can Inductive Sensor (PCB Coil of larger dimension) can sense up to 20cm

Hello Abhishek,

LDC can definitely be used to sense a distance of up to 20 cm using an appropriate size PCB coil.

LDC1000, LDC131x can sense targets

• up to 50% of the coil diameter (high-precision applications) and
• up to 100% of the coil diameter (low-precision applications such as metal presence detection)

LDC161x can sense targets up to 200% of the coil diameter.

The key here is the inductive sensor size.

I am sorry that WEBENCH currently provides a maximum target distance of 7 cm. We are working on updating it.

Please let me know if you need any additional information.

-Best Regards,

 Suhas R C

 

Hello Suhas,
Thanks for reply but as WEBENCH directly gives files of PCB design in Altium upto 7 cm and makes sure the LC circuit will sense the metal within 7cm. But in my case If I design the coil of larger trace and larger turns what will be the steps to make sure the LDC is sensing till 20 cm? Where I can simulate my PCB coil?

regards,
Abhishek Kadam

Abhishek,

You can use "Inductive Sensing Design Calculator Tool" in the below link to calculate sensor frequency, inducatance of coil using other dependent parameters such as trace width, space, turns etc.

http://www.ti.com/product/LDC1101/toolssoftware

Can you provide more information about your application such as whether you just want to detect presence or what is the resolution requirement in your application? If you can provide me the required information such as sensor frequency, target distance, resolution, I can help you design the coil.

I can also share the altium scripts to generate sensor coils.

-Best Regards,

 Suhas R C  

Hello Suhas,
Once again thanks for reply. I am designing system to detect vehicle in parking system. Earlier I designed the induction loop but due to some installation constraint I have to drop the plan.

With Inductive sensor I am thinking that If I install them in parking slot facing towards the car(induction loop is generally buried in ground, they are 6 feet in dimension, hence some what inconvenient) and If they can sense the metal by the range of 20-30 cm, I am good.

I will appreciate any feedback from your side.

Regards,
Abhishek Kadam

Abhishek,

Presence detection does not require high resolution.

Can you please clarify what is 6 feet in dimension?

Inductive sensor (buried in ground) can be used to detect a target at a distance of 20-30 cm provided the thickness of any other material (metal) in between is small enough that it does not interfere with the sensing.

-Best Regards,

 Suhas R C

Hello Suhas,
Yes I agree presence detection does not require high resolution.
The conventional induction loop is 6 feet in diameter which is very inconvenient to install and implement.
Below is the links for how ideal loop works.

humantransport.org/ncbikeed

www.fhwa.dot.gov/.../chapt5b.cfm

Inductive loop is buried in ground and it can sense the car(front axle or engine) .

In my application I am not installing it inside ground.What I can do is at the end of parking slot I am thinking to install some stands which will hold the LDC PCB , When it will detect the metal(back side of car/or rear wheel I can send this signal to controller.

Induction loop(ground one) can sense up to 1 meter but I am thinking if I am able to sense 20-30 cm(LDC inductive sensing) for my application I am good.

Regards,
Abhishek

Hello Suhas

Hello Suhas,
I agree presence detection does not require resolution.

6 feet is diameter of loop.(usually 14-18 AWG cable used with 5-6 turns)

Usually inductive sensor buried in ground can have sensitivity up to 1 m.It senses front axle or engine of the car.( its inconvenient to install and implement)
What i am thinking is to use the LDC inductive sensor and install in back side of parking slot(facing towards the car) as
the car approaches the sensor will sense car(rear wheel/silencer etc.)

For my application 20-30 cm is sufficient to detect the car.

regards,
Abhishek

Abhishek,

I am sorry I misunderstood the induction loop and inductive sensor.

Yes, inductive sensor can definitely be used in this application. However, the challenge might be to get enought eddy currents (coupling) in the target (car in this case). You can verify this by using LDC EVM and attaching a larget coil as sensor.

However, capacitve based sensing such as FDC1004 and FDC2x1x might be more suitable for proximity detection. You can find the links to them below:

http://www.ti.com/product/FDC2214/quality

http://www.ti.com/product/fdc1004

-Best Regards,

 Suhas R C

Hello Abhishek,

Could you please provide a bit more details, so we can support you the best?

1. How much space do you have for a sensor?

2. Do I understand correctly that you will have a tower of some sort, on which the sensor will be mounted?

3. Can people be in the vicinity of such tower, and what consequences if a person is detected instead of a car?

4. Exposure to the elements (Rain, snow, dirt etc)

Hello Evgeny,
1. Lets say if we have parking space, sensors will be mounted backside. For now space is not an issue.

2.Yes, we will have tower on which sensor will be mounted.

3.We can also use ultrasonic or IR sensors which can detect the presence. But we are going with induction sensor to avoid detection of person or animal and make system more stable as induction sensor only senses metal.

4. We will try to make some enclosure to cover it.

I will appreciate any feedback you can give at this time.

Regards,
Abhishek Kadam

Hello Abhishek,

Thank you for your explanation!

If insensitivity to a human/animal is important, then the choice of the inductive technology is the right one!
As Suhas has mentioned, to detect at 20cm, we will need a coil of comparable diameter. Then it becomes a compromise between sensing range and the sensor size - define the maximum size a tower will be able to accommodate, and then you will have your maximum sensing distance.

Please let us know if you have further questions.

Hello Suhas,

Thanks for sharing the link of software to calculate LDC inductance value.

As stated earlier WEBENCH can take input only up to 7 cm to sense target. I was taking these figures as my reference

For sensing 7 cm,

Total inductance=387.25 uH

Frequency=1 MHZ

As distance to sense is directly proportional to Number of turns and Inductance.

Hence for 20-30 cm -Number of turns and Inductance will be more.

For designing for 20-30 cm sensing range what inductance and number of turns should I take (Since its only excel sheet and not simulation).

I will appreciate any assistance you can give me at this point.

Thanks and regards,

Abhishek Kadam

Hello Abhishek,

I would target a coil 30cm diameter (or larger, if possible, for highest sensitivity) with ~5 turns.

Hello Abhishek,

As Evgeny has mentioned, sensor coil of 30 cm diameter should be sufficient to detect the target.

I will do my calculations and get back to you with suitable numbers for your application.

-Best Regards,

 Suhas R C

Hello Abhishek,

I have made some calculations with outer diameter of the PCB coil as 40 cm. Please find the values below:

LDC1000 is more suitable for this application. Please let me know if you need additional information.

-Best Regards,

 Suhas R C

Hello suhas,
I really appreciate your help and support. I will start making it and will let you know if this works for this kind of application.

Thanks and regards,
Abhishek

Hello Abhishek,

Cheers! Yes, keep me informed.

Please let me know if you need any additional information.

-Best Regards,

 Suhas R C

Hello Suhas,

Thanks for your help for sharing the calculation for the PCB coil. In the calculation which you gave have D_out=400mm. 

Again due to some size constraint, I made it 200mm and increased number of turns which is now 100(earlier it was 45 )

Other then that all values remains almost similar i.e. total inductance,self resonance freq, Coil fill ratio etc.

I hope this small changes are fine with the design calculation you did and will not make big changes to detect the metal presence.

Thanks and Regards,

Abhishek Kadam

HI Abhishek,

I would do only 5 turns so that the coil would be compatible with LDC1612. This IC will give you the highest sensitivity.