Smart Street Lighting Using Embedded Systems

Vedant Prusty (Mechatronics), Rishabh ESP (ECE), Sarthak Prakash (Mechatronics)

Manipal Institute of Technology, Manipal

Abstract:

The 21st century has seen astounding growth in the consumption of electricity or energy from fossil fuels. A significant portion of this electricity gets consumed in thousands of miles of street lighting in highways all over the world. With road construction being paced up, especially in developing countries, there is a need to develop and implement a cost effective solution to the huge power consumption in street lighting.This project proposes a smart street lighting system (STRIGHT), as a marketable ready-made product, which can be directly installed on street lamps already in place. Keeping minimal cost of installation in mind, Stright based on a microcontroller, along with sensors and wireless communication offers a cost effective model to save energy in streets lighting without compromising on safety.

The Idea:

Stright must be able to conserve electricity by switching off when there is ample ambient light or when the road is not being used. It will also be able to control the orientation of a small solar panel attached to the head of the lamp post, for harnessing solar energy optimally. Besides this, Stright has an integrated road usage detection mechanism. By using Ambient Lighting Sensors which have proximity sensors integrated in them, it will be able to detect vehicles or persons passing by, and hence increasing light brightness or switching on completely. A Bluetooth communication model allows it to communicate serially with nearby lamp posts warning them of passing objects on the road, and relaying switch-on or off instructions. Each of the features on the device will be made optional by using Modes, which the operator can select. Once installed, all operation is automated. Safety is kept a priority to ensure no accidents due to a system error in detecting ambient light, objects on the road, receiving relayed information, and calculating switch-on time for the lamp.

Stright will be designed as a directly installable product, which can be used as an add-on to the infrastructure already present. It will be connected in the main live line going on the lamp, in series. Voltage dividers and transformers will step down the voltage to necessary levels for use by the

embedded system. BY controlling amount of current passing through the filament, the brightness of lamp can be controlled.

Each of the features of Stright has been explained in detail below:

Solar Panel Directing Mechanism:

As an optional feature, a solar panel supported on a stepper motor may be installed on the lamp post along with Stright. In such a case, Stright will ensure that the solar panel is optimally inclined and directed towards the sun, in order to receive maximum energy from perpendicular sun rays. Stright will control the stepper motor based on input signals from a sensor.

p.s. the energy from the solar panel may be stored into a battery, or siphoned back to a power grid. Power Management of energy gained from the Panel is not a subject of this design. Sright only offers the optional feature of having an integrated system to optimize energy harvesting.

Installation in Series on Live Cable:

Stright will be installed by cutting a section on the live line going to the lamp, in series. Voltage dividers or transformers will step down the voltage to the required levels for use by sensors, and various modules in Stright. Stright will also contain the amount of current passing through to the lamp. This of course will be an optional feature, and will be able to control light intensity wherever applicable (the type of lamp being used must be considered). Intensity of current passing though may be controlled by a BJT whose gate voltage is controlled by the Microcontroller.

Excess current may be siphoned off through heat sinks, or in the presence of a battery as explained above, used to recharge the battery.

Ambient Lighting Sensor

An ambient light sensor will be able to convert ambient light analog values to digital values, and feed them directly to the main Microcontroller. The microcontroller then decides to control the light intensity or on/off status accordingly. A threshold may be set for light-on condition after ambient light reduces below a certain level.

Threshold Model: Switches light on or off based on ambient light. Open Loop System.

Continuous model: Maintains a certain level of ambient light by controlling light intensity of lamp. Switches off in presence of full sunlight. Closed Loop System.

Vehicle/Person detection and triggering

The Ambient Light Sensing module consists of an IR Sensor as well. It emits and IR beam towards the road, and is able to detect reflected IR rays from various moving objects by using a Photo LED. In the presence of and object, the module triggers the microcontroller by generating an interrupt and the lamp is lit accordingly. Once the object is out of range, the lamp swatches off automatically after a pre-determined “safe time”.

Bluetooth Communication

Stright consists of a Bluetooth module used to communicate with modules installed on adjacent lamps. Each lamp communicates only with two adjacent lamps (assuming a single row of street lamps on one side of the road). As soon as the IR sensor detects a moving object, and the microcontroller is notified, a message is broadcast to two adjacent Stright systems.

It is important that this system be integrated with the above IR sensing system. As a safety feature, the lamp will turn on anyway when it detects an object in front of it, irrespective of Bluetooth signals. However, to facilitate a larger lit-up area for a vehicle or person, three lamps closest to the person are always kept lit by this communication model, which is open to customization.

Device ID and identification by Time of ArrivalEven though each of the Stright modules on the road will act as a node with a unique Device ID, the communication protocol will not depend on this solely. This removes the need to program each module to identify the names of the two adjacent modules. Code is made lighter, and in the event of failure of a single node in the row of lamps, the overall module does not fail (as the next closes lamp will be automatically considered the adjacent node) This foolproof model will analyze the Time of Arrival of signals to identify closest nodes, and respond to only the two signals with shortest times.

Fault Tolerance and Safety Features in Stright:

Dual wake up system for lighting- IR sensor as well as wireless communication, both trigger the lamp to switch on. Stright will work even when one of the systems fails.

The switching-on time for each lamp can be programmed into the system based on the type of lamp being used. This ensures optimum time for triggering power, and prevents possible accidents.

Life Cycle of the lamp can be increased. By analyzing in Real-time the traffic flow, lamp can be kept switched on for longer periods instead of intermittent on-off, which tends to reduce lamp light significantly.

Use of Wake-up System, Sleep mode, and Pico Power Technology:

Stright keeps energy conservation a priority. By using the built in Pico-Power Technology already available in the Atmel Module, Stright will remain in a sleep/low-power state by default. In the event of a trigger or interrupt generated through the incoming of wireless signals from adjacent lamp posts or nodes, OR, if the IR sensor activates, Stright will be stimulated to wake up and analyze these signals to switch on the lamp if needed. This will ensure that the system does not remain in continuous-on mode. The use of Pico-Power technology’s short wake-up time, with multiple wake-up sources from even the deepest sleep modes is sure to leave Stright as a customized, efficient, and easily implementable solution.