Choosing the Right Sensor Type
Before deciding on the right product, or even the right type of sensor, first ask yourself what are you trying to monitor? Do you want to know when cars only enter or pass through the monitored zone? Do you want to know if ANYTHING, including people, pass through the zone? Answering these question will help you understand what type of sensor you are going to need to do the job you want.
I only want to detect automobiles
There are two types of sensor carried at Sensor City that will allow you to DETECT CARS & TRUCKS ONLY and those are “pneumatic” and “magnetometer” based sensors. These types of sensor work in completely different ways and for different reasons will detect metallic and/or heavy objects only.
Pneumatic Based Sensors
“Pneumatic” means “using air pressure to move or work” (http://www.merriam-webster.com/dictionary/pneumatic), In the context of driveway alarms, pneumatic sensors work when a car or truck rolls over a rubber hose. As the heavy object rolls over the rubber tubing, the sudden change of air pressure causes the sensor to trigger.
In most cases, these sensors will not trigger simply by the weight of a person stepping or walking over the tube (jumping on it could trigger it). Most often, a rubber hose it laid across a driveway or entrance. As a car rolls over the tune, the sensor triggers a bell sound.
Think of old school gas stations or even dry-cleaning establishments. The small drive-thru lane is perfect for laying a runner hose across it.
Magnetometer Based Sensors
A Magnetometer is an “instrument used to detect the presence of a metallic object or to measure the intensity of a magnetic field” (http://www.merriam-webster.com/dictionary/magnetometer) and are great, in the driveway alarm world when you want to monitor heavy metallic objects (think car or truck) passing through a monitored zone.
Typically, driveway alarm kits with a magnetometer sensor contain a probe. This probe is the magnetometer and it’s typically buried under the driveway or parallel to the driveway. Any heavy metallic object passing near the probe will disrupt the measured magnetic field as measured by the probe. When a disruption is detected, the circuit is closed and thus, the sensor is triggered.
These types of sensors are perfect when you only care about detecting cars or trucks that enter your driveway (or monitored zone). If you live in a heavily wooded area, or an area where animals could cause false alarms, these types of sensors may make sense for you.
I Want to Know when Anythingt enters my driveway
Passive Infrared Motion Sensors (PIR)
Passive Infrared Motion Sensors (PIR) are the most commonly used sensor type in alarm and security systems. A PIR sensor detects changes in infrared heat which is generated when objects move in front of it. When this change in infrared radiation is detected, the sensor is triggered, thus transmitting a radio signal to the receiver.
These sensor are going to trigger when a person, car, truck, or animal passes through the detection zone.In many products, you can adjust the sensitivity of the sensor or change the angle of the detection zone to limit any “false alarms” and they do a pretty good job at doing that.
Break Beam Sensors
Break beam sensors work when the beam sent from the emitting sensor to the receiving sensor is broken. This broken beam triggers the sensor to transmit a radio signal to the receiver.
These products have come a long way since the days of science calls when a visible light wave was used. The sensor used on our kits use IR Infrared Light. The sending unit sends a IR beam of invisible light to a receiver that is sensitive to that specific wavelength. When it stops receiving that wavelength of light, ie., something passes through the monitored zone, the sensor is triggered to send a radio signal to the receiver.
These sensor are going to pick up ANYTHING that breaks the beam. The great thing about these products is you can pair multiple sensors together to set up more of a perimeter, or simply set up one pair.
An advantage of using these types of sensor is that you won’t have to worry as much about the monitored zone bleeding or straying out into another area.