Hey, I am currently working on a project focused on designing a smart ring for sleep and activity monitoring and I am in need of a small-sized microcontroller board that can be integrated into the smart ring. It musst suport wirless charging to the smart ring without need to a USB to geht charging.
Can somebody help me with this issue please?
Best regards
Ali
Hi, @al-janabi
Welcome to the forum.
How small/big is the ring?
Can you please tell us your electronics, programming, arduino, hardware experience?
Thanks.. Tom... 
It's extremely unlikely that you'll find any off-the-shelf board that will "just fit" into a ring!
For standard Arduinos, look at the Nano 33 BLE Sense:
You could use that to prototype your ideas, but actually fitting it into a ring will require custom design - and pretty specialist design at that, being able to achieve the necessary level miniaturisation, plus wireless connectivity & charging! 
also consider the Wemos D1 mini ESP32 - the ESp32 microcontroller has onboard WiFi, Bluetooth classic and BLE
Hello Tom,
the ring is between 8 to 10 mm broad for sleep and activity monitoring. I need Sensor and Microcontroller that can be integrated into this small ring.
But ist possible to find a sensor and microcontroller for this reason? I have to give my projektwork in one month.
Is this a school/college project, then?
Again, you're highly unlikely to find anything off-the-shelf - unless you can find a complete, ready-made ring with electronics.
And one month is unrealistic for a custom design.
I think you need to be talking to your teacher/tutor urgently ...
As @awneil says, you can be quite busy prototyping everything even if it ends up being quite larger than a ring.
Any professional doing a ring would, no doubt, start with things that were very much larger and decidedly not ring-like.
So do that, and add hand waving about what the next steps might be and who and what might need to be involved.
A honking bracelet might be within your grasp, but even in that case it woukd make sense to prototype with no aim to achieve the final mechanical concept.
a7
assuming devices meet the system requirements one of the things you need to consider and report on in your project report is device availability and cost
in the UK the Nano 33 BLE Sense is around £60 the ESP32 D1 mini is around £6
It says it's based on a Nordic nRF52832 - so maybe you can hack it ... ?
Plenty of boards available for prototyping; eg,
But the D1 doesn't have any sensors - so don't forget to factor that in ...
good point if any of the alternatives have suitable sensors onboard
It is a college project. I have only to design the smart ring with the eagle and Fusion 360, this means i don't have to make it in the reality. It is only simulation thing.
so why are you asking about boards, then?
A good question! Because the ring musst be then designable in the reality when it have to be realized in the praxis. My Professur told me that the assembly like accelerometer, microprocessor, Battery and Bluetooth unit musst be real. This mean i can't to choose wrong assembly to design the smart ring with the software.
I don't understand yet if i need to look at the massen of assemblies to design the smart ring?
In reality, the really cool things don't use anything you are going to find on the shelf anywhere.
They a chock-a-block full of custom stuff designed for the use case.
Easy (practical, affordable) when you are planning to make a few million of something.
Have your professor drop by here, we'll tune him up.
a7
These are some of the smallest microcontrollers: Top 5 Smallest Microcontrollers.
Not sure what kind of sensor you need and will fit in the ring. And don't forget that you need a battery and charging circuit.
Not necessarily. The Ali one above uses a standard nRF chip.
and you're somehow going to have to design a bluetooth antenna in there ...
to avoid the problem would recommend using a module with built in antenna
e.g. recently used a Microchip BM71 in a wareable product