Inductive loop traffic detector | McLarenChat

Inductive loop traffic detector

Discussion in 'McLaren Discussion (Not Model Specific)' started by vincep99, Mar 19, 2020.

  1. vincep99

    vincep99 Rookie

    Jun 8, 2009
    Here's a question to start some discussion: will these traffic detectors used to turn traffic signals green be less effective on our Mclarens due to the extensive use of CF?

    I assume there is still enough metal mass so the light will trigger OK.

    I know that many won't detect motorcycles.
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  3. JOEA2

    JOEA2 Karting
    Premium Subscribed

    Feb 2, 2006
    Staten Island, N.Y./ Sea Girt,N.J.
    Full Name:
    Joe A
    I haven't had a problem. If they make the Engine out of CF, we could be in trouble.

  4. Booker

    Booker Formula Junior
    Miami 2018

    Aug 1, 2016
    Dallas, Tx
    Full Name:
    Jack Booker
    Can you explain how these work and how it relates to mass? I assumed lower profile cars with odd shapes would be harder to detect, but I do not understand the technology
  5. Ingenere

    Ingenere Formula Junior

    Dec 11, 2001
    On the Limit
    Full Name:
    I would like to know the story with this as well.
  6. vincep99

    vincep99 Rookie

    Jun 8, 2009
    I am not an EE, so I looked it up:
    Vehicle detection loops, called inductive-loop traffic detectors, can detect vehicles passing or arriving at a certain point, for instance approaching a traffic light or in motorway traffic. An insulated, electrically conducting loop is installed in the pavement. The electronics unit applies alternating current electrical energy onto the wire loops at frequencies between 10 kHz to 200 kHz, depending on the model. The inductive-loop system behaves as a tuned electrical circuit in which the loop wire and lead-in cable are the inductive elements. When a vehicle passes over the loop or is stopped within the loop, some of the vehicle's ferrous body material increases the loop's inductance, in the same principle as including a metal core within a solenoid coil. However, the peripheral metal of the vehicle has an opposite effect on the inductance due to eddy currents that are produced. The decrease in inductance from the eddy currents more than offsets the increase from the ferrous mass of the engine, and the net effect is an overall reduction in the inductance of the wire loop. The decrease in inductance tends to decrease the electrical impedance of the wire to alternating current. The decrease in impedance actuates the electronics unit output relay or solid-state optically isolated output, which sends a pulse to the traffic signal controller signifying the passage or presence of a vehicle.[4] Parking structures for automobiles may use inductive loops to track traffic (occupancy) in and out or may be used by access gates or ticketing systems to detect vehicles while others use parking guidance and information systems. Railways may use an induction loop to detect the passage of trains past a given point, as an electronic treadle.

    The relatively crude nature of the loop's structure means that only metal masses above a certain size are capable of triggering the relay. This is good in that the loop does not thus produce very many "false positive" triggers (say, for example, by a pedestrian crossing the loop with a pocket full of loose metal change) but it sometimes also means that bicycles, scooters, and motorcycles stopped at such intersections may never be detected by them (and therefore risk being ignored by the switch/signal). Most loops can be adjusted manually to consistently detect the presence of scooters and motorcycles at the least.
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  8. slm

    slm Rookie
    Premium Subscribed Owner

    Dec 5, 2004
    Ozark Americana
    Full Name:
    Steve M
    Interesting. We have a gate at the end of our driveway. The exit sensor does not detect our golf cart or the McLaren.

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