Red Light Camera activation?

[Davi]

Just wondering at what point do Red Light camera's activate, do you have to cross a certain line after they turn red?

This morning I was approaching a traffic light as it turned orange. I was way too close to stop safely without gaining the tailing Isuzu as a boot ornamant, so continued through. The lights went to red when I was about half way through.

wouldn't normally have worried as I know I did the right thing, but I saw something flash in the mirrors - it may just have been the headlights of the car that turned in behind but with all these automated devices you never feel quite sure!

[Flat in Fifth]

It really depends where the sensor loops are, look for the narrow shiny lines where slots have been cut to bury the cables and then filled in with the mastic / tar or whatever substance used to fill in the repair.

[Davi]

Flat in Fifth said:

It really depends where the sensor loops are, look for the narrow shiny lines where slots have been cut to bury the cables and then filled in with the mastic / tar or whatever substance used to fill in the repair.

Thanks FiF just what I needed, I'll have a peek on the way in tomorrow.

[mattyboy101]

IIRC, they have an induction loop (I believe) just before the line and then another shortly after it, if the front of your vehicle is over the first loop when the lights go red I believe you are ok.

[madleee]

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

[havoc]

madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

Have they made an engine block out of anything other than metal yet?!?

[smeggy]

havoc said:

madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

Have they made an engine block out of anything other than metal yet?!?

The Flintstonemobile

[Flat in Fifth]

havoc said:

Have they made an engine block out of anything other than metal yet?!?

but madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

:cough:

[smeggy]

Flat in Fifth said:

havoc said:

Have they made an engine block out of anything other than metal yet?!?

but madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

:cough:

Any metal will register at an induction loop, ferrous or not. How do you think copper wire wound transformers work?

[havoc]

smeggy said:

Flat in Fifth said:

havoc said:

Have they made an engine block out of anything other than metal yet?!?

but madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

:cough:

Any metal will register at an induction loop, ferrous or not. How do you think copper wire wound transformers work?

Oh FiF...

:cough:

[andmole]

smeggy said:

Flat in Fifth said:

havoc said:

Have they made an engine block out of anything other than metal yet?!?

but madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

:cough:

Any metal will register at an induction loop, ferrous or not. How do you think copper wire wound transformers work?

Copper wire wound transformers only work with a soft IRON core.

[smeggy]

andmole said:

Copper wire wound transformers only work with a soft IRON core.

A core isn't needed at all (although it does help of course).
A soft core aids conduction of magnetic flux around a circuit, not relevant to induction loops.

Before anyone else argues - I just tried it - with an air wound copper coil, a 100% aluminium block (confirmed non-ferrous with use of very large grade N50 neodymium magnets) and a high frequency AC voltage. The current through the coil doubled as the aluminium block was brought near.

Let that be the end of it

[mattyboy101]

Davi said:

Just wondering at what point do Red Light camera's activate, do you have to cross a certain line after they turn red?

smeggy said:

A soft core aids conduction of magnetic flux around a circuit, not relevant to induction loops.

[Flat in Fifth]

smeggy said:

Flat in Fifth said:

havoc said:

Have they made an engine block out of anything other than metal yet?!?

but madleee said:

Theoretically, if I had a non ferrous or totally plastic car, would I avoid the induction loops in the road?

:cough:

Any metal will register at an induction loop, ferrous or not. How do you think copper wire wound transformers work?

No but the point is that, as andmole says, soft iron is used in transformers because it has a much higher permeability. Other material eg non ferrous metals could be used but because of their lower permeability are not.

The situation with road detection induction loops is that they rely on the mass of steel from a vehicle to act like the core and change the inductance of the loop.

However it is quite possible that a small aluminium vehicle, for example a motor cycle might not change the inductance of the loop sufficienntly to be detected. Not just theory has been observed in practice.

So right back at you.

[smeggy]

It is also possible for ferrous materials not register on induction loops - if the ferrous component and the conductive mutual inductance are in equal balance.

I hope that we can all agree that, in principle, ferrous and non-ferrous metals can be detected by induction loops!

[Flat in Fifth]

smeggy said:

I hope that we can all agree that, in principle, ferrous and non-ferrous metals can be detected by induction loops!

Oh agreed, the key factor is the calibration of the sensor equipment.

Thinking back, didn't the very early Audi A8 have some parts deliberately made of ferrous material because they were not being detected by induction loop sensors?

Anyway if we look back we can see it's all havoc's fault for making the totally erroneous point about engines and metal when madleee had asked about non ferrous etc. Then we've gone off at a tangent as usual.

[havoc]

Flat in Fifth said:

Anyway if we look back we can see it's all havoc's fault for making the totally erroneous point about engines and metal when madleee had asked about non ferrous etc. Then we've gone off at a tangent as usual.

It's a fair cop guv'nor!