"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

TIA
Jim K

"Jim K" wrote in message ...
"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

TIA
Jim K

What do you want to know about them, how they work?
In their most basic form they form the "L" of an L-C oscillator which changes
frequency when a tonne or so of ferrous metal drives over it.

Usually called sub-surface coils.

http://www.roadtraffic-technology.co...traffic-tech2/

I suppose it's only a matter of time before the vehicle VIN will be read by RFID
as OCR (ANPR) can't be 100% reliable.

--
Graham.

%Profound_observation%

On Mar 16, 11:38 am, Owain wrote:
On Mar 16, 10:45 am, Jim K wrote:

"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

a search for vehicle loop produced

http://groups.google.com/group/uk.d-...hread/dadc7b3f...

OT: Traffic monitoring cables across road - June 2007

and

http://groups.google.com/group/uk.d-...hread/d7521361...

Power operated gates - Oct 2009

Owain

I thank you Sir, but alas neither is what I recall :(.

I asked a few detailed questions of a discussion and got some good
pointers out
(the "Jim" in the above links is not me ;))

On Mar 16, 11:30 am, "Graham." wrote:
"Jim K" wrote in ...
"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

TIA
Jim K

What do you want to know about them, how they work?

how to and costs of installing one...

seen the detector unit parts on ebay, and read about the loops -
(just want to refresh on what I found out last time before I bother
anyone again ;))

Jim K

Jim K wrote:
"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

Search for Golden River. Make sure safesearch is on if doing this from
work.

"Jim K" wrote in message
...
On Mar 16, 11:30 am, "Graham." wrote:
"Jim K" wrote in

m...
"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

TIA
Jim K

What do you want to know about them, how they work?

how to and costs of installing one...

seen the detector unit parts on ebay, and read about the loops -
(just want to refresh on what I found out last time before I bother
anyone again ;))

Jim K

My understanding is that the loops are installed with a machine resembling a
giant angle grinder, so this is a very on-topic question.
For example: http://www.motivation-tc.co.uk/loop1.htm

I used to write software for computer systems that collected data from
traffic loop sites, but I was never involved with the loops themselves or
the kit in the roadside cabinets. My impression is that these loops and
their control circuitry operate on the principle of a tuned LC-circuit being
detuned by a passing lump of iron. At first glance, it sounds like something
that might be DIYable after a visit to Maplin. If you are going to cut the
slots yourself, be careful that there are no services buried in the
roadway - this is common problem for commercial loop-installers.

On Mar 16, 7:34 pm, "BluntChisel" wrote:
"Jim K" wrote in message

... On Mar 16, 11:30 am, "Graham." wrote:
"Jim K" wrote in


m...



"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?

TIA
Jim K

What do you want to know about them, how they work?

how to and costs of installing one...

seen the detector unit parts on ebay, and read about the loops -
(just want to refresh on what I found out last time before I bother
anyone again ;))

Jim K

My understanding is that the loops are installed with a machine resembling a
giant angle grinder, so this is a very on-topic question.
For example:http://www.motivation-tc.co.uk/loop1.htm

I used to write software for computer systems that collected data from
traffic loop sites, but I was never involved with the loops themselves or
the kit in the roadside cabinets. My impression is that these loops and
their control circuitry operate on the principle of a tuned LC-circuit being
detuned by a passing lump of iron. At first glance, it sounds like something
that might be DIYable after a visit to Maplin. If you are going to cut the
slots yourself, be careful that there are no services buried in the
roadway - this is common problem for commercial loop-installers.

thanks for notes-
It will be OK (I hope) on the dirt track and I plan to embed loop into
slab as poured.

Cheers
Jim K

Jim K wrote:
On Mar 16, 7:34 pm, "BluntChisel" wrote:
"Jim K" wrote in message

... On Mar 16, 11:30 am, "Graham." wrote:
"Jim K" wrote in

m...



"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?
TIA
Jim K
What do you want to know about them, how they work?
how to and costs of installing one...
seen the detector unit parts on ebay, and read about the loops -
(just want to refresh on what I found out last time before I bother
anyone again ;))
Jim K
My understanding is that the loops are installed with a machine resembling a
giant angle grinder, so this is a very on-topic question.
For example:http://www.motivation-tc.co.uk/loop1.htm

I used to write software for computer systems that collected data from
traffic loop sites, but I was never involved with the loops themselves or
the kit in the roadside cabinets. My impression is that these loops and
their control circuitry operate on the principle of a tuned LC-circuit being
detuned by a passing lump of iron. At first glance, it sounds like something
that might be DIYable after a visit to Maplin. If you are going to cut the
slots yourself, be careful that there are no services buried in the
roadway - this is common problem for commercial loop-installers.

thanks for notes-
It will be OK (I hope) on the dirt track and I plan to embed loop into
slab as poured.

You should be able to modify a standard metal detector circuit to work.
--
Tciao for Now!

John.

On Mar 16, 7:47 pm, John Williamson
wrote:
Jim K wrote:
On Mar 16, 7:34 pm, "BluntChisel" wrote:
"Jim K" wrote in message

.... On Mar 16, 11:30 am, "Graham." wrote:
"Jim K" wrote in

m...

"yonks" ago I asked for and kindly received info about buried
inductive loops used to detect vehicles on a roadway - I can't find it
now (thanks Google) - Can anyone with superior newsgroup searching
capability find it and post a link?
TIA
Jim K
What do you want to know about them, how they work?
how to and costs of installing one...
seen the detector unit parts on ebay, and read about the loops -
(just want to refresh on what I found out last time before I bother
anyone again ;))
Jim K
My understanding is that the loops are installed with a machine resembling a
giant angle grinder, so this is a very on-topic question.
For example:http://www.motivation-tc.co.uk/loop1.htm

I used to write software for computer systems that collected data from
traffic loop sites, but I was never involved with the loops themselves or
the kit in the roadside cabinets. My impression is that these loops and
their control circuitry operate on the principle of a tuned LC-circuit being
detuned by a passing lump of iron. At first glance, it sounds like something
that might be DIYable after a visit to Maplin. If you are going to cut the
slots yourself, be careful that there are no services buried in the
roadway - this is common problem for commercial loop-installers.

thanks for notes-
It will be OK (I hope) on the dirt track and I plan to embed loop into
slab as poured.

You should be able to modify a standard metal detector circuit to work.
--
Tciao for Now!

John.

intellisting ! anyone care to hold me hand !? NB Ebay has purpose
designed detector board/units for £30 odd...

Jim K

In article
, Jim
K writes
On Mar 16, 7:47 pm, John Williamson
wrote:
Jim K wrote:

thanks for notes-
It will be OK (I hope) on the dirt track and I plan to embed loop into
slab as poured.

You should be able to modify a standard metal detector circuit to work.

intellisting ! anyone care to hold me hand !? NB Ebay has purpose
designed detector board/units for £30 odd...

A piezo cable sensing solution may offer a simpler (cheaper) solution.

Google for piezo cable traffic sensor for plenty of hits inc this apps
note from Rapid Electronics:

http://www.rapidonline.com/netalogue...ZO%20CABLE.pdf
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

fred wrote:
In article
, Jim
K writes
On Mar 16, 7:47 pm, John Williamson
wrote:
Jim K wrote:

thanks for notes-
It will be OK (I hope) on the dirt track and I plan to embed loop into
slab as poured.

You should be able to modify a standard metal detector circuit to work.

intellisting ! anyone care to hold me hand !? NB Ebay has purpose
designed detector board/units for £30 odd...

A piezo cable sensing solution may offer a simpler (cheaper) solution.

Google for piezo cable traffic sensor for plenty of hits inc this apps
note from Rapid Electronics:

http://www.rapidonline.com/netalogue...ZO%20CABLE.pdf

Piezo cable needs to be close to the surface on a fairly rigid base, so
embedded into a concrete slab or tarmac with its top almost at surface
level, covered by a sliver of mastic or similar to secure it, waterproof
it, and keep the worst of the impact away. It's good enough and
consistent enough to use as a built in weighbridge on a motorway with
the right electronics. At least, VOSA think it is.

For the metal detector, you have two oscillators running at the same
frequency, and a beat detector. The advantage is that the sensing coil
doesn't need to be held rigidly, whereas the piezo cable has, if only to
protect it from permanent distortion by traffic. The loop, which can be
mains flex or similar, can be buried under a couple of inches of earth
and still work. I'd not guarantee the piezo would stand for that.

Circuit here as a start:-

http://www.electronic-circuits-diagr...sorsckt4.shtml

And click on the link for the diagram. The sensing coil is shown as L1,
with 20 turns of wire on a 4 inch core, but if you lay it out as a
rectangle on the ground, you'd just add or subtract turns to get the
same impedance. We've got a similar arrangement under the tarmac near
our depot gate that will detect a bushbike, but not steel toecapped boots.

The ready built boards will be a variation on that circuit, probably.

Also, if you need to remove the expensive bit for safe keeping, a plug
and socket connector will let you do that and use the unit in more than
one place if you match the buried coils fairly closely. That also
applies to the piezo, but without the need to recalibrate when you move
it, but with the proviso that the connection has to present an extremely
high resistance and low capacitance between the wires.

To get a pulse per vehicle, you need a detector on the audio output,
feeding a schmitt trigger, then interface to the rest of the logic.



--
Tciao for Now!

John.

In article ,
John Williamson wrote:
... vehicle loop detectors ...
}You should be able to modify a standard metal detector circuit to work.

That's more complicated than necessary as vehicles are much bigger than
the items metal detectors are typically designed to detect.

All you need is an oscillator circuit which runs at about 50kHz to
100kHz when connected to your loop (which is typically three turns of
wire). You detect the vehicle by the change in the oscillator
frequency when there is something over the loop because it changes the
inductance of the loop.