Motion detector switch in Hidco Bhavan installed: another smart step

I was a bit surprised to see that the lights in my office chamber at Hidco Bhavan were not switched on when I pushed open the door this morning. But as soon as I entered and started going towards my table, the lights came on on their own for one half of the office chamber. When I reached my table, the other half too lit up. I was told that Chief Engineer (Elec) S P Chatterjee had installed these infra red motion detectors yesterday while I was in Delhi. This was based on a discussion taken in one of the recent weekly meetings where I talked of conserving street lights through motion detector devices. Here is a picture of the ceiling mounted device (there are two in two halves of the room):

Motion detector in Hidco
(the round one)

I looked up the web to understand how this works. Here is an excerpt from Howstuffswork:

" The "motion sensing" feature on most lights (and security systems) is a passive system that detects infrared energy. These sensors are therefore known as PIR (passive infrared) detectors or pyroelectricsensors. In order to make a sensor that can detect a human being, you need to make the sensor sensitive to the temperature of a human body. Humans, having a skin temperature of about 93 degrees F, radiate infrared energy with a wavelength between 9 and 10 micrometers. Therefore, the sensors are typically sensitive in the range of 8 to 12 micrometers.

The devices themselves are simple electronic components not unlike a photosensor. The infrared light bumps electrons off a substrate, and these electrons can be detected and amplified into a signal.

You have probably noticed that your light is sensitive to motion, but not to a person who is standing still. That's because the electronics package attached to the sensor is looking for a fairly rapid change in the amount of infrared energy it is seeing. When a person walks by, the amount of infrared energy in the field of view changes rapidly and is easily detected "

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Today Finance Minister Amit Mitra, Chief Secretary Sanjay Mitra, ACS(Commerce) C M Bachhawat, ACS(Power) Gopalkrishna, Pr Secretary (Health) Malay De, Pr Secretary (IT) Satish Tewari, Pr Secretary (Finance) H K Dwivedi, Pr Secretary (MSME) Rajiv Sinha, MD WBIDC Krishna Gupta and others visited Eco Pak in the morning and held a meeting in Glass House. This was a follo-up meet of the industry-diplomat meeting of Hon'ble Chief Minister held on 11th Sep.
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A new bank branch opened at Hidco Bhavan compound today. This is a result of sustained efforts of CFO Samaresh Mitra. An earlier security building was converted into a two storied building and modifications made to make the ground floor suitable for banking. The ATM counter will soon be opened. A photo (courtesy Subhashis Gupta):

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Two clippings:

Ei Samay dt 12.9.2014

Times of India dt 12.9.2014