Red light trigger test - starting up

[lewellen]

Hi, folks,

Well, I'm now officially sick of the under-sensitive traffic light sensors around Monterey. More than half of them don't seem to recognize my bike at first, and most of those (especially the left-turn lanes) don't trigger when using tricks like "wagging" the centerstand up and down.

So, I bought a couple of 3" long x 1/4" diameter Nd magnets from K&L Magnetics. My intent is to put them on either side of the centerstand down legs, near the base. That way I can swing them down towards the road also. I'm still thinking about how to mount them, but probably I'll slip the magnets inside some plastic tubing (for weather and road debris impact protection - Nd magnets are often brittle) and tie-wrap the packages to the centerstand.

If this works, the total cost of the fix should be somewhere under $25.

Good roads (and hopefully green lights),

- John L.

[celticus]

Let us know how it works.

Mark

[NeilS]

Well, I'm an electrical engineer, and I can't figure out how a magnet can trigger those vehicle detector loops. They sense the amount of iron within the loop, not magnetism, not motion, not non-ferrous metals. If anyone can explain it otherwise at a technical level, not just with war stories, please feel free to set me straight. But I don't think a magnet will be any bit more effective than the same amount of plain steel.

Around here, BTW, the state highway department is very interested in learning about lights that don't change in response to motorcycles. When they installed a new signal in my town and it didn't pick up my bike, it took less than three days after my call to have the sensor adjusted properly.

[indigoid]

Waste of money for what I hear is a snake-oil product. If a red light won't go green for you:

(1) put your bike in neutral

(2) flip the sidestand down such that the foot rests on one of the loops (lean the bike over onto it)

(3) flip sidestand back up

(4) engage first gear

Works for me every time... have tested on plenty of "difficult" lights around here, and have heard similar things from quite a few people in North America

[ka5ysy]

Here ya go: This is an article that explains the operation of the system:

http://www.humantransport.org/bicycledr ... ection.htm

[Dan-A]

I usually wait for one cycle, if it ignores me, I run it. If it is too busy, I go around.

Some signals are now employing a camera, and I understand they sense changes in the pixels so it is not dependent on how much iron you are packing.

[NeilS]

Good article, ka5ysy. I'll withdraw my comment about non-ferrous metals. Magnets still don't make any sense.

[lewellen]

Good article, ka5ysy. I'll withdraw my comment about non-ferrous metals. Magnets still don't make any sense.

Well, actually, they could, depending on the details of the system.

Moving a magnet over a loop of wire generates a transient voltage; this is basically how generators work.

If the detection system is configured to do so, such a transient could also be flagged as a means of determining a vehicle is present.

At any rate, the lights around here that are proving problematic do not respond to things like swinging the centerstand or side stand down. So, since I'm not willing to attach a large flat plate of sheet metal horizontally under my bike ... this is about the only option I have left, other than to keep waiting and then going through red lights.

Good roads,

- Lewellen

[indigoid]

merely flapping your sidestand in the breeze isn't going to help. You need to rest the foot on the induction loop. It works. Try it. Remember to check your mirrors and select neutral first to avoid killing the engine.

[NeilS]

Well, actually, they could, depending on the details of the system.

Moving a magnet over a loop of wire generates a transient voltage; this is basically how generators work.

If the detection system is configured to do so, such a transient could also be flagged as a means of determining a vehicle is present.

Of course, they could. But they don't. They don't because there's no reason for them to. The designers don't EXPECT that the target vehicles will have magnets attached to their bottoms.

There are many systems that COULD be designed to reliably detect the presence of a vehicle. But we have to deal with the technology that's already deployed.

[lewellen]

merely flapping your sidestand in the breeze isn't going to help. You need to rest the foot on the induction loop. It works. Try it. Remember to check your mirrors and select neutral first to avoid killing the engine.

... which is why I make it a point to ride up to a light as close to the edge of the loop as I can in the first place.

I have tried it, and no, in point of fact it doesn't work on several of the lights in my area that are on my daily commute - especially the left-turn lanes. This is why I'm trying this experiment.

Re the sidestand, if you have a centerstand, swinging it down on the sensor loop is about as easy as the sidestand, and doesn't risk cutting out the engine if you've left it in gear - that's why I generally prefer to use it for this trick. In either case, the amount of metal moving closer to the loop is about the same.

Second the comment re mirror checks - it's a good thing to be doing any time you're coming to a stop.

Of course, they could. But they don't. They don't because there's no reason for them to. The designers don't EXPECT that the target vehicles will have magnets attached to their bottoms.

*sigh* Engineers.

Yes, I know the designers are most likely not expecting to have vehicles with magnets strapped to their bottoms. The whole point, however, is that the system is not responding as it should to the "proper" signal it does receive from my motorcycle.

If you Fourier transform a voltage spike (which you get from the dB/dt term as the magnet moves over the wire loop), you get a range of frequencies. If these have enough amplitude in the band over which the detector system is operating, and if the detector is sensitive to a frequency response transient in that band, then you stand a chance of triggering the detector.

Among other things, the frequency spread of the transient will depend on the speed of the transit of the magnet over the loop, and the amplitude will depend on the strength of the magnetic field. It does me no good if I need to be going 90 mph over the loop to get it to trigger, nor if I need a 3T field at the road surface to get the required amplitude.

*shrug* As I said, it will depend on the details of the detector system's calibration, filtering and response to transients - not what it was designed to "look" for but rather how it responds to other signals. This is why this is an experiment, not a guaranteed fix.

At any rate, since the side- and center-stand tricks don't work on the particular lights I'm having trouble with, and I'm not about to mount a large chunk of metal under my bike, I'm open to any other suggestions you might have. (I'd rather not mount a wire loop and frequency sweep generator to my bike, albeit it might work- the EW guys might have something ... Hmmm....)

Good roads,

- Lewellen

[ShinySideUp]

Well I'm no engineer, and being gullible by nature, I bought some of them magnet thangs and wire-tied 'em onto my frame, right there by the centerstand, and by golly, the recalcitrant stoplight at the entrance to the complex where I live, the source of my daily cursing, now changes for me almost all the time.

Your Signal May Vary. Especially if you divide the force field delta by pi.

[webmost]

I did this years ago with a big red magnet from the local Ace hardware on my Honda CX500. Worked great. Before the magnet, could never ever get a green out to the main road from home; almost never to the main road from the office park. After the magnet, I always tripped the signal, at both places.

BTW -- tried one of those green light triggers sold as a motorcycle accessory. The magnet was too eenie weenie weak to make a diff.

It works.

[NeilS]

I'm open to any other suggestions you might have.

Why not try the political solution before the technical approach? If it's only a small number of lights in your neighborhood, find out who's responsible for them and ask that the controllers be readjusted. That way you'll be helping all the motorcyclists (and maybe bicyclists) in your area.

Start with the local police. They're usually the ones who call in burned-out light bulbs, so they should know who "owns" the light.

In the case of my favorite local signal, I spoke to the signals engineer at my town's district at the state highway department. He told me that the controllers are often adjusted to the minimum sensitivity that will detect the highway crew's pickup truck. That's not policy, it's what the (lazy) crews tend to do. He wants to know about signals that are not working properly (and detecting a motorcycle IS part of "working properly"), and he had the light fixed in just a few days.