Traffic light changers: and a free gift to New Plymouth peoples

[firefighter]

Late at night, I sometimes ignore the lights (particularly red turn arrows) if there's no traffic - just pause, look around, and go.
Think about it: traffic lights are supposed to replace road signs and people making decisions based on road rules, traffic, etc. They should make traffic flow better and more safely. If they're being stupid, and actually hindering traffic flow, what's the point of them?

in the U.S it's legal to turn right on a red, you give way but if it's clear you go (obviously) which is the same as us going left, which I think is bloody awesome, and we should do the same here.

[Badjelly]

As for current flowing through the loop etc and moving bikes it's not quite like that as far as I'm aware. The loop doesn't need a moving object. An object that suddenly appears will trigger the electronics (although it would be hard to imagine that happening)

The thing in the ground is an inductive loop. So when it's connected to the electronics there is a certain impedance measured (not resistance). The arrival of a vehicle changes the impedance and if it's above a set level the electronics do their thing.

Interesting. To do that there would have to be an alternating current flowing through the loop. A metallic object in the vicinity would then change the impedance of the loop, which would change the amplitude or phase of the AC, which could be detected.

The other way they could work would be passive. A moving magnet (or a moving metal object disturbing the Earth's magnetic field??) would generate a current in the loop. The method would not require any pre-existing current in the loop. But you say this is not the way they work.

Either way a magnet on your bike should improve its detectability, I think.

I don't know that these musings have any practical relevance, but I like to know this stuff. (Just like countersteering, really.) Time for some research...

Edit: Wikipaedia says they work like metal detectors:

http://en.wikipedia.org/wiki/Metal_detector

[ColonelKFC]

I always thought it was a weight related thing. They put temporary lights on Bryants bridge in Aokautere in Palmy when it collapsed and went to one lane. they also put in sensors below the road for a couple of months. Being me, I parked right on top of the bastard thing to change the lights. 10 minutes later I pulled forward to let the solitary car behind me trigger it, and with no oncoming traffic it changed almost instantly.I still don't know to this day if i was weight or magnetic field that changed it. Ambos and fire engines have light changers these days but i thought they worked like a remote control (most traffic lights have a small antenna on top if you look hard enough)
but the magnets may work in a similar way

[Badjelly]

I always thought it was a weight related thing...

Not since they got rid of the rubber-tube detectors. (How old do you have to be remember those? It's a long, long time since I've seen one.) You could usually trigger them with a well-directed stomp.

These days it's more of a volume-of-conductive-metal thing.

[Mystic13]

Not since they got rid of the rubber-tube detectors. (How old do you have to be remember those? It's a long, long time since I've seen one.) You could usually trigger them with a well-directed stomp.

These days it's more of a volume-of-conductive-metal thing.

lol.. rubber tube detectors... that sounds interesting.

Next thing you'll be trying to tell us about punch cards for computers or machines that swallow long lines of paper tape with holes in it.

I told my kids that microwave ovens didn't exist when i was a kid and they're shocked to hear that. "what? how did you heat things up?".

And here I am seeing the first new generation Samsung mobile phones with video projectors. I so want one of these. I have no idea what I'd use it for but...

http://www.gizmag.com/samsung-pico-p...e-phone/10773/

[Naki Rat]

lol.. rubber tube detectors... that sounds interesting.

Next thing you'll be trying to tell us about punch cards for computers or machines that swallow long lines of paper tape with holes in it.

I told my kids that microwave ovens didn't exist when i was a kid and they're shocked to hear that. "what? how did you heat things up?".

And here I am seeing the first new generation Samsung mobile phones with video projectors. I so want one of these. I have no idea what I'd use it for but...

http://www.gizmag.com/samsung-pico-p...e-phone/10773/

And rotary dial telephones, floor mounted headlight dipswitches and manual toll calls.

[Bass]

I don't know that these musings have any practical relevance, but I like to know this stuff. (Just like countersteering, really.) Time for some research...

Edit: Wikipaedia says they work like metal detectors:

Commercial metal detectors typically have an excitation coil and 2 detection coils. Metal coming into the field changes the phasing between the exciter and the detectors.
They also play around with the frequency used (and it's always way above 50 hz) according to what they are looking for. In this way, they can actually persuade the machine to ignore some stuff e.g. the metallised film used for packing potato chips and the like, so will can look only at the bag contents.
Obviously then, the magnetic properties of the metal to be detected, come into play, with magnetic materials e.g. mild steel, being the easiest to find, followed by ferrous-but-nonmagnetic e.g. austenitic stainless and then other alloys.
Lastly, shape and motion also play a part. A needle shaped object can be easily located in some orientations wrt the field but almost invisible in others.