Security-door-ajar-alarm


Posted on Apr 5, 2012

In operation, the TL3019 device will activate, or become low, when a south pole of a magnet comes near the chip face of the device. The example shows five doors. Each door has a magnet embedded in its edge with the south pole facing the outer surface. At the point where the magnet is positioned with the door closed, a TL3019 sensor is placed in the door jamb. With the door closed, the Hall devices will be in a logic low state.


Security-door-ajar-alarm
Click here to download the full size of the above Circuit.

This design has five doors and uses five TL3019 devices. Each TL3019 has a 4-KO resistor in series and all door sensor and resistor sets are in parallel and connected to the inverting input of an LM393 comparator. With all doors closed, the effective resistance will be about 800 0-and produce 2.2 V at the inverting input. The noninverting input goes to a voltage divider network which sets the reference voltage. The 1.5-KO potentiometer is adjusted so the indicator goes out with all doors closed. This will cause 2.35 V to appear at the noninverting input of the comparator. When a door opens, the voltage at the inverting input will go to 2.5 V which is greater than VRm and the LED will light. A large number of doors and windows can be monitored with this type of circuit. Also, it could be expanded to add an audible alarm in addition to the visual LED.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Simple GAL Programmer
10 Led Chaser
100W DC Inverter Circuit with PCB Design
arduino Switch transistor with a low voltage and current
Amplifier Schematic
Positive voltage to negative voltage converter
Nicad Battery Charger
Single-Chip VHF RF Preamp
Tilt Sensor via Accelerometer Circuit
Infrared IR Receiver Circuit
G3XTZ DF Rx Details
Suppressor circuit diagram for singing karaoke
OPA37 low-noise preamplifier
Breaker control signal circuit manually
Using tap potentiometer loudness circuit



Top