Question

what's in the traffic light ?

how it works?

digitally.

Answer 1

Every traffic light signal has either a timer or sensor which helps it direct traffic flow. In large cities where vehicles cross road intersections across the clock, traffic is usually dictated by traffic lights that use timers.

But in the suburbs and up county roads, traffic signal sensors (detectors) are usually preferred because they not only manage the inconsistent traffic flow effectively, but also detect when cars arrive at intersections, when several cars are stacked at an intersection and when cars have entered turn lanes.

These sensors use different technologies, from induction loops, microwave radar, cameras, lasers to rubber hoses filled with air.

Induction Loops

The primary, reliable and most common traffic light sensors are induction loops. Inductive loops are coils of wire that have been embedded on the surface of the road to detect changes in inductance and convey them to the sensor circuitry in order to produce signals.

The loop is usually fed with a given frequency from a generator, resulting in an induced magnetic field. And as the magnetic field continues to build due to continuous flow of current, the coils will achieve a stronger field that can last for a period of time even after the switch is opened.

For an induction loop to achieve greater inductance and be more reliable in traffic detection, it should have several wire coils and an iron (magnetic material) core. The core is the material on which the wire coils are wrapped.

When coils have been placed in the grooves and covered with rubbery compounds, they produce a specific quantity of inductance which can be measured using an inductance meter.
But when a car stops on or drives over the loop, the larger steel (metallic) material making up the body of the car will act as the core of the induction loop. Since steel is a magnetic material, it will increase the inductance of the loop and cause a change in the current flowing through the sensor circuitry.

Therefore, when the changes in the magnetic field are conveyed to the signal controller by the wire coils, they cause a change in traffic signal.

Induction loops offer several advantages. They are not affected by the weather and are quite immune to accidental false positives.

They can also cover lengthy parts of the lanes and can be localised according to user needs.
Nevertheless, they may fail to detect bicycle traffic because of the little metallic component of bicycles.