Traffic Loop Sensor Trigger For Bikes

In article
,
" wrote:

On Nov 10, 4:44*pm, Michael Press wrote:
In article
,

" wrote:
On Nov 9, 11:11*am, Mike Rocket J Squirrel
wrote:
*From the "More Stuff on a Bicycle Is Better," Dept.

http://gizmodo.com/5079430/traffic-l...for-bikes-gets...

I wonder how this does on the sensors that are mounted to the light
and not embedded in the pavement? *On motorcycles, a common way to
trip the sensor if your bike doesn't have enough steel facing the
light is to angle the bike a bit and put your kickstand down. *I'm
guessing a bicycle kickstand still doesn't contain enough steel.

It need not be steel, only a conductive body that will have
eddy currents induced in it by the inductive loop in the pavement.

I take it that aluminum is far less conductive than steel then? I
know from experience of several of these sensors that my older mostly
steel Ninja would trip that the newer mostly aluminum R6 wouldn't.

Al is far more conductive than steel. Here are some selected values
for resistivity. Take the reciprocal to get conductivity.
I do not have the figures for Al alloys.

Ag 1.59
Cu 1.771
Au 2.44
Al 2.824
Fe 10
Steel 10.4
Pb 22

The differences encountered at traffic sensors is because
of the difference in the amount of mass present in a steel
a component from an Al component.

--
Michael Press

On Nov 10, 3:01*pm, " wrote:
On Nov 10, 4:44*pm, Michael Press wrote:
" wrote:

It need not be steel, only a conductive body that will have
eddy currents induced in it by the inductive loop in the pavement.

I take it that aluminum is far less conductive than steel then? *I
know from experience of several of these sensors that my older mostly
steel Ninja would trip that the newer mostly aluminum R6 wouldn't.

http://www.howstuffworks.com/question234.htm

Aluminum is a very good conductor. The issue here
is the inductance. Placing the metal object near the
wire loop changes the inductance of the loop. The
control circuit is monitoring the inductance by sending
an AC current through the loop and effectively measuring
the time constant. The metal bike acts like the
ferrous core that one puts inside a loop of wire to make
a useful inductor as an electrical component.
Aluminum also increases the inductance, but
not as effectively as iron because it has a much
lower magnetic permeability than iron.

http://en.wikipedia.org/wiki/Inductor
http://en.wikipedia.org/wiki/Magnetic_permeability

A traffic loop that does not detect an aluminum
motorcycle or aluminum bicycle wheels is
still misadjusted.

Ben

wrote in message
...
On Nov 10, 4:44 pm, Michael Press wrote:
In article
,

" wrote:
On Nov 9, 11:11 am, Mike Rocket J Squirrel
wrote:
From the "More Stuff on a Bicycle Is Better," Dept.

http://gizmodo.com/5079430/traffic-l...for-bikes-gets...

I wonder how this does on the sensors that are mounted to the light
and not embedded in the pavement? On motorcycles, a common way to
trip the sensor if your bike doesn't have enough steel facing the
light is to angle the bike a bit and put your kickstand down. I'm
guessing a bicycle kickstand still doesn't contain enough steel.

It need not be steel, only a conductive body that will have
eddy currents induced in it by the inductive loop in the pavement.

--
Michael Press

I take it that aluminum is far less conductive than steel then? I
know from experience of several of these sensors that my older mostly
steel Ninja would trip that the newer mostly aluminum R6 wouldn't.

DanKMTB,
Aluminum is much more conductive than steel:
http://tinyurl.com/684mkn
Some info on the operation of such sensors:
http://www.humantransport.org/bicycl.../detection.htm
Doesn't give any explanation of why the Ninja would work better than the
R6, though.
Kerry

wrote:
On Nov 10, 12:22 pm, peter wrote:
On Nov 10, 8:54 am, " wrote:

On Nov 9, 11:11 am, Mike Rocket J Squirrel
wrote:
From the "More Stuff on a Bicycle Is Better," Dept.
http://gizmodo.com/5079430/traffic-l...for-bikes-gets...
--
Mike "Rocket J Squirrel"
Bend, Oregon
I wonder how this does on the sensors that are mounted to the light
and not embedded in the pavement?
Some places have gone to optical/IR sensors instead of embedded
loops. These should detect motorcycles and bicycles.

On motorcycles, a common way to
trip the sensor if your bike doesn't have enough steel facing the
light is to angle the bike a bit and put your kickstand down. I'm
guessing a bicycle kickstand still doesn't contain enough steel.
No steel is required - the loop sensors are metal detectors which use
the same principle as the detectors people use at the beach to find
coins and jewelry. Anything that conducts electricity will trigger
the sensor. I frequently put my aluminum bike down to get the rims
and frame closer to the sensor and thereby trigger the light. This
works almost all the time - and I'm sure my Cannondale has much less
metal than your motorcycle.

BTW, the sensors are adjustable and can be set so they will detect
bicycles. If you have one that fails to do so then complain to the
local traffic engineering department and have them readjust the
sensitivity.



Hm.. also makes me wonder if there are actually sensors in the light,
or if the angle the bike part is pointless and all lowering the
kickstand does is get the steel closer to the pavement. Eh, either
way, when riding a mostly aluminum crotch rocket, the kick stand trick
works. I find when on a bicycle the "running the light" trick is good
enough. I can think of far more practical ways than this to add that
kind of weight to my bike. An espresso machine comes to mind right
out of the gate. So does a handlebar mounted harpoon gun. Perhaps a
tall skinny vanilla barista. Point being, there are better ways to
add a couple pounds to your bike. At least in my opinion.- Hide quoted text -
- Show quoted text -

Interesting. I was told to "point the kickstand at the light" by my
instructor when I learned that trick. That part is probably useless.
Dropping the stand does work though, I've sat through a couple cycles
and then dropped the stand and triggered the light in the past. Must
just be moving the stand closer to the sensor.

That sounds right. There's a balky sensor near my house. No bike
positioning will trigger it (I've sat through a few cycles more than
once to experiment). However, laying the bike (bicycle, not motorbike)
down does it every time. That's a bit awkward when, just as you lay it
down, a car finally arrives behind you - it's a left-turn lane. Too
lazy to call public works, now I go around the block instead.

Mark J.

On Nov 10, 7:56*pm, Mark wrote:
wrote:
On Nov 10, 12:22 pm, peter wrote:
On Nov 10, 8:54 am, " wrote:

On Nov 9, 11:11 am, Mike Rocket J Squirrel
wrote:
*From the "More Stuff on a Bicycle Is Better," Dept.
http://gizmodo.com/5079430/traffic-l...for-bikes-gets....
--
Mike "Rocket J Squirrel"
Bend, Oregon
I wonder how this does on the sensors that are mounted to the light
and not embedded in the pavement?
Some places have gone to optical/IR sensors instead of embedded
loops. *These should detect motorcycles and bicycles.

On motorcycles, a common way to
trip the sensor if your bike doesn't have enough steel facing the
light is to angle the bike a bit and put your kickstand down. *I'm
guessing a bicycle kickstand still doesn't contain enough steel.
No steel is required - the loop sensors are metal detectors which use
the same principle as the detectors people use at the beach to find
coins and jewelry. *Anything that conducts electricity will trigger
the sensor. *I frequently put my aluminum bike down to get the rims
and frame closer to the sensor and thereby trigger the light. *This
works almost all the time - and I'm sure my Cannondale has much less
metal than your motorcycle.

BTW, the sensors are adjustable and can be set so they will detect
bicycles. *If you have one that fails to do so then complain to the
local traffic engineering department and have them readjust the
sensitivity.

Hm.. *also makes me wonder if there are actually sensors in the light,
or if the angle the bike part is pointless and all lowering the
kickstand does is get the steel closer to the pavement. *Eh, either
way, when riding a mostly aluminum crotch rocket, the kick stand trick
works. *I find when on a bicycle the "running the light" trick is good
enough. *I can think of far more practical ways than this to add that
kind of weight to my bike. *An espresso machine comes to mind right
out of the gate. *So does a handlebar mounted harpoon gun. *Perhaps a
tall skinny vanilla barista. *Point being, there are better ways to
add a couple pounds to your bike. *At least in my opinion.- Hide quoted text -
- Show quoted text -

Interesting. *I was told to "point the kickstand at the light" by my
instructor when I learned that trick. *That part is probably useless.
Dropping the stand does work though, I've sat through a couple cycles
and then dropped the stand and triggered the light in the past. *Must
just be moving the stand closer to the sensor. *

That sounds right. *There's a balky sensor near my house. *No bike
positioning will trigger it (I've sat through a few cycles more than
once to experiment). *However, laying the bike (bicycle, not motorbike)
down does it every time. *That's a bit awkward when, just as you lay it
down, a car finally arrives behind you - it's a left-turn lane. *Too
lazy to call public works, now I go around the block instead.

Mark J.- Hide quoted text -

- Show quoted text -

Thanks to all of you for the explanations. Learn something new every
day. It seems the amount of mass is the only reasonable explanation
for the newer bikes not triggering sensors that older bikes, harleys
and other steel framed bikes trip without issue. Point: Mr. Press.

On Tue, 11 Nov 2008 16:52:11 -0800, Mike Rocket J Squirrel
wrote:

On 11/11/2008 1:56 PM Arthur Shapiro wrote:

Would the presence of a strong magnet affect these sensors? I don't
appreciate the behavioral distinction between magnetic flux and metallic mass
in the situation in question.

I'm not anxious to add extra riding weight, but these fancy new rare earth
magnets can pack a huge effect in a couple of ounces.

Art

Nope -- AC induction loop doesn't care about magnetic fields. All the loop
would "see" is the metal of the magnet, the field would be invisible.

Is there a single common frequency that all these things use? I've
toyed with the idea of building a light weight circuit with a small
antenna to disrupt the flux, but I don't care enough to build much
smarts into the system.

Pat

Email address works as is.

On 11/11/2008 6:34 PM Patrick Lamb wrote:

On Tue, 11 Nov 2008 16:52:11 -0800, Mike Rocket J Squirrel
wrote:

On 11/11/2008 1:56 PM Arthur Shapiro wrote:

Would the presence of a strong magnet affect these sensors? I don't
appreciate the behavioral distinction between magnetic flux and metallic mass
in the situation in question.

I'm not anxious to add extra riding weight, but these fancy new rare earth
magnets can pack a huge effect in a couple of ounces.

Art
Nope -- AC induction loop doesn't care about magnetic fields. All the loop
would "see" is the metal of the magnet, the field would be invisible.

Is there a single common frequency that all these things use? I've
toyed with the idea of building a light weight circuit with a small
antenna to disrupt the flux, but I don't care enough to build much
smarts into the system.

Dunno. If you're smart enough to build a circuit to counter the signal in
the loop, you're smart enough to hook a small loop to a battery-powered
oscilloscope and plunk it atop the sensor loop to see what it picks up.

--
Mike "Rocket J Squirrel"
Bend, Oregon

On Nov 11, 6:48*pm, Mike Rocket J Squirrel
wrote:
On 11/11/2008 6:34 PM Patrick Lamb wrote:





On Tue, 11 Nov 2008 16:52:11 -0800, Mike Rocket J Squirrel
wrote:

On 11/11/2008 1:56 PM Arthur Shapiro wrote:

Would the presence of a strong magnet affect these sensors? *I don't
appreciate the behavioral distinction between magnetic flux and metallic mass
in the situation in question.

I'm not anxious to add extra riding weight, but these fancy new rare earth
magnets can pack a huge effect in a couple of ounces.

Art
Nope -- AC induction loop doesn't care about magnetic fields. All the loop
would "see" is the metal of the magnet, the field would be invisible.

Is there a single common frequency that all these things use? *I've
toyed with the idea of building a light weight circuit with a small
antenna to disrupt the flux, but I don't care enough to build much
smarts into the system.

Dunno. If you're smart enough to build a circuit to counter the signal in
the loop, you're smart enough to hook a small loop to a battery-powered
oscilloscope and plunk it atop the sensor loop to see what it picks up.

I have a friend who says that if the light does not turn green, you
can treat it as broken and proceed through the intersection when
safe. I have not been able to find any support for this statement in
the UVC. -- Jay Beattie.

On Nov 11, 6:34*pm, Patrick Lamb wrote:
On Tue, 11 Nov 2008 16:52:11 -0800, Mike Rocket J Squirrel

wrote:
On 11/11/2008 1:56 PM Arthur Shapiro wrote:

Would the presence of a strong magnet affect these sensors? *I don't
appreciate the behavioral distinction between magnetic flux and metallic mass
in the situation in question.

I'm not anxious to add extra riding weight, but these fancy new rare earth
magnets can pack a huge effect in a couple of ounces.

Art

Nope -- AC induction loop doesn't care about magnetic fields. All the loop
would "see" is the metal of the magnet, the field would be invisible.

Is there a single common frequency that all these things use?

Don't think so. They're generally in the 20 - 40 kHz region but AFAIK
it's not standardized.
BTW, the advantage of iron for E-M induction is primarily at very low
frequencies. At typical loop detector frequencies non-magnetic metals
work just as well. So aluminum bikes and rims are equally effective
as steel ones. The problem is just insufficient quantity unless the
detector sensitivity is turned up.

On Tue, 11 Nov 2008 20:34:09 -0600, Patrick Lamb wrote:

On Tue, 11 Nov 2008 16:52:11 -0800, Mike Rocket J Squirrel
wrote:

On 11/11/2008 1:56 PM Arthur Shapiro wrote:

Would the presence of a strong magnet affect these sensors? I don't
appreciate the behavioral distinction between magnetic flux and
metallic mass in the situation in question.

I'm not anxious to add extra riding weight, but these fancy new rare
earth magnets can pack a huge effect in a couple of ounces.

Art

Nope -- AC induction loop doesn't care about magnetic fields. All the
loop would "see" is the metal of the magnet, the field would be
invisible.

Is there a single common frequency that all these things use? I've
toyed with the idea of building a light weight circuit with a small
antenna to disrupt the flux, but I don't care enough to build much
smarts into the system.

Pat

Email address works as is.


when is someone going to post details for the priority trigger signal
transmitters that emergency vehicles use? because then the whiners can
enjoy holding up their hands in horror at the morality of abuse.