EMF detector with a lot of noise

Hello,

I was trying EMF tutorials on the internet, such as this, or this one.

They are pretty straight forward, so I did the same wiring and uploaded the code except for the resistor value. I've tried 1M ohm and 10M ohm.

The problem is the analog value only shows a lot of noise, and I cannot see any distinguishable value for mobile phones. I can see big values only when I grab the antenna. When I read the analog value from the antenna (0-1023) it just shows random values 0-100 around something, and nothing big changes with smartphones. Therefore if I write the value to the LED, the LED keeps flickering no matter the antenna is alone or approaching some electro devices.

Ideally, I'd like to detect inductive power RX on smartphones. Please let me know if you have any suggestions or hint for this situation.

What do you think EMF is other than "noise"? For inductive power you need a loop to detect a magnetic field.

Paul

The reasoning behind calling the output as noise is I was getting consistent big values even in an empty office room. I will definitely try to make a loop at the end of the antenna, Thanks!

eloqy:
The reasoning behind calling the output as noise is I was getting consistent big values even in an empty office room. I will definitely try to make a loop at the end of the antenna, Thanks!

One end of the loop must be connected to system ground, otherwise there is no way to pick up the magnetic field.

Paul

To detect emissions from cell phones, you need a tuned loop antenna. Examples

I've tried putting a loop antenna (the coil in the wireless charging TX) but didn't work as well. I guess it's a more fundamental issue not just for detecting smartphones but electronic devices.

What frequencies are you trying to receive?

Hello,

I am trying to figure it out to detect wireless power receiver on smartphones to make a wireless charger.
The reason I need to detect the receiver is that I will adjust the position of smartphone for efficiency.
so my plan is to make a grid of detecting antennas and calculate the right position of the receiver coil.
To start, I've tried a lot of tutorials of EMF detectors like this but it didn't go well.

The question is if this plan is in the right direction and want to know the right way to detect the inductive power receiver. Technically it doesn't need to be a TX since I already have it.

(I've posted a question in another category yesterday why it is not detecting well. It shows just a consistent random value while detecting in the air. There is no value change whether there are devices around it or not. If you have any idea about this, more than welcome.)

The only way to detect the existence of a receiver is by detecting the power it draws from a matching transmitter. This requires expertise in electronics and radio frequency apparatus.

eloqy:
Hello,

I am trying to figure it out to detect wireless power receiver on smartphones to make a wireless charger.
The reason I need to detect the receiver is that I will adjust the position of smartphone for efficiency.
so my plan is to make a grid of detecting antennas and calculate the right position of the receiver coil.
To start, I've tried a lot of tutorials of EMF detectors like this but it didn't go well.

The question is if this plan is in the right direction and want to know the right way to detect the inductive power receiver. Technically it doesn't need to be a TX since I already have it.

(I've posted a question in another category yesterday why it is not detecting well. It shows just a consistent random value while detecting in the air. There is no value change whether there are devices around it or not. If you have any idea about this, more than welcome.)

I think you need to have more schooling. Wireless charging is by inductance, like a transformer. Not RF like in a transmitter and receiver.

AS far as efficiency is concerned, closer is always better.

Paul

duplicate thread

@eloqy

TOPIC MERGED.

Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

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@ballscrewbob Sorry, I wanted to change the category of the question (and didn’t know how to change the category of the already posted thread) and thought the questions are related but different.

ballscrewbob:
@eloqy

TOPIC MERGED.

Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

Continued cross posting could result in a time out from the forum.

Could you take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum.

aarg:
What frequencies are you trying to receive?

@aarg I am trying to get 100Hz - 200Hz

Let google be your friend.

As you will see this is a common question with lots of useful info.

Bob.

The goal of the project is to make a servo motor adjust the position of smartphones to get the right on to the TX.
I have this product and took a look inside, and there was a grid of loop antennas to detect RX position beside the TX.
According to the responses, then should I hack the TX module and check the power changes of it?
I will attach the photo of the grid when I find it.

If I get this correct you simply want to "MAP" that charger to find the "hot spots" ?
Not too sure of the point myself but it is certainly do-able.

Some form of sensetive NCV device would do that.
The Arduino is quite sensetive to emf so it would maybe be possible to simply place a grid pattern ove the charger and use a wire to an analog pin to act as a pickup.
Then simply map the numbers to the grid.

From that a pair of servos could also be mapped to home in (minus a phone size offset) to shuffle the phone to the optimum hot spot.

Am I on track or wildly off base ?

The problem is that you are making so many assumptions about the system without researching it. One is that the phone is found by something that it's emitting... this may not be as straighforward as you, again, the big word... assume.

Instead of guessing around, you need to focus on the Qi specification and do some simple Google searches like I did. You would find interesting things like,

"Communication is unidirectional from the power receiver to the power transmitter via backscatter modulation. In backscatter modulation, the power-receiver coil is loaded, changing the current draw at the power transmitter. These current changes are monitored and demodulated into the information required for the two devices to work together."

You will get a lot more help here if you do some heavy lifting yourself.