Metal detector circuit, low power
Metal detector circuit, low power
(OP)
Does anyone know of a low power metal detection device. We'd like to put this in a parking space mounted in a metal box on the ground, and when a car moves into the space, sense that a car is present. It has to be located outside in the rain and snow, sleet and oil (from cars leaking).
It's a battery powered detection mechanism, so low power is key.
One thought is RF transmit and receive, short burst every minute.
Any options or hints are appreciated.
Thanks,
kch
It's a battery powered detection mechanism, so low power is key.
One thought is RF transmit and receive, short burst every minute.
Any options or hints are appreciated.
Thanks,
kch





RE: Metal detector circuit, low power
But more recently, the traffic folks have started to use cameras and vision systems to detect cars.
Another option might the old break the IR beam trick.
RE: Metal detector circuit, low power
VE1BLL is right the latest is to use cameras. You will see them mounted on top of the signal light arms. They are crummy cameras who's only point is to note something the size of a motorcycle being there or not. Actually they notice a sudden change of view only.
You could actually do the same or you could use a high quality camera to actually see a large area and then use software. You snap a view empty then the SW compares the empty shot, parking spot, by parking spot, to see if there is a difference.
What kind of parking lot and why are you monitoring it? This can vary the methods too.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Metal detector circuit, low power
http://www.eistraffic.com/rtms_features.html looks promising. Got that from http://www
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Metal detector circuit, low power
The response time can be a few seconds up to 10 seconds possibly.
I was hoping for a low power chip measuring inductance or Capacitive, i.e. low frequency sensor that uses little power. Maybe just an RL or RC circuit with oscillator and detector at low enough frequency that a car atop the inductor can change the value enough to show a large metal presence. Silly? ?????
Sounds like maybe RF at 433
Mhz, with tx and rx antennas that are somewhat isolated is the way we are proceding. Possibly the 2.4 Ghz band, which we are already using.
any more thoughts?
kch
RE: Metal detector circuit, low power
See pg6 of the pdf.
http://www.nve.com/Downloads/expo00.pdf
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RE: Metal detector circuit, low power
I expect that traditional traffic-sensing loops (maybe 6 x 12 feet) would be in the xx kilohertz range (this is a guess).
If you wanted to use high frequencies, then you'd be looking at more of a radar (refelction) approach. And then IR reflections become easier. Think bathroom hands-free faucets, towel dispensers and hot air hand dryers. Not to mention auto-flushing urinals. Range of up to several feet should be easy.
RE: Metal detector circuit, low power
Dirt cheap, wireless, battery supplied and they'd pick up the heat from the car enigine.
Benta.
RE: Metal detector circuit, low power
Any cheap microcontroller can measure echo delay times, waiting for a big difference lasting long enough, to assume there's a parked vehicle in front of it.