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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

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Sensors / Detectors: Motion Sensors Circuits

Alarm Discriminator + Battery Monitor of the Electric Field Disturbance Monitor  -  This schematic is the alarm discriminator plus the batterry monitor of my "Electric Field Disturbance Monitor".  The system can detect human and animal motion by the electric fields they disturb . . . [Hobby Circuit designed by David A. Johnson P.E.,  03/26/02]


Detector for Human Footsteps  -  This circuit uses a surplus geophone to detect human footsteps from 100 feet away. It was designed for monitoring the Mexico/USA border. This preamp part of the system draws about 50 micro Amps from a 12 volt supply . . . [Hobby Circuit designed by David Johnson P.E.,  07/11/06]


Detects Shadow Activated Motion  -  This circuit can sound an alarm when the shadow of a hand or arm moves over  two small photo diodes . . . [Circuit by Dave Johnson P.E.,  08/21/05]

Earthquake Alarm Circuit  -  Geophones are dandy motion sensors.  They are metal cans containing a powerful magnet, suspended with springs inside a coil of wire.  The magnet functions as a floating mass.  The slightest vertical motion of the device causes the coil to move relative to . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/08/05]


Electric Field Disturbance Monitor-Alarm Discriminator + Battery Monitor  -  This schematic is the alarm discriminator plus the batterry monitor of my "Electric Field Disturbance Monitor".  The system can detect human and animal motion by the electric fields they disturb . . . [Circuit by Dave Johnson P.E.,  03/26/02]


Electric Field Disturbance Monitor-Front End + Power Supply Circuit  -  This schematic is the power supply and front-end sections of my field monitor, "Electric Field Disturbance Monitor". The system can detect human and animal motion by the electric fields they disturb . . . [Circuit by David A. Johnson P.E.,  03/26/02]


Footstep Alarm for Human Traffic  -  This circuit processes the Amplified signals from the footstep detector circuit and activates a microprocessor when the circuit detects footsteps.  At has an adjustable sensitivity . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/11/06]


Front End + Power Supply Circuits of the Electric Filed Disturbance Monitor  -  This schematic is the power supply and front-end sections of my field monitor, "Electric Field Disturbance Monitor". The system can detect human and animal motion by the electric fields they disturb . . . [Hobby Circuit designed by David Johnson P.E.,  03/26/02]


Hand Wave motion detector  -  The circuit below works quite well in typical indoor room lighting.  I would not recommend its use in direct sunlight.  Two small PIN photodiodes positioned about one inch apart form a shadow detector.  With no shadow cast on the devices, both devices produce nearly identical current levels . . . [Circuit Solution by Dave Johnson P.E.,  08/21/05]


Home Made Geophone Detects Foot Steps  -  A home made geophone is made from a strong magnet, a coil of wire and a rubber band. The circuit is sensitive enough to detect the vibrations of a nearby foot stomp.  It could be used as an earthquake detector. . . . [Hobby Circuit designed by David Johnson P.E.,  06/02/06]


Human Footstep Alarm  -  This circuit processes the Amplified signals from the footstep detector circuit and activates a microprocessor when the circuit detects footsteps.  At has an adjustable sensitivity . . . [Circuit by Dave Johnson P.E.,  07/11/06]


Human Traffic Footstep Detector Preamp  -  This circuit uses a surplus geophone to detect human footsteps from 100 feet away.  It was designed for monitoring the Mexico/USA border.  This preamp part of the system draws about 50 micro Amps from a 12 volt supply . . . [Circuit by David A. Johnson P.E.,  07/11/06]


Light/Dark Activated Motion Detector  -  This circuit can sound an alarm when the shadow of a hand or arm moves over  two small photo diodes . . . [Circuit by David Johnson P.E.,  08/21/05]


Make a Geophone to Detect Foot Steps  -  A home made geophone is made from a strong magnet, a coil of wire and a rubber band. The circuit is sensitive enough to detect the vibrations of a nearby foot stomp.  It could be used as an earthquake detector. . . . [Circuit by Dave Johnson P.E.,  06/02/06]


Scare Off Pigeons  -  I have an area on my roof where a large flock of pigeons like to roost.  Their nesting materials and droppings really make a mess. Often there is enough junk from them that it clogs my roof gutters.  Perhaps one way to scare them away . . . [Hobby Circuit designed by David Johnson P.E.,  04/01/05]


Shadow Activated Motion Detector  -  The hobby circuit below works quite well in typical indoor room lighting.  I would not recommend its use in direct sunlight.  Two small PIN photodiodes positioned about one inch apart form a shadow detector.  With no shadow cast on the devices, both device . . . [Hobby Circuit designed by David Johnson P.E.,  08/21/05]


Ultra Low Power Human Finger Detector  -  The circuit below seems to work well and averages a current drain of only 10 microamps from a lithium cell.  It uses a single CA4013 dual D flip/flop.  One section is wired as a pulse generator.  It applies 10us 10ma pulses to a LED inside a slotted optical sensor at a rate of about 50Hz.  The phototransistor in the second half of the sensor detects the pulses and sends a pulse to the data input of the second flip/flop in the 4013 package.  If there is nothing between the LED and the phototransistor, the inverting output of the 4013 remains low. . . . [Circuit Solution by David Johnson P.E.,  05/03/06]

 


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