I saw that there is a new type of proximity sensor for parking assistance.

I forgot almost everything of basic physics, and I am curious to know if somebody can explain how this kind of circuit runs.
http://www.carparkingsensordirect.com
Basically, the website says that there is an antenna on the back of the van, a adhesive antenna made of aluminium. The magnetic field varies when a wall or an object enters in the space occupied by the magnetic field.

But I we can measure the magnetic field?
Any help appreciated
G

You can measure the magnetic field by using a Hall effect proximity sensor.

To ssylee.

Yes I know that. But they do all with the same "antenna". Did you take a look at the website I attached?
Thanks

Thank you very much,
I did not know at all about it.
I will try to build some prototype and I will tell you my results!
G

I built a simple one about a year ago with a sensor that was about 7 cm long and had a detection range for my hand of 12 to 14 inches. The key to making it work, which is even mentioned in the advertisement, is to standardize or calibrate whenever you first turn it on. Good luck. John

However, if we put an inductance as sensor the effect should be the same.
Also coils change their inductance if an object is near.
A long string of aluminium could be a good inductor?
G

No, I mistaken. The inductance changes if a metal object is close!
G

A frequent contributor to this forum, Chemelec, has designed a nice, inductance-based detector for cars. See:

http://www3.telus.net/chemelec/Proje...p-Detector.htm

However, from my understanding of what you want to do, I don't think that is the answer. For detecting any object at distances of 15 cm or more, I think your best chance is with capacitance, ultrasound, or reflected IR/light.
John

I think to realize the sensor by using a capacitive sensor and a Wien Oscillator.
Anyone of you have some suggestions for buildings a capacflector?
G

I see, thank you.
But I mean if you have some suggestion on how to build practically the sensors, not the circuitry.G

The NASA publications include a student report that has a step by step procedure, including dimensions and PCB layouts, for building an obstacle avoiding robot. For the sensor I built, I just used PCB material for the conductive surfaces and clear packing tape for the dielectric layers.

I can't be much more definite than that. The student report I referenced was done at Michigan State University (http://www.egr.msu.edu/classes/ece480/goodman/), but that site has been updated to 2007. The report you want is from November, 2004. I believe that report is still available on the NASA links. You might try to contact Prof. Goodman (the faculty advisor at MSU) directly; however, I would suggest that first you get on the internet and search the references already provided. Second, you need define better exactly what you want to do. John

Ok, I'll take a look.
However, my original goal is to build a simple proximity sensor for my car.
I think to use the relaxation oscillator with its capacitor coupled with the sensor.
The sensor should be put in the baggage van of the car and should be small.
I think to make a long strip of aluminium and use paper as dieletric.
G

Originally Posted by jpanhalt

The NASA publications include a student report that has a step by step procedure, including dimensions and PCB layouts, for building an obstacle avoiding robot. For the sensor I built, I just used PCB material for the conductive surfaces and clear packing tape for the dielectric layers.

I tried to connect to urls but they seem broken.
May you attach a pic of your sensor?
G