Detecting Motion
Posted by delaney1019 | Filed under Uncategorized
Circuit alarms are very effective for guarding the perimeter of a house, but they don’t work so well inside a building. This is because the intruder’s actions are highly unpredictable, you don’t know where they’ll go or what they’ll touch. A specific “trigger” isn’t very effective. To detect an intruder who’s already in the house, you need a motion detector. Basic motion detectors are fairly common these days. You see them all the time in automatic doors, for example. There are several different sorts of detectors. An automatic door opener is an example of a radar-based motion detector. The box above the door sends out bursts of microwave radio energy (or ultrasonic sound waves), and then waits for the reflected energy to bounce back. If there is nobody in front of the door, the radio energy will bounce back in the same pattern. But if somebody enters the area, the reflection pattern is disturbed. When this happens, the sensor sends a signal and the door opens. In a security system, the sensor sends an alarm signal when the reflection pattern in a room is disturbed.
One Response
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Kelly Brown Says:
June 12th, 2009 9:20 pmHi, very nice post. I have been wonder’n bout this issue,so thanks for posting
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