doorknob alarm pcb


Posted on Feb 5, 2014

Circuit Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected by the electrical capacitance change that occurs from the human hand contact between the kn


doorknob alarm pcb
Click here to download the full size of the above Circuit.

ob and the box. Almost all of the commercial devices sold use a more expensive and power consuming radio frequency circuit approach to detect the capacitance change. But, a very inexpensive and micro power technique can also work. This circuit schematic should dramatically reduce the cost of the device and allows it to operate for many years from one set of batteries.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Simple 2M 6M Transverter Circuit
    IC 723 TIP41 Laboratory Power Supply Variable voltage
    Audio Booster
    Symmetry Feedback Maximizes Function Generators Linear Sweep Range
    Wire loop alarm
    Puxing 777 Radio Headset Schematic
    12dB-oct by the OP amplifiers low-pass filter



    Top