Traffic light

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domnic

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Would a totally aluminum car trip a traffic light ( induction type ) ?
 
domnic said:
Would a totally aluminum car trip a traffic light ( induction type ) ?
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In general, yes. The presence of a lump of conductive metal, even if not ferrous, will change the Q of the loop and will be detectable by current hardware even if the change to the loop inductance is small.
Very early loop detectors may be looking for a change in inductance only and those would not respond.
 
domnic said:
Would a totally aluminum car trip a traffic light ( induction type ) ?
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Is this a hypothetical question or a problem you are having?

Is there such as thing as a "totally" aluminum car? NO steel in it ANYWHERE? Body, sure, in fact there are fiberglass car bodies too. Frame, maybe. Engine? Radiator?

But to answer your question directly, it doesn't matter if it is aluminum, only that it is conductive, and aluminum is conductive. A traffic loop detector creates a magnetic field, which induces a small current flow in the metal object, which in turn interferes with the magnetic field in the loop, which is what is detected. So any conductive material entering the loop interacts with it and triggers the sensor. HOW MUCH metal it takes is a matter of the sensitivity adjustments, so they try to make sure for example that the loop detects a bicycle rim, but not a big shiny silver belt buckle on a pedestrian's jeans.
 
Jraef said:
... so they try to make sure for example that the loop detects a bicycle rim, but not a big shiny silver belt buckle on a pedestrian's jeans.
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Along those lines, to better detect metal close to center of the loop without causing too high a sensitivity to what is in adjacent lanes, detector loops that need to reliably detect bicycles are wound as magnetic quadrupoles (figure 8 loop) instead of dipoles (traditional single loop).

Quadrupoles also have the advantage of being most sensitive to low lying metal at their center line while dipole loops are more sensitive at their edges.
With dipole loops I can get better detection by laying my bike down on its side to put a larger conductive loop (frame) closer to the sensing loop.
 
Back when I rode a motorcycle, I had little patience for stoplights. After coming to a stop on the loop, I would kill the engine. I would immediately start the engine with the electric starter in the belief that a field coming from the starter would trigger the loop.
 
There are no totally aluminum cars. The crankshaft, flywheel, cam/valvetrain, timing chain, bolts (all hardware), brake rotors, transmission gears/shafts and cv/driveshafts are steel no matter how exotic a car you buy; several hundred pounds of steel.
 
jeremysterling said:
Back when I rode a motorcycle, I had little patience for stoplights. After coming to a stop on the loop, I would kill the engine. I would immediately start the engine with the electric starter in the belief that a field coming from the starter would trigger the loop.
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well, most of the bike is aluminum, any more.
and not a lot of it. usually won't be enough mass
to trigger the road loop......

i never thought of turning off and on the engine
to trigger it. i usually just looked around, then
proceeded thru the intersection. seemed to work
ok.
 
A lot of detection is moving away from loops. The standard loop is 3 loops of wire around a square cut. Next is a 3 loops in 3 cuts giving 6 wires in center ( for motorcycles). In newer installs the use of cameras is preferred for both cars and new bike lanes.


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ggunn said:
So they can write tix for running red lights without having to have a cop on site. :D
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The cameras used for vehicle detection are generally not suitable for license plate reading and red light monitoring.
A multi camera system that does both is certainly possible though.
 
ggunn said:
So they can write tix for running red lights without having to have a cop on site. :D
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No cameras on the red light wire or arms only read where cars are on the road. Red light cameras are privately owned and not on state or city poles.


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That is an over generalization. Enforcement (fines) for red light cameras is often contacted out to a company that takes a percentage of the money collected, but at least some of the cameras are municipally owned and maintained.
 
JFletcher said:
There are no totally aluminum cars. The crankshaft, flywheel, cam/valvetrain, timing chain, bolts (all hardware), brake rotors, transmission gears/shafts and cv/driveshafts are steel no matter how exotic a car you buy; several hundred pounds of steel.
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We're getting close...

The Audi Q8 e-tron won't have a crankshaft, flywheel, cam/valvetrain (nor internal combustion anything), timing chain (which a lot of cars have belts anyway), brake rotors (a lot have ceramic compounds), typical transmission....and the drivetrain will be motor on wheel.

Very cool stuff.

The seatbelt clips are steel, though...

If a bike wouldn't trip the light, these might not either.
 
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