|Street No 333, New Town. With energy|
saver on (top) and off (bottom)
The idea of this pilot path breaking project is to switch off one third of street lights until and unless a car passes.
The challenge was to see that a person or a cattle should not trigger on the lights that are supposede to be switched on only when a car passes. So traditional motion sensors, IR sensors or photo-electric and light based sensors were ruled out. Ruled out also was any pressure sensitive trigger because bullock carts, for example, can trigger the mechanism.
So we thought of eddy currents, earth's magnetic field and recalled that the car is made of metal .
The sensor is based on a copper loop and embedded underneath the surface of the road. One at one end of the road on the entry lane, and one on the other lane of the road, again at the entry lane.
When a car enters Street 333, it disturbs the linked terrestrial magnetism linked to the embedded coil and generates an eddy current. This is amplified and used to switch on the till-then-unlit street lights. It switches off after 5 minutes automatically through a timer mechanism, 5 minutes being the average time required for a car to traverse he 1 km length of road no 333.
I saw it in operation yesterday. Working fine.
Street no 333 is between Biswa Bangla Sarani near Bagjola Canal and connects to Major Arterial Road near Alia University/ Amity University.
39 light poles, 80 LED Street Light Assemblies. 52 such light assemblies (read bulbs in simple terms !) connected to sensors. Total estimated cost savings Rs 2 lakhs per year