Symbiotic Camera Cadges Power from Fluorescent Light
While the nature of the mounting mitigates any real ability to perform as "spy camera," the ring that slips around a fluorescent light bulb to harness the magnetic field generated by the light's normal operation is powerful enough to power both the camera and the Wi-Fi chip inside. The VGA-resolution camera, made by NEC, can snap images every 10 seconds, beaming them back to a PC.
If the ring doesn't cause any additional power to be drawn in the operation of the lamps—and using my rudimentary grasp of light bulbs I don't see how it would—then it's a very clever way to harness cast off electricity, even if it's only 120 milliwatts.
NEC spy camera draws its power from fluorescent light tubes [DigitalWorldTokyo.com]
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It's more accurately parasitic rather than symbiotic. It provides no benefit to the lamp.
You know, I chewed on that for a while before choosing "symbiotic," but it's not strictly parasitic either, if the power is already being wasted. (Are plants parasitic if they process spent CO2?) Surely there is a third term for things that are neither harmful nor beneficial.
The lamp is not using "cast off" or "wasted" energy. It is increasing the power drawn by the lamp in order to power the camera. The ring around the lamp electromagnetically couples the camera to the lamp and increases the electrical load of the lamp. The higher load increases the current draw of the lamp. It's clever, but it's just avoiding the need for a separate power cord, not getting power from nowhere.
Epiphytic perhaps.
But I'm suspicious that this doesn't cause increased inductive resistance or somesuch that results in more power being drawn by the lamp. (Not that I know anything about how fluorescent lights work...)
This is how I understand it. It would decrease the impedance and thus increase the electrical load.
When you have an inductor (in this case the fluorescent bulb) the impedance comes from the electromagnetic field opposing the changing current. The coil in the ring that goes over the bulb turns it into a transformer. Some of the energy in the electromagnetic field goes towards making current flow in the coil, and so less energy is available to opposing the current flow in the bulb, thus decreasing impedance and increasing the number of watts drawn.
Post 5 by anonymous is exactly how I understand it as well. The camera's coil is effectively in parallel with the bulb. The resulting impedance is computed as (R1 X R2)/(R1 + R2), assuming zero phase angle, which it isn't but it's a close approximation.
Epiphytes merely use another entity for support. My wristwatch is epiphytic. Come to think of it, it's an auto-winder so it's also parasitic, using the motion of my arm to wind its mainspring. I never thought of it that way before.
The coil is increasing the impedance of the lamp, causing a slight dimming. The coil affects the flow of electrons through the lamp. Think of it as a transformer with the lamp current being a single turn primary and the coil a multi turn secondary.
BTW it only works with electronic (not magnetic) ballasts. Most offices have electronic ballasts.
I'll be the first to say awesome lamp, parasitic/symbiotic debate aside.
Obviously I exceeded my grasp of both electronics and English. Thanks for learnin' me so good, guys!
Of course it's a symbiotic relationship: for the sacrifice of a modest increase in effort the lamp receives the protection of the camera by way of a deterrent to bulb thieves. It's exactly analogous to the relationship between swollen thorn acacias and acacia ants.
And I would say, awesome parasitic/symbiotic debate, lamp aside.