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Our Office have total 70 PostBoxes in one Rack for Staff Members. I want to interface this PostBox Rack with LAN network to send E-mail to every staff member (once in a day) when there is a Post in there PostBox. Each PostBox is made of simple Cardboard and each postbox has approx 12cm height. I want to put sensor in each postbox and I want to interface all these sensor with Bit wise decoder ckt thru Swtching IC so I can read each sensor's output (0 or 1).
I don't want to use any costly sensor or any light or Infrared based sensor. (becos we have total 70 postbox means 70 inputs). I want to use Small piece of alluminium foils (plates) for each postbox as a Capacitive sensor so, when there will be a postal cover in the postbox It's capacitance will change.
Can anybody provide any useful information or any other idea for Cheapest Sensors for 70 postboxes ?
I am also searching for the ckt which can give me 0 or 1 digital output based on that postbox's Capcitance. Postal meterial may be only one post card.
Thanks.
(I am an Electronics Engineer and working as a Project Team Lead for Application Developers Team for the county in US.)
I don't want to use any costly sensor or any light or Infrared based sensor. (becos we have total 70 postbox means 70 inputs). I want to use Small piece of alluminium foils (plates) for each postbox as a Capacitive sensor so, when there will be a postal cover in the postbox It's capacitance will change.
Can anybody provide any useful information or any other idea for Cheapest Sensors for 70 postboxes ?
I am also searching for the ckt which can give me 0 or 1 digital output based on that postbox's Capcitance. Postal meterial may be only one post card.
Thanks.
(I am an Electronics Engineer and working as a Project Team Lead for Application Developers Team for the county in US.)