| Contest Pictures | |
 | | THE WINNER |
 | | NEW EXTERIOR-by Chadwick, March 29th |
 | | Brand new 64 circuit - 100 Amp Seimens panel for the O'Brien family |
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| Occupancy Sensors | |
- Occupancy sensors automatically turn the lights on as soon as they detect occupancy.
- When a time delay has been reached without further occupancy being detected, they turn the lights off. If desired, occupancy sensors may be manually overridden to keep lighting off or on, as needed.
- These sensors can easily replace a standard lights switch, and there are ceiling mount units that are particularly useful in washroom applications.
The two most common technologies for sensing motion use infrared LED or ultrasonic sound waves. |
| PIR sensors -how they work | |
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Passive infrared (PIR) sensors react to the infrared heat energy emitted by people. They are designed to be maximally sensitive to objects that emit heat energy at a wavelength of around 10 microns (the peak wavelength of the heat energy emitted by humans). PIR sensors are strictly line-of-sight devices. They cannot "see" around corners or through partitions. |
| Ultrasonic sensors - how they work | |
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Ultrasonic occupant sensors activate a quartz crystal that emits ultrasonic waves throughout the space. The unit then senses the frequency of the reflected waves. If there is motion, the reflected wave's frequency will shift slightly. These too, are line of sight devices, but can sometimes respond to emitted sound waves around partitions. |
| Comparing the two | |
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Passive infrared and ultrasonic occupant sensors offer very similar characteristics in terms of overall performance.
- Ultrasonic sensors are more expensive, as a rule, but provide greater coverage than PIR detectors but are more susceptible to false triggering due to any movement in the space. Unless carefully calibrated, ultrasonic sensors will react to non-occupant movement such as breezes from open windows and heating and A/C systems.
- PIR technology is the better choice for outdoor use making them excellent for treed areas or on waterfronts where the wind causes motion that creates false ons. Good quality PIR sensors can be set so geese, cats and racoons won't set it off as they won't be the ones bothered by the light anyway.
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| Ask the Doc | |
Dear Doc, My porch light is a motion sensor. Sometimes I get woken up when when it comes on but no one is ever there. What's up?
Dear What's Up, I suspect you have an economy model motion sensor that relies on old technology that causes false tripping and wasted energy. Also the electronics are susceptible to power surge damage so it may be defective. Sensing lights are alot like whiskey - the more expensive the product, the better it is. To aleviate your problem, the best solution is to buy a good quality PIR technology motion sensor. If you cannot find a good one, call us, we will be happy to help you out. |
| Do you have a question for the Doctor? | |
 If you have a question about the health of your electrical system or would like to investigate a little "plastic surgery", Ask the Doc himself! Click and send your question to terry@theshockdoctors.ca.
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Congratulations to the OBrien family!
Cheri 
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