Wireless Power for IoT Sensors2022-10-03T17:52:33+00:00

Wireless Power for IoT Sensors

To Qi or Not To Qi: IoT Sensors Introduction

NuCurrent has been driving the wireless power industry for over a decade, launched more product categories into mass production than any other company in the world, and developed a global reputation for technology innovation with over 150 patents and many contributions to global standards bodies like the WPC, Airfuel, and NFC. NuCurrent sets customers up for wireless power success by posing five essential questions to determine which wireless power transfer method will be most effective for IoT sensors.

While Qi-based (inductive) charging is the best-known method of wireless power transfer, there are several other options for product developers to consider. In the To Qi or Not To Qi: Introduction video, NuCurrent explores and defines the different wireless power transfer methods available and details key terminology and concepts along the way.

(logo swoosh) Good morning and good afternoon and good evening to everybody from around the world joining us today. My name is Mike Harmon, I'm the Director of Marketing at NuCurrent and today I'm once again joined by my esteemed colleague and Senior Field Applications Engineer, Jason Luzinski for a topic that is clearly a popular one, what we call To Qi, or Not To Qi. I'd like to take a minute to address why I think this topic is so popular and why NuCurrent is a really good resource to address it. Wireless power and wireless charging means different things to different people. This is an emerging and high growth industry with a lot of different technologies and techniques and terminology and so on. So, for someone walking into this or even someone who's spent a little bit of time with it it can be pretty confusing and that's where NuCurrent comes in. We've been driving this industry for over a decade and we've launched more product categories into mass production than anyone in the world. And we've developed a global reputation for technology innovation with over 150 patents, granted (indistinct) many major contributions to global standards bodies like the WPC and AirFuel and NFC. We've developed a center of excellence with over 50 engineers representing RF mechanical, electrical, and software disciplines all serving major challenges in wireless power. And we do so in a way that we aim to be easy to work with and customer centric, which has qualified us to be among other things and an NXP Gold Partner. And ultimately we're driven to be the world's go-to resource for wireless power, which is why we put on programs like the ones that we have today. As we get started into the meat of this, we're really gonna dig into wireless power over the next hour and before we do we ought to review some important concepts excuse me, and terminology. So first on the left-hand side of the screen, we're gonna take a quick peak at transfer methods and the different types of methods of power transfer that are gonna be applicable for the conversation today. The first is low frequency, which is operating at 110 to 220 kilohertz via magnetic induction. And so Qi, which is, you know, the most well-known standard and method of power transfer is regarded as a low-frequency method. So we wanna make sure everybody understands that. Also Apple's new MagSafe protocol is a low frequency at around 360 kilohertz. Moving on to NFC which is a relatively new transfer method for wireless power operates at 13.56 megahertz and employs magnetic resonance. Similarly high-frequency using magnetic resonance is at 6.78 megahertz. We've got a high frequency solution as well that tends to map to what AirFuel has done as well as NuCurrent through our NuEva Development Platform. The next transfer method we refer to as a hybrid which is really sort of application specific but it employs both low frequency and high frequency. So inductive and NFC for kitchen appliances and the cordless kitchen through the Ki standard. And then lastly, the RF method of transfer which operates around 915 megahertz to 2.4 gigahertz using radio frequency power transfer. And so these methods are gonna come into play as we go through the different product examples that we have. But before we jump into those, there are some definitions and some terminology that I would like to have Jason walk us through so that everybody's aware of these terms as we talk about them through the products that we'd go through. So Jason, can you walk us through the concepts of magnetic induction and magnetic resonance for the audience? Yeah, sure. So magnetic induction is what we coined low-frequency technologies as we are operating like an air transformer where we are relying on coupling to deliver majority of the efficiency as we're trying to harness as many of the flux lines or the magnetic field lines going from the transmitter to the receiver. Magnetic resonance is a blend of a magnetic induction but it also has a little bit of more RF components attached to it such as energy storing items such as a tuning network that allow us to utilize and store energy to not have to rely on coupling as much. Magnetic resonance technologies are in the high frequency range of the NFC or 6, 7, 8, 13.56 megahertz. The next definition we are going to define is going to be antenna and coil. So we are gonna be talking about our RF wireless power technologies which rely on electromagnetic fields as opposed to just magnetic fields. So antenna will relate to something like a Bluetooth antenna, something that is able to harness the field similar to the RF technologies of 915 megahertz to 2.4 gigahertz, and the coil will relate to the inductor that we use for wireless power. The third definition we're gonna cover is coupling and mutual inductance. So this is related to the magnetic technologies. Essentially coupling is the ability of a receiver to capture a percentage of the magnetic flux that is created by a transmitter. This is usually on a scale from zero to one where one is you're capturing all of the fields and zero is capturing your none of the fields. Mutual inductance is the interaction between your receiver and transmitter coil. So essentially you have windings on both sides that are creating an inductance, the transmitter creates a field that generates a voltage on the receiver windings and that receiver winding actually, when you generate that voltage creates a current which inherently has an effect back on the transmitter. So, by understanding that value, you can kind of estimate the amount of power you're able to transfer over a certain area. Third item that we are going to define is foreign object detection. This is kind of an industry standard term where we're talking about as you're transferring power from a transmitter to a receiver and someone places let's say a coin or a key into the field, that is considered a foreign object, something that shouldn't be there. And we wanna be cognizant of these items because they cause safety issues and degrade performance of the system. The next term is charging infrastructure. This is related to the global standards that we have out currently, that is related to AirFuel to Qi to Ki and basically in terms of what is currently available the global leader in charging infrastructure is Qi. You know, all the pads that you see laying around the tables to charge your iPhone, or your Samsung phone, you know, those are related to the Qi charging infrastructure. And there's lots of great companies that are integrating these things into public spaces, so that as you walk around, you don't need to bring your charger anymore. you can just place it down and be able to charge, And the last term that we are going to define is proprietary solution or let's say closed ecosystem. All of these technologies can be developed into a proprietary solution for a specific customer. Now, if we talk about a larger ecosystem, such as Qi that is more charging infrastructure. So we want to create that separation between the two to ensure that you understand in certain situations where, you know, you really don't care about utilizing, for example, the Qi standards, but you want to be able to create your own ecosystem within a family of products, that's how we delineate the two. Jason thanks for running through that. The next slide here is just one of the things that really helps us focus. The session that we have today with some really useful questions and coming from outside the industry, this was one of the things that really helped develop my own understanding of how to map solutions to products. And there are two real breakthroughs I think in having these questions. The first is that we've got these five really smart questions that help quickly eliminate certain options and shine a light on what might be the best solution candidates. And then the next part about this is that based on the nature of the product, whether it's industrial design or its use case or the power levels, some questions are better asked first in this process than others. So we actually give ourselves the flexibility to do that. And as we go through the products that we have today we are gonna see that we approach all of these questions but we sometimes do them in different orders based on what we know about that product. So Jason, let's go through these questions and talk about the rationale for why they matter. So why would someone care about this first question? What is the size of the product and size of the antenna required when it comes to wireless power? So, this is one of the questions that I like to ask is because the size of the product will automatically dictate the maximum size of the receiver core. This will right away eliminate certain wireless power technologies due to the need for specific resistance and coupling characteristics to hit necessary thermal and user experience specifications. Great, so moving on to question two, what is the coil-to-coil distance and how many receivers need to be charged? So, wireless power requires appropriate mutual inductance which is a function of the inductance of the transmitter receiver and coupler. If the charge distance is greater than four to five millimeters, or requires a larger XY offset, it may be necessary to move to a high frequency technology as these do not rely on coupling as heavily as low frequency technologies. With this in mind, it is possible to eliminate certain tech paths based on the unique attributes of the product. Additionally, if there's a desire to charge multiple devices on a singular pad, high-frequency and NFC is usually the desired path due to the ability to operate under low coupling conditions. Great, so the first two are really about size and antenna related, the third one says, does the product need data transfer capabilities greater than 10 kbps? What's up with that? So, wireless power technologies have certain data transfer capabilities. Low frequency technology such as Qi was originally designed to be solely for power and the low frequency of operation limits the total data transfer through but about two kilobits a second from the receiver to the transmitter and on the order of bits from the transmitter to the receiver. NFC comes from a data background and with its higher frequency of operation at about 13.56 megahertz, allows up to 848 kilobits a second throughput. High frequency also supports in band communication up to about 10 kilobits a second. So, if that is a key requirement of a system, this question can be used to eliminate certain technologies. All of these technologies can potentially use auto band communication such as BLE, or ZigBee or a similar scheme, but this usually increases the cost and complexity of the system.
Great, so the next question,
do you need this product to be interoperable with existing infrastructure such as Qi?
This is an easy elimination question.
As of right now, there are only three viable charging infrastructure standards, Qi, NFC, and Ki. So if your product requires the use of an existing Qi charging pads, or wishes to use NFC data infrastructure, you can easily remove certain technology.
Perfect and then the last one,
what is the power level required to power or charge the device?
So power level is usually
one of the first questions you can ask to eliminate certain technologies. If the powers required is greater than three watts, you can immediately remove NFC and RF. However, if the power requirements is less than three watts, you know, you may need to start with a different question and to kind of touch on these five questions, the order that I asked them in is based off my previous experience being in the industry for six, seven years now and applying these questions to the different use cases of products that we see coming in. Wireless power is an interesting blend of mechanical, electrical, RF engineering, in addition to helping shape the industrial design and user experience of a product. So depending on the product that you're looking at you may have a different approach of how you ask these questions for a project that you're looking at. However, as we go through the presentation, I'm gonna give you an insight kind of how I approach this, but I urge everyone to look at the questions and understand what is really key and important for your product and the experience that you're trying to bring your end customers. (logo swoosh)

Best Wireless Power Transfer Methods for IoT Sensors

IoT sensors are low-power devices that gather data to inform calculated decisions. Each IoT device has individualized requirements from the sensor, such as power transfer levels, data transfer, and sensor sizing restrictions. The special requirements eliminate the possibility of a one-size-fits-all solution, resulting in the need for a custom wireless power solution. In To Qi or Not To Qi: IoT Sensors, NuCurrent reveals why RF and NFC are the best wireless power transfer methods.

This next one is a little tricky.
It involves IOT sensors that you might find

in an industrial setting or retail setting.

There's some different options here,

but each of them has some challenges.

So can you please walk us through your thinking

of these questions for IoT-type sensors?

So when I think of IoT sensors,

I think of the plethora of different devices

that we have placed all around, you know, the environment.

So the first question I ask myself is,

"What is the size of the product?"

And "What is the size of the antenna required?"

You know, there are possibilities of IoT sensors

that you place within a grocery store

that are on the shelves, that are the sensors,

that are, you know, measuring people capacity,

or whether items are still on the shelf or stocked.

Those tend to be relatively small and fixed in location.

I also think of IoT sensors as some of the things,

temperature sensors or impact sensors

that you place within packages.

So those have, you know, a larger size

compared to the first types of sensors that we talked about.

The third type of IoT sensor that I'm kind of visualizing

in my mind is something like a SmartLock.

The ability to open your door via an app

because your lock on your front door is connected

to your home network.

And you can basically let people in or give a code

and use that functionality.

So when I think of IoT sensors,

I think of lower-power devices,

but with a larger breadth of sizes.

From that, I kind of think RF and NFC

are the appropriate technologies to approach this

based off the power levels and the size requirements.

Great, so that's starting to rule out

the low frequency or Qi-option,

high-frequency, and the hybrid.

So as we zero in on RF and NFC as options,

we started to see a couple of yellow boxes

in each of the columns for question two and three.

Can you walk us through those?

Yeah, of course.

So this is kind of where both RF, NFC are viable options

but they have trade-offs in different places.

So from a power level standpoint,

RF really can only supply a couple of milliwatts of power

over the larger distance, where you find the benefit

of RF wireless power happening.

As a result, the IoT sensor in order to get anything

greater than a couple of milliwatts would have to be

right next to the transmitter.

Which kind of eliminates the purpose of that RF,

let's say, user experience.

With NFC, I give it a plus because we are able,

in a close coupling position, deliver up to 3 Watts

of power to the device.

So if your sensor that you're looking to power

is a little bit more power-hungry,

NFC definitely has the edge up here.

If your IoT sensor is on the lower-power scale,

think a couple of milliwatts,

and has relatively fixed position,

I would say RF is, you know, a potential solution.

So, on this question, I give NFC the thumbs up

due to the capability.

Great, so some complex decisions there

and sort of a case-by-case walkthrough

as folks evaluate this.

But clearly, RF and NFC have their different pros and cons.

Take us through the next two questions, Jason,

in terms of how these might play out

in the thinking process.

Of course, so the next question I asked myself is,

"What is quote unquote distance

"and how many receivers are you going to need to charge?"

Kind of going back to that first question

about the size of the product.

RF has a big, you know, let's say, it has an advantage here

relating to very small, low power devices

but multiple of them within all locations.

So if you picture a Walmart warehouse,

where you have sensors that are measuring

the amount of goods within a specific shelving unit

or the temperature across the entire warehouse,

these fixed extremely low power devices

having an RF solution allows you to charge multiple devices

at once at these low power levels.

So from a implementation standpoint, it makes quite a bit

of sense to use RF in this kind of technology.

With NFC, you know, we're talking about close coupling.

The devices have to be relatively close to each other.

So that's why I kind of give it a minus

because it is kind of forced to be in one

kind of orientation compared to RF.

But it does give you the higher power levels.

So in this specific topic, I give RF the plus

specifically for the use case of the product.

But NFC is a close second.

Great, and so now we've kind of handled

the pros and cons and trade offs of these two solutions.

When you look at question four, question five,

it sounds like the prospects are agreeable for both.

But is there anything you'd like to mention

about those two questions for the audience here?

Yeah, of course.

So from an RF standpoint, there are proprietary ecosystems

being created by OSSIA and Energous to be able to,

let's say, enable these types of warehouses.

If you're looking for something that is more ubiquitous

on a global scale, unfortunately, it's not there.

You are going to have to state

that this proprietary ecosystem created by these companies

in order to get that, let's say, true RF experience

that you're looking for.

With NFC, again, you're not getting

the larger charts systems but you have the ability

to use quite well-known

and well-established technology within NFC.

Both from a charging aspect as it's, you know,

being ratified from the WLC,

wireless charging for NFC form

and also from a data standpoint.

So if you're looking for something

a little bit more proprietary and enclosed,

RF might be appropriate solution for you.

If you're looking for something that can utilize

NFC technology from a data and a charging standpoint,

NFC is obviously going to be the path for you.

And then question five, depending on the data requirements,

nice thing about RF is you can get a continuous data stream

going on a very regular polling pace

because you're usually connected

to your IOT sensor consistently.

Because you have to power it and you can transfer the data

over the RF link.

With NFC, it's more of a tap to pair or, you know,

applying your device to a sensor to extract data from it

but also potentially give it a charge back

or enable some additional features.

So the use case is a little bit different.

RF definitely has a benefit for continuous data.

While NFC allows you to implement and provide more power

to get additional features or retrieve diagnostics

or provide, you know, programming feature to it.

So both have their benefits here.

So that's why I give them both a thumbs up.

Sure, Jason, thanks for walking

us through that.

It looks like, you know, depending on the case,

depending on the use case and the application,

these are two areas that you want to explore on the RF side.

You'll see offerings from OSSIA, Energous, or Powercast even

on the RF applications.

And then on the NFC side, you know, Nucurrents

leading the way with our Nueva and a (mumbles) platform.

So thanks for walking us through this one.

And we'll move on to the next.

(Outro music)

5 Essential Questions

  1. What is the size of the product and the size of the antenna required?
  2. What is the coil-to-coil distance, and how many receivers need to charge?
  3. Does the product need data transfer capabilities greater than 10kb/s?
  4. Do you need this product to be interoperable with existing infrastructure?
  5. What is the power level required to power/charge the device?

Best Wireless Power Solution

NuCurrent’s NuEva NFC platform delivers a premium wireless charging solution faster, with industry-leading performance and less risk.

Best Wireless Power Solution


  • Greater spatial freedom

  • Multi-device charging

  • Thin, efficient coils for small electronics

  • Large component ecosystem

Is Qi Charing for Laptops the Way to Go?

Qi-based (inductive) charging is the most popular form of wireless power, and for good reason. But there are many more power transfer methods to consider when deciding which is best for your device.

In this 60-minute session, NuCurrent will look into the different wireless power transfer methods available and walk through the tradeoffs that come with each method, followed by a recorded Q&A session.

The Power to Get to Production





QI: 15W

WHOOP mobile


Want to discuss a
NFC or custom low frequency solution?

Ready to discuss a premium wireless charging experience for your product?

Go to Top