Finding a loop detector

Frank Krygowski writes:

On Monday, October 14, 2013 9:59:41 PM UTC-4, Jeff Liebermann wrote:
If you want, I can throw something together (time
permitting) and see what it produces.

Well sure, if you like. But I'm hoping for something as simple as possible.


Maybe that's why the EE Masters candidate chose another project.

snip

On Mon, 14 Oct 2013 18:59:41 -0700
Jeff Liebermann wrote:

If you have a smartphone of some flavor, you can probably use one of
the oscilloscope apps to act as the amplifier, detector, and display.

https://play.google.com/store/apps/details?id=com.codebros.emffree&hl=en

This one certainly detects how close the phone is to a running computer.
Heh, it's a start. Sadly the nearest traffic light is a 25 minute cycle
ride away, and it's raining....

I'll be giving it a try next time I'm at a light. Thanks for the
suggestion Jeff.



Mike

On 10/14/2013 8:29 PM, datakoll wrote:
1850


Yes, #1850 is the strobe bulb for a Belt Beacon:

http://www.elightbulbs.com/catpics/eiko/40394alg.jpg

(I'm good with Simplex part numbers too)

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Monday, October 14, 2013 10:45:59 PM UTC-4, Frank Krygowski wrote:
On Monday, October 14, 2013 9:59:41 PM UTC-4, Jeff Liebermann wrote:

If you want, I can throw something together (time

permitting) and see what it produces.



Well sure, if you like. But I'm hoping for something as simple as possible.



I've posted the question on a couple other lists. Before putting any time into it, you might want to wait to see if there's a known solution out there. Thanks for the offer, though.

OK, someone elsewhere pointed out that there are commercial devices available.
http://www.atsi-tester.com/index.php...rs/loop-finder

Only $400! :-(

- Frank Krygowski

On Monday, October 14, 2013 10:43:37 PM UTC-4, Jay Beattie wrote:

BTW, I have a friend who is convinced that you can treat a non-responsive turn signal as "broken" and may permissibly run the light. After ferreting through our version of the UVC, I found nothing to support that belief -- meaning that you can't run the light if you don't trigger the loop. I'm not clear on what you are supposed to do, however. I run the light -- but I look for cops first.

The worst situation may be a left turn lane on a busy road, where the LT light stays red until a vehicle is detected. It seems pretty irrational to sit there forever when you're not detected, so it seems it should be easy to fight a ticket for safely disobeying an unresponsive red.

Here in Ohio, we're trying to get that specifically written into law. Our bill is depressingly stuck in committee.

- Frank Krygowski

Lieb,

excuse.....idea is finding the sweet spot for bicycle/weight activation ?

where's the signal ?

On Mon, 14 Oct 2013 19:09:03 -0700 (PDT), Jay Beattie
wrote:


So, is there a cell phone app for triggering the loop?
-- Jay Beattie.

Yes. Tie a string onto your cellphone and suspend it over the loop.
The metal in the cell phone should trigger the vehicle detector.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 15 Oct 2013 13:30:26 +1100, James
wrote:

You will have fun listening to 200kHz signals with a microphone input
circuit and A/D. Often the maximum sample rate is 192kHz for high end
audio A/D converters. I don't know what phone circuits are capable of,
but I'd be surprised if it was that high.

200KHz won't work on an Android. I think (not sure) that the sampling
rate is 44KHz giving a maximum frequency response of about 22 KHz.
https://play.google.com/store/apps/details?id=com.DanielBach.FrequenSee&hl=en
https://play.google.com/store/apps/details?id=com.electronchaos.SpeedySpectrumAnalyze r&hl=en
20 Hz to 22 KHz. I'll dig deeper when I have time.

Unfortunately, the vehicle detector I tried used about 80 Khz, so
that's not going to work. A mixer, local oscillator, down converter,
and anti-aliasing filter will work, but I wanted to avoid building
anything complexicate.

Somehow, I don't want to mount a DSO (digital storage oscillosope) on
my bicycle.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 15 Oct 2013 10:15:41 +0100, Mike Causer
wrote:

On Mon, 14 Oct 2013 18:59:41 -0700
Jeff Liebermann wrote:

If you have a smartphone of some flavor, you can probably use one of
the oscilloscope apps to act as the amplifier, detector, and display.

https://play.google.com/store/apps/details?id=com.codebros.emffree&hl=en

Oh swell. AVG virus scan on my Droid-X2 declared the above program to
be spyware. Might be a false alarm and I don't have time to
investigate. There are other apps.
https://play.google.com/store/search?q=emf%20meter&c=apps&hl=en

This one certainly detects how close the phone is to a running computer.
Heh, it's a start. Sadly the nearest traffic light is a 25 minute cycle
ride away, and it's raining....

I'll be giving it a try next time I'm at a light. Thanks for the
suggestion Jeff.

You might try one of the audio spectrum analyzer applications instead
of the oscilloscope. That will (hopefully) show what frequency is
being used.

Of course, the pickup loop would be better if the frequency is
unknown. I guess an untuned big loop might be a good start. Input
impedance of the smartphone is rather high, so there's no need for a
transformer.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Mon, 14 Oct 2013 19:45:59 -0700 (PDT), Frank Krygowski
wrote:

On Monday, October 14, 2013 9:59:41 PM UTC-4, Jeff Liebermann wrote:
If you want, I can throw something together (time
permitting) and see what it produces.

Well sure, if you like. But I'm hoping for something as simple as possible.

I'll need to know the frequency of operation. I can calculate the
field strength. That will produce a pickup loop design. From that, I
can design a "simple" circuit for the purpose. PCB if you want (time
permitting). I'm thinking of an LED lighting up when it gets a signal
in the desired frequency range, something like a dielectric stud
finder or nail detector.

I've posted the question on a couple other lists. Before putting any time
into it, you might want to wait to see if there's a known solution out there.
Thanks for the offer, though.

Ok. Procrastination comes easily for me.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558