Tuesday, June 19, 2018

Can smart locks become smarter?

Smart door locks allow intelligent locking and unlocking of doors. Unlike the old mechanical locks, smart locks add new features. Some locks include an electronic keypad. Others allow you to control the lock from your phone via Bluetooth or WiFi. Some vendor design locks that include bio-metric security such as fingerprints. Others add face recognition cameras.

There are two key issues with smart locks: power consumption and battery life. These issues are, of course, related.

Power consumption is an issue for the manufacturers. Power consumption limits the features that can be added to the lock. For instance, a vendor might want to upload video from the camera to the cloud. But, recording and uploading drains the battery and shortens battery life.

Battery life is a consumer issue. If you forget to replace batteries, you might find yourself locked out of your own home. Some vendors offer a +9V battery plug for emergency operation. If you’re one of the rare folks that leaves home with your keys, phone and a +9V battery in your pocket, you are all set. But if not, the +9V connector does not help you. Other vendors offer a solar cell that can charge a bit off the lamp function in your phone. Innovative, but is it worth it? Even if you remember to replace batteries, it is not convenient. Technology should make our lives easier, not add maintenance chores.

Instead of batteries, you could wire the lock. This would entail routing electrical wires through the door. This might be a difficult or an expensive process.

Is there a better way?

By integrating a wireless power receiver into the lock, batteries are no longer a problem. The lock receives all the power it needs to enable new features such as video recording. The manufacturer can stop worrying about power budgets. The end customer never needs to replace batteries. Wireless charging eliminates the trade-off between functionality and battery life. Customers can get both functionality and convenience. And they don’t need to carry a 9V battery in their pocket.

The video below shows a demo of a smart lock with integrated wireless power.

Wednesday, June 13, 2018

Honey, I Shrunk the IoT Sensors!

Ever notice that batteries take up a lot of space in IoT sensors? When you open up motion detection or other home security sensors, you see that batteries take up as much of 50% of the size of the sensor.

At the same time, we want these sensors to be as small as possible. Nearly invisible.

Companies that design such sensors face a trade-off: reduce the size of the battery (and thus the sensor) vs increasing the frequency in which the battery needs to be replaced. Smaller batteries have smaller energy capacity then larger batteries, and thus need to be replaced more often.

Is there a better way?

By embedding a small wireless power receiver inside these IoT sensors, a tiny rechargeable battery could replace the existing bigger battery. The tiny battery would provide the needed power for the sensor and would be continuously charged with wireless energy.

The result? smaller batteries; smaller sensors; reduced cost; better-looking product.

What’s not to like?

Wednesday, June 6, 2018

Is line-of-sight required for wireless power technologies?

No, but it helps.

When considering far-field wireless power technologies, the question of “line of sight” sometimes comes up. Sometimes, a straight line free of obstacles exists between the transmitter and the receiver. This is referred to as “line of sight”. If a line of sight does not exist, energy from the transmitter needs to be reflected off at least one surface before it reaches the receiver.

Is line of sight a requirement?

A mirror can reflect light very well. In contrast, a piece of foam might absorb some of the light, scatter a portion of the light and reflect some small portion. Similarly, a highly polished piece of metal might reflect RF well while foam might not. Different materials reflect, absorb or scatter energy beams to a different degree. How much is reflected, absorbed and scattered depends on many factors. Some of these factors are type of material, shape, surface quality, thickness, orientation angle, etc.

Having said all that, the absolute best that someone could hope for is that the amount of energy reflect towards the receiver is the same amount that hits the reflecting surface. That’s the ideal case. The reflection does not increase the energy. In the real world, the amount reflected towards the receiver will be lower than the amount that hits the reflecting surface. As such, it is always preferable to have direct line of sight between transmitter and receiver. When a line of sight exists, the receiver can get more energy.

Additionally, the shortest distance between the receiver and the transmitter is a straight line. A path that includes a reflection is longer than a direct line. For some technologies, power significantly degrades with distance. This could be because the power beam spreads out or because energy is absorbed in air. For these technologies, it is particularly important to achieve transmission in a straight line between transmitter and receiver.

Energy going in a straight line from transmitter to receiver is always going to be better than a path that has reflections.

Wednesday, May 30, 2018

Can public spaces benefit from Far-Field Wireless Charging?

Qi chargers are becoming popular. Based on magnetic induction, they are compatible with new Apple and Samsung Phones. Carefully align the phone on the charger and charging starts.

One area of popularity are coffee shops, hotel lobbies and other public spaces. Customers want to top off their phones while taking their coffee. They don't want to look for power outlets. They don't want to remember to bring charging cables with them.

Cafe owners also realize that charging stations promote customer loyalty and increases revenue. Qi chargers can integrate with desks or other surfaces. Thus, they don't impact the look and feel of the space.

But if the charging pad powers the phone, what's powering the charging pad?

At home, the solution is simple. Connect the pad to a power outlet and you're done.

At a public space, this is more difficult. While some tables might be next to the wall, many tables might be far from power outlets. Connecting all tables to power can be expensive. Running cables on the floor might become a safety concern. Furthermore, a coffee shop might want to join or otherwise rearrange tables from time to time.

The solution? Far-field wireless charging. Qi pads can charge the phones. Far-field wireless charging can provide power to the Qi pads. No need to install cables. Tables can still be mobile.

Best of all, today's phones are compatible with this solution. In time, we expect newer phones to embed far-field charging capabilities. For now, wireless-powered Qi pads are an excellent bridge from today to tomorrow.

Check out this 1-minute demo video to see how it works.

Learn more here

Wednesday, May 23, 2018

Could wireless charging keep an iPhone X happy?

The iPhone X has a 2716 mAh (10.35 Wh) Li-Ion battery. The depletion rate of the battery depends on how one uses the phone: idle, talk, music, browsing, etc.

The official specifications of the phone list capacity as follows:
  • Talk time (wireless): up to 21 hours
  • Internet use: up to 12 hours
  • Video playback (wireless): up to 13 hours
  • Audio playback (wireless): up to 60 hours

Let’s assume that under normal usage, the battery lasts about 20 hours, so average power draw is 0.5 Wh.

What if an iPhone X had an embedded far-field wireless charging receiver. Could it remain charged using only wireless charging? Only far-field charging: no charging cable, no Qi pad.

The benefits would be huge: the phone would appear to charge by itself. No more battery anxiety. No more forgetting to place it on the Qi pad. No more broken charging cables.

If you had far-field charging 24/7, you’d need to provide 0.5 Watts to keep the battery from draining. But for 24/7 charging you’d need wireless charging everywhere: at home, at the office, in the car, and so forth. Utopian, but unlikely.

If you had far-field charging for 12 hours a day, you’d need to deliver 1W to keep the battery charged. 8 hours? 1.5W. 6 hours? 2W and so forth.

With the right wireless power technology, that’s a real possibility. With the wrong wireless power technology, it’s not. If your wireless power technology maxes out at 10 or 50 or 100mW, you won’t be able to keep the phone charged. The charging rate would be less than the depletion rate and the battery would empty.

In short, choose wisely.

Thursday, May 17, 2018

Wireless power and the water tank

When people see our demos, one of the first questions they ask is: will it charge _____ ? (or can it power _____ ? )

The answer depends on the average and peak power consumption of the product in question, but we typically see three categories:

The first category includes products like a toy train or a speaker. The Wi-Charge receiver can consistently deliver enough power to operate the device.

The third category includes products like a Tesla electric vehicle. If the question is "Can you power a Tesla?", then the answer is "No".

The second category is the most interesting. These are products where their peak power consumption might be more than what a Wi-Charge receiver can deliver today. But, their average power consumption is less, and often much less, than what we can deliver.

For instance, a smart door lock may be idle most of the time but when a human approaches, that smart door lock might want to analyze fingerprints, or to recognize a face, or to upload access data to the cloud. That takes a lot of energy, but perhaps happens just few or just dozens of times a day. The peak power consumption is much higher than the idle power consumption.

Similarly, a security camera might have a proximity sensor that then senses an nearby moving object. That sensor triggers recording or analysis. But recording and analysis don't happen all the time - just several times each day

The solution there is to include a small rechargeable battery or other energy storage in the device. That battery can provide the peak power when needed, but charges when that peak power is not needed. It's almost like a water tank for a toilet. Water fills for a couple of minutes, but then provides a lot of water during a short time when flushing.

If the peak and idle power consumption is known and if the usage pattern is known, we can calculate what size energy storage is required. We can also determine how many such products can be powered at the same time from the same Wi-Charge transmitter.