Choose a proper magnetic field sensor

[matriX_1500]

Hi, i'm designing a smart parking and want to use magnetic field sensor on the ground (under the car) to detect the parking free/busy status.
I prefer magnetic field sensor because ultrasonic need straight line of sight and cannot work within the box. And infrared sensor have problem in sun light. Other sensors cannot work on the 20-100 Cm distance (If this consideration have fault, please tell me)
So i need help to choose a proper "chip" for my PCB that have a cheap price.
Thanks

[FvM]

How do you detect car presence with a magnetic field sensor?

I would suggest a sensor loop as used for traffic light control.

[kripacharya]

Try using SPAD LiDaR device, like VL53L0X for your purpose. Depending on what you are envisioning this might work better. Be aware that this too gets limited in bright outdoor direct sunlight.

[eziggurat]

You could try the TI mm wave sensors.

[KlausST]

Hi,

In my eyes the simplest, with low effort should be an ultrasonic sensor.
But it's not clear to me why you think it will not work in your case.
--> please make a draft about your application.

There are already car detectors in parking houses... how do they work? Can't you use them as proven technique?

Klaus

[matriX_1500]

Ultra Sonic cannot work behind a plastic box. So, i need a sensor that be able to detect material: detect metal of car's body and not deceiving with my plastic box.
and about direct sunlight problem => that is crucial. because my application is on-street

[KlausST]

Hi,

You don't give much information. You will have your reasons, but it makes it almost impossible to help.

Regarding IR and sunlight: usually sunlight is cancelled out by modulating the IR source and detecting the modulation signal...

Klaus

[BradtheRad]

I was just about to recommend something like an electronic compass made from hall sensors (example, digital compass in automobiles). But hall sensors respond to a magnetic field, and steel cars lack magnetism to influence a hall sensor.

What kind of compass is in my steel car? By an internet search it appears that a different strategy is used in such compasses. A large ferrous mass alters the response of a hall sensor (or parallel hall sensors, or anti-parallel hall sensors) to the earth's magnetic field. This needs to be subtracted, but for your project it may work as a vehicle detector.

The article below might have a method you can use to detect a steel vehicle.

http://www.safety-devices.com/how-do...work-a-12.html

[c_mitra]

How about a large area coil using the principles of metal detector? They can have rather longer range and not affected by light etc etc.

[c_mitra]

because ultrasonic need straight line of sight and cannot work within the box. And infrared sensor have problem in sun light.

The transducer can be mounted outside the box; it is quite robust. IR sensors are modulated; just like a remote control they can work in outdoor light. Will the magnetic field sensor will work at 100cm?

Others have already pointed out some of these...