Webinar: Integrating Wireless Charging05 September 2018
The Webinar, titled “Integrating wireless charging” focused on how to integrate Wi-Charge wireless energy modules into products. It featured Ori Mor, Vice President Research and Development and Yuval Boger, Chief Marketing Officer, both from Wi-Charge.
The agenda included:
- Identifying the best candidates for integration.
- Hardware and optical considerations.
- Description of sample integration with a smart door lock with a Wi-Charge receiver.
Yuval Boger (CMO): Hello everyone, and welcome to the Wi-Charge Wireless Power Integration Guidelines webinar. This is Yuval Boger, Chief Marketing Officer for Wi-Charge. Today I have with me Ori Mor, VP of Research and Development.
Today we want to talk about what makes a good candidate for integrating wireless power. We want to talk about the hardware requirements, what you should think about when integrating Wi-Charge wireless power into your device, about design considerations, we want to do a case study and talk about a device we’ve integrated, and then we also want to do Q&A.
Ori Mor (VP R&D): It seems wireless power is something new, and when we say wireless
power, we mean over-the-air wireless power, wireless power to a few meters, or feet away not the proximity pads that sometimes people mix with wireless power. Everyone wants wireless
power, but the question is, can Wi-Charge power anything? Or, are there any limitations?
Unfortunately, we cannot power everything that we would like to power. At the moment, we cannot power electric cars because it requires very high power and it needs an ecosystem
to work as we imagine. And we cannot power the router in the outer room because there is no line of sight.
Certain devices can be powered and certain cannot be powered. There is the oven in your house, we would not be powering it. It would be probably too expensive. But there are many types of products that we can power. Mobile devices, IoT devices, and a lot of consumer electronics devices that we can power. Actually, the pain that we endure daily are by devices that Wi-Charge can power.
So, let’s go over and see what kind of products we would be able to power.
One thing that we need to consider when powering something is how much power it needs, and we will address this thoroughly in a few minutes. We are focusing on devices
with the average power requirement ranging from 10 milliwatts to three to five watts. We will explain why 10 milliwatts and why three to five watts, and basically what is average power because this is not something that some people would probably be aware of.
The other thing is, if you’d like to deliver a substantial amount of power, which usually is not needed but, we have been exploring this as well. Wireless power is a line
of sight technology. You need to have line of sight most of the time between your charger and the device that’s being charged.
You also need a sufficient ROI. If you have a better solution like a battery or with power cords, you wouldn’t need wireless power. For us, it’s even easier, and I’ll explain in a minute why, if the device is already battery-operated or if the device is already powered by a USB.
Let’s dive in a bit.
Why is it important that the device is already battery operated? Because people who design a
device that is battery operated, they have already done some optimization in terms of power consumption. When you have a device that is plugged to the wall constantly, the engineer
that designed the device is not aware or will not do any optimization on power requirements. When the device is designed to be battery-operated, and we know that we do not want to replace batteries all the time. It’s a hassle and it costs money. The designer will be aware of how much the device is consuming. We have encountered developers, quite a lot of developers that say “The average power?” or, “Idle power?” They say, “Who cares how much it consumes?”, “It’s constantly on.” You can see the same devices by the same company that is doing the same thing. One is battery operated, and one is not. The idle power and the power consumption for the same device is different. That’s a matter of awareness.
Since, for us, it is important how much power the device consumes, the battery-operated devices, it’s highly likely we can power them without any effort. The other thing is a bit less important, but it’s always a happy surprise.
If the device is already USB powered, then our output is USB compatible and we simply plug and play and it takes seconds to power it. That’s what makes integration even easier.
Let’s go to line of sight. Line of sight is probably the most disturbing downside of wireless power, but it cannot be done any other way. We use directional light to deliver power. This is why we can deliver 100 times or 1000 times more power and more efficiently
than any other microwave technology can deliver over the distance to a small receiver that actually can fit into a consumer electronic device.
That’s the reason why it is safe, and that’s the reason why it is efficient.
But it has drawbacks. Since light travels in straight lines and it cannot penetrate opaque objects, there has to be line of sight between the transmitter and the receiver most of the time. It doesn’t have to be all the time. It has to be enough time during the day so the device will get enough energy. It stores it in an internal battery and uses it when needed. That’s one very, very critical consideration when you consider if this device a good candidate to be wirelessly powered, is whether the transmitter and the charger and the client device can see each other.
Yuval: One thing I just wanted to add, Ori, we published a blog post, sort of a trick question, and asked, “Which wireless power technology “can charge a phone in your pocket?” And it’s a trick question because the answer is: “no wireless power technology can charge a phone in your pocket”, and the reason is that RF cannot charge a phone, period. In your pocket, out of your pocket, away from your pocket, in your front pocket, in your back pocket, it just doesn’t work. Line of sight is a limitation of infrared technology, so if the phone is hidden in your pocket then, for the time being, we cannot charge it.
Ori:I have one correction. RF can charge a phone in your pocket, it would simply take
more than 10,000 years.
Yuval: So, practically, cannot charge a phone.
Ori: Yes. Everyone wants their phone to be charged in their pocket, but as you said, there is no
technology that can do that.
This drawing is simply an illustration that depicts what we spoke of earlier. If there is line of sight, it is easy to charge. If there is no line of sight, if there is a constant obstruction,
then it’s not an option. If there is a line of sight most of the time, for example, if you have a
device, a transmitter on the TV and then a rear speaker on your back wall and people are walking in front of it, that’s OK. Most of the time, there is line of sight.
The next critical aspect of what we are going to be able to charge is how much power a device consumes. I can say that before starting to work on wireless power at Wi-Charge, I didn’t know how much power devices consumed. It’s not something a common or even a technical person would be aware of, and it’s tricky.
This is a bit technical, but it’s important.
We are focusing right now on devices that the average power would be in the range of 10 milliwatts to three watts. Why 10 milliwatts? Because below 10 milliwatts, we can power it, but batteries may be a good enough solution. Above five milliwatts, above 10 milliwatts, no matter how you look at it, you would either need huge batteries or you would either need to replace them too frequently, so the hassle becomes a killer to the app.
Above three watts is, at the moment, something that we decided not to focus on. Our work method is certainly above three watts, and I think that very soon we will be at 10 Watts, but we have enough applications that enjoy this range, and this is currently our focus.
However, this is average power, not peak power, and we need to explain the difference between average power and peak power. Devices do not consume the same amount of power all the time. Let’s say you have a smart speaker, a personal system speaker that is on your table and waiting to be activated. While it is waiting to be activated, it is in listening mode, in idle state. It does not consume the same amount of power as when you ask the device to play a song or something like that. While we can charge the device, let’s say, all the time, the power it’ll be consuming during the day may vary, and what we are interested in is the average power.
You can think of power or energy like a pool. You have a hose that is filling the pool with power, with water, with energy, and from time to time, as someone drains the pool in
an arbitrary amount of power, it can be low, it can be high, but as long as the water level in the pool is not empty, you can supply the required power for the device.
We will give a numerical example for something like that.
Yuval: Before you continue Ori, I usually explain that this is like the water tank in the toilet. You can fill it up slowly over time, but then when you need to flush the water, you can
get a lot of water quickly. We’re working with a customer right now, I won’t disclose the details yet, but this is a customer where they have a motor and the motor needs about
15 watts to operate, but fortunately, it operates only several times a day, so they’re charging the battery, as you described, when it’s not operating, and then there’s plenty of power to use when it is. Let’s run through the example that you were discussing.
Ori: OK, it will be a numerical example, but a simple one so we won’t be too confused about it. Let’s look at the pair of rear speakers that can be used for home theater, and for the sake of this example, let’s say that each speaker needs four watts while playing music, meaning a total of eight watts. What is the average power? What do we need to power these devices wirelessly, assuming they have a rechargeable battery inside? The answer depends actually on
how much they’re being used.
If they’re being used for two hours a day, then the average power would be eight Watts times two hours, that’s the amount of energy that they would need, but divided by 24 hours. Let’s say we have 24 hours that they are constantly being charged, the daily average power would be roughly 0.66 or 0.7 Watts, meaning that if you have a transmitter that delivers 1.66 Watts, you can use those speakers two hours a day, four Watts for each one of them.
The same thing if we go to four hours a day, then we would need a transmitter of 1.33 Watts, and if we use the speakers for nine hours a day each day, then the average power
would be three watts. The example that you gave is a very good example because the motor really takes 15 watts or maybe even 30 watts, but it operates not so much, for not a long time during the day, so our very tiny transmitter can support it.
There is a video by Nissan, the carmaker. They wanted to promote a self-parking car and they used a movie of a self-parking chair, meaning a chair that, at the end of the day, you clap your hand and all the chairs go back to their place. It was a fun movie, we got two million views, and people started asking for those chairs, but the Nissan guys said, “It’s not for sale. “It was a promotional video.” What is interesting about this is that those chairs, when they move, they consume 100 Watts, but they move for a few seconds a few times a day, so even an IoT transmitter that delivers, I think, 0.5 watts, which is very small compared to 100 watts, can power a meeting room with 10 chairs easily.
This is the difference between average power and peak power.
Moving to the next section, we will talk about the hardware requirements. Since we are basically a wireless power supply, then it’s not very complicated to do the integration. The integration is divided into two sections: We need to do an electrical integration, and we need to do a mechanical integration. There is also some software integration, which, not everyone wants, but it’s an option. Basically, after you do the electrical integration, and optical integration, that’s it.
Electrical integration is quite simple. If we pass the two criteria before of the average power and the line of sight, everything becomes very simple.
Why is that? Because we are simply a power supply, a wireless power supply, but the client device that we are connecting to, it doesn’t know if the plug it receives is wired or wirelessly powered. If it has a USB input, and we are USB compatible, that’s it.
Usually, devices that are battery-operated and maybe even USB battery-operated, they usually accept five volts or sometimes 3.7, so it would be directly for the battery charger. That’s our receiver output. The device input is usually five volts. Then, the integration takes a few minutes, that’s more than enough.
We simply connect as we would the USB charger. If it’s another device that is not battery operated, it is usually working with a power supply, and then the device input
voltage usually varies. You all know your DC power supplies. They’re usually valid between
three volts and 12 volts, maybe even 24, but that’s rarely. What we do in this case is we adjust. We first add an internal rechargeable battery so we can charge it over time, and we adjust the output voltage when the power flows from the rechargeable battery to the client based on what the client needs. That’s usually a simple boost. It is called a boost converter
because it boosts the voltage from the 3.7 volts of the lithium-ion battery to the voltage that the client device requires.
OK, the optical integration is the next integration that we need to take into
account when integrating a receiver in a client device. As we said earlier, the
receiver needs to have line of sight to the transmitter, so the receiver should be
facing the general direction. It would not need to be aligned or something like that, but it has to face the general direction of the transmitter. What you see here is our current receiver. The red circle denotes the optical part, and the green circle is where the electronics is.
Basically what we need is an aperture in the device the size of the optical part. I would say roughly 15 by 15 millimeter, six-millimeter thickness or probably even less. And that’s it. The rest of the electronics can be folded into the device itself.
Once we place it, the transmitter will know how to find it. It will generate the power delivery, and the electronics will do the matching needed between our device and the client device.
It would be easier to understand what we spoke about so far, so we will go over a case
study where we embedded our receiver into a smart door lock. The smart door lock is a
very interesting product. It is interesting in several aspects. The device that we
integrated was the device with face recognition and finger ID. Some products like this
also have WiFi connectivity and video streaming. That allows people to
open the door to a courier while they’re at work or in another part of the world. You can open the door while sitting on the sofa. There are plenty of useful things to do with devices like this. The problem is that whenever there is a smart device, it is a power-hungry device. They need to be powered, and the average power is above 10 milliwatts, and it becomes a problem because they need to be frequently charged.
The way to overcome it is either to accept that you have to frequently charge your smart door lock or to let go of the features and end up with a door lock that is a keypad only.
Yuval: The problem with door locks is that, on one hand, it’s adding peace of
mind because you can have better control over who’s in and who’s out. You know, if your kid forgot his keys, you can open the door remotely with your phone.
But on the other hand, if you’re always worried that you’re going to run out of batteries and you’re going to be locked out of your home, then that’s a problem. Hiring an electrician to
run electricity to your door is also not a walk in the park. Therefore, for smart door locks
or these kinds of devices, the ability to all of a sudden deliver all the power that you need to enable these new features is really a godsend.
We’ve been speaking with door lock manufacturers and they’ve said, the number one requested feature is that when someone comes in, they would like the door lock to record and upload a three-second video so they know if it’s a neighbor or the Amazon guy or a stranger, but recording and uploading that video is really power-intensive and I don’t want to force the customer to change batteries every week.
Therefore, wireless charging, we thought, could be a great solution for that, and we made a test case.
Ori: What we see here is the integration that we did for the smart door lock. We decided to place the receiver on top. Its the red part on the left-hand side. On the bottom part, you
can see the battery. It already had a rechargeable battery, so we only needed to change the door lock cover. Instead of its original cover, we added our cover with our receiver inside it. Two wires went from the output of the receiver to the battery charger PCB. That’s the electric circuit. We also added an indicator. That’s the green LED in the middle, which was not a must, but we wanted it to display when it is charging and when it is not.
And I think, basically, that was it. The most time-consuming task was the mechanical design of the cover. Other than that, it worked pretty simple and very fast. On the left, you can see
the assembly in testing. The receiver on top, we’re seeing its transmitter, and when the green LED is on, charging takes place. On the right is the outer side of the smart door lock with face recognition and fingerprint reader. That would be facing to the outer side of your home.
Yuval: I want to open the floor for some questions, and let’s see what I’ve received. One question, you mentioned earlier a little bit about software integration. Is there anything that I need to do on the receiver side or are you providing options on the transmitter side?
Ori: Yes. There are devices like smart door locks where the functionality is pretty simple. Just get them power, and that’s it. They do not need any software integration. But there are devices that you would want to know the statistics and power that is being used by your device and their status. In this case, we provide an API, and through you can get how many devices, how much power consumed, where they are located when they consume power, et cetera, et cetera. That’s mainly for applications like in public spaces where the business owner
would like to get his business intelligence about how the service is being used.
Yuval: It’s almost like managed WiFi versus unmanaged WiFi. At home, I may have a WiFi
router and I don’t need to worry about statistics, but if I’m running a coffee shop, I want to see how much bandwidth, who is logging in, what kind of applications are being run, and so forth.
The second question, you mentioned about the receiver having to be roughly in the
direction of the transmitter. Is there an alignment process that I have to worry about, or is the system pretty much plug and play?
Ori: The system is plug and play. The receiver entrance meter has a field of view of roughly a cone of 100 degrees, so if it is pointing not even in the general direction, you can imagine the cone of plus-minus 50, plus-minus 45 degrees, and as long as it’s within this cone, the transmitter will find on its own the receiver and the charging will take place.
Yuval: And how long does it take for the transmitter to find the receiver? For instance, if I have
a hospital environment and I have a patient call button that I want to charge and a new patient walks in the room, how long does it take the transmitter to find the receiver? Is it hours, is it days, is it minutes?
Ori: Two seconds. The current design supports two seconds. It is an overkill for all of the devices that we are currently handling. It is pretty easy to make it even faster.
Yuval: I must tell you that as the one doing a lot of demos, two seconds is great, because you don’t have to wait for the charging to start. But I agree, if you’re installing this in a smart building and the devices are fixed, and even if it took a minute for it to find all the devices, that’s negligible for a system that remains on.
I want to point the audience at a couple other resources. We have a demo site. It’s called Will-It-Charge.com
It shows a whole bunch of demonstration videos. For instance, we just put up game controllers and wireless keyboards. Even just light sources. If you want a completely wireless light, you could see how that works. Then, our contact information, the website,
our Twitter handle @WiChargeLTD.
We’d be more than happy to hear from you with technical questions or partnership requests and so on.
Thank you, Ori, and thanks everyone for participating.