the capacitive sense can be hooked to that just as well. The question then is what is the better way to detect someone sitting on the chair. Different methods have their advantages/disadvantages. Which one is more appropriate or "simpler" is very context and requirement dependent, something the OP has told us very little about. \$\endgroup\$ Mar 1, 2013 at 18:11
  • \$\begingroup\$ @JohnU Cap sensing probably has a lower false trigger weight than simple pressure sensors, if someone moves around or shifts their weight on the chair. \$\endgroup\$
    – Passerby
    Mar 1, 2013 at 19:09
  • \$\begingroup\$ @Passer: Then there is also the issue of how exactly to mount the pressure switches. They have some mechanical bulk, so you can't just slide one under a thin seat cushion. This is solvable, but certainly makes the system less "simple". \$\endgroup\$ Mar 1, 2013 at 19:29

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