So just something that’s been on my mind. At my workplace there’s an automatic road barrier that lifts up and down when vehicles arrive. However, it’s not used for a carpark system when people wave their tickets or something. It just goes up and down when a vehicle shows up.

However, it sometimes goes up for when say a pushcart is being rolled over whereas it wouldn’t for a guy pushing a bin.

So tldr, how does an automatic road barrier decide that yes, a vehicle is coming, and therefore opens up?

  • @[email protected]
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    468 months ago

    Same as traffic lights. “Inductive-loop traffic detectors use an electrically conducting loop embedded in the pavement to send a signal to the traffic control system to indicate the presence of a vehicle.”

    • Otter
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      468 months ago

      So a large wooden horse could slip by without detection

      • astraeus
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        168 months ago

        If the large wooden horse is full of men in metal armor, purely hypothetically speaking, would the loop still not pick up the large wooden horse?

        • wkk
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          88 months ago

          Technically speaking it would pick up the men in metal armors, not the wooden horse per se.

          But the barrier would lift for the wooden horse full of men in armor indeed.

          • _haha_oh_wow_
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            48 months ago

            Depends on how high on their horse they are: They might be too far away to trigger the sensor.

    • @[email protected]
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      8 months ago

      This, it’s like a metal detector but, bigger. Temporary boom gates might use infrared motion sensors like automatic lights. edit: “lights” like the lights some people have on their porch.

      • TWeaK
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        58 months ago

        It’s bigger in overall structure size, but isn’t really that big itself. It’s just a wire loop, they can be installed into existing roads with minimal effort - they just dig a narrow trench and then seal it up, it doesn’t require more tarmac.

    • @tired_lemmingOP
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      48 months ago

      Huh, so that’s a completely new concept I’ve learned today. Time to do more reading. Thanks!

      • @[email protected]
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        48 months ago

        Check the road in front of the gate. Those loops are usually installed after the asphalt so there should be a loop patched up with tar a bit smaller than a footprint of an average car.

  • @[email protected]
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    68 months ago

    There could be a motion sensor behind maybe? It could be one of those places that have a bunch of coils on the ground, wherein a large enough mass of metal gets detected by changing magnetic or electric fields, or something else entirely

  • FuglyDuck
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    48 months ago

    Could be a lot of ways- an IR beam some where before the barrier. A motion sensor (usually IR or IR+ultrasound). Possibly some sort of movement detection on the security cameras.

    Or a magnetic loop sensor, which is my guess. (You’d see the other sensors.)