SKT Smart Home: making of a motion sensor

Small lifting electromagnet

SK Telecom's Smart Home device line-up was conspicuously missing a motion sensor. It would have nicely complemented the Jikimi home security devices. Considering that the PIR (passive infrared) sensor itself doesn't cost all that much (some as low as US$2) or complicated to work with, it wouldn't have been so hard to create a product out of it.

It turned out that SKT wanted that as a part of a much more beefed up home security solution called "T View Sense" that came out last month. It's a cloud-connected IP camera with the optional sensor package (motion, door, temperature/humidity, smoke, and carbon monoxide). The sensors requires the IP camera to function because they communicate to the server via the camera's integrated gateway. I appreciate the effort SKT is finally making to counter the IP camera efforts from the other mobile carriers (LGU+ had theirs since 2013), but the pricy nature of the camera (official price of KRW159,000 or about US$140) is off-putting to someone who's just interested the sensor alone.

So I decided to be a bit creative and repurpose one of the existing Jikimi devices into a motion sensor instead. Initially, I wanted to modify the SOS button because it was cheaper. But the fact that the alarm it makes doesn't get differentiated between the buttons made it a deal-breaker. With the door sensor, I needed to simulate the door closing/opening with a magnet, meaning that I could either attach the included magnet to a motor or use an electromagnet to fake such action.

Getting the door sensor to sense the electromagnet

Obviously, I chose the electromagnet because it would be far more simpler if it worked. If it generated enough magnetic field, it would act like the original magnet and cause the sensor to send a "door closed" signal. The problem was that I wasn't sure what kind or how big of an electromagnet would be necessary. After looking at various offerings on the internet, I decided to take a stab in the dark and buy a small "lifting electromagnet" used in machines for picking up metallic items. The particular model I bought for about US$5 was rated for 2.5kg at 12V DC, consuming 3W. The model number KK-P20/15 apparently indicates a 20mm outer diameter and 15mm thickness.

12V was tad higher than what I wanted, but the electromagnet works at a lower voltage with reduced pulling power. All I needed to know was whether that pull is just enough to trick the sensor, so I created a quick testing platform with my kids' electric circuit kit. As you can see here, 3V was just barely good enough for the sensor to activate. At 6V, it worked more reliably. This confirmed two things - the electromagnet I had was fit for the job and that I could make it work with a battery pack, e.g. single-cell Li-Ion battery (3.7V nominal).
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Disable camera shutter sound on iOS 10.0.1

Select AssistiveTouch as Accessibility Shortcut (left), then leave "Mute" as its only top level menu (right)

iPhones and iPads bought (or intended to be sold) in either Korea or Japan has the camera shutter sound forcibly turned on at maximum volume no matter what sound setting is used. I've noted this three years ago. This is due to local regulations, but even making a screenshot causes the same sound, which is inconvenient.

Recently, though, someone at Ruliweb has posted an interesting tip that can override this if you're using iOS 10.0.1. I would like to share this information here.

1. Run Settings app and go to General > Accessibility

2. Scroll to the bottom and enter "Accessibility Shortcut" option. Select "AssistiveTouch".

3. Back in the Accessibility menu, scroll up to the middle. Find and enter "AssistiveTouch" option.

4. Enter "Customize Top Level Menu" and remove icons until there's only one left. Select "Mute" for this icon. (If you leave two or more icons, this tip will not work.)

When you triple-click the home button, a small floating AssistiveTouch button will appear on the screen. When you press it, the system sound will be muted completely, including the camera shutter sound and alarm. Pressing the AssistiveTouch button again will re-enable the system sound, and triple-clicking the home button will hide the AssistiveTouch button.

In a nutshell, you can use AssistiveTouch to disable or enable camera shutter sound at will. User reports indicate that the tip works across all devices, including iPhone 7 that I personally confirmed. However, it doesn't seem to work on iOS 9. Therefore it isn't clear if this is a bug or an intended effect. Use at your discretion.
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The only thing that I carry is everything

Wearing my all-inclusive belt bag on my waist

Nearly a decade ago, you would have seen me wearing all sorts of gadgets around my waist, as evidenced by this television broadcast. The problem with this was clearly illustrated in that video - it takes a bit of time to put them all on the belt, however useful they may be.

I haven't let go of the carry-them-all attitude, but things have worked in my favour. A lot of the gadgets I had to carry separately were now integrated into a single device (smartphone). That meant less stuff to carry, and I was able to reduce the number of pouches and bags on the belt over the years. I ended up with a phone and an external battery each in a holster, and a bag that held adapters, cables, and other miscellany.

iPhone 6S Plus and external battery are easily accessible

But then large iPhones came along. When I put it on my belt, it occupied a sizable area of my waist. This got me thinking: since the phone is thin enough, maybe I could put it in a belt bag that can store other stuff with it. And this is how I now just have this one bag hanging from my waist.

As you can see here, my iPhone 6S Plus and the slim external battery fit nicely into the front pockets of the bag. They're accessible by opening up the flap usually held in place with a hook-and-loop fastener. I also have a paper clip there in case I need to change the SIM card or poke a reset button.

Of course, there's a lot more hiding behind. Let's take a look at the rear compartment.
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FLIR One 1st gen on iPhone 6S Plus

Opening the packaging of the first generation FLIR One

A few months ago, I noticed that the first generation FLIR One thermal imaging module for iPhone 5 & 5S went on a bargain sale online for about US$110. Since the newer version and the competing products were two to three times more expensive I thought it would be a great chance to own a thermal imaging camera of my own and ordered one. Good thing I did, because as of this writing the price went back up so high that you'd be better off getting the newer version.

Mine arrived after a couple of weeks and I was already impressed with the nifty packaging. The product itself was also well-built and tightly integrated with my iPhone 5 once I put it into the provided case. Functionally, it works pretty much as advertised. You can see the thermal images of your environment through the phone's screen, with objects' contours enhanced using the images from a regular camera next to the thermal one. This technique, called MSX, is a way of mitigating a relatively low pixel count of the sensor (80 x 60 = 4,800). You have to recalibrate the sensor from time to time using a sliding switch next to it, which is slightly inconvenient at times.

FLIR One works fine with iPhone 5, as intended

Other device specifications limit the use of this module mostly to indoor use. The maximum range is about 30m (100 feet) and can only detect between 0ยฐC to 100ยฐC (32ยฐF - 212ยฐF). It does work quite well if you work within these limits, though. I can see where the heat leaks in my house and whether the floor heating is working properly, to give some examples.

To me, the fact that it works only with iPhone 5 or 5S out of the box was its biggest disadvantage because the larger iPhone 6 and 6 Plus series came out just two months after its official availability. FLIR did address this problem by releasing a second generation model a year later that solved the form factor problem (just plugs into the bottom of a phone) along with an upgraded pixel count (160 x 120 = 19,200) and range (-20ยฐC to 120ยฐC). It also does auto-calibration, boosting its convenience. But what about for those who already own one and upgraded to the newer iPhones?

You could use it on a spare iPhone, like I initially did, or modify it. There are aftermarket phone cases to fit an iPhone 6(S) or 6(S) Plus. But these require you to cut off the curved area to the side of the connector on the module so that they won't interfere with the wider width of these phones. Otherwise, the Lightning connector wouldn't go all the way in. But I did not like to mutilate it like this and decided to find another way.
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A quirk with SKT VoLTE on iPhone 6 Plus

For the past two weeks, I've been having a strange problem when attempting to place calls with my iPhone 6 Plus. Many of the phone numbers that I know for sure exist would be met with "the number you dialed is not in service". If I switch the "Enable LTE" option in Settings app to "Data Only" instead of "Voice & Data", the phone calls would go through just fine. So it had to be an issue with VoLTE.

I first contacted my carrier, SK Telecom, to see if this was a problem at its end. But nothing turned up and I was eventually advised to contact Apple instead. Sure enough, colleagues using iPhone 6 on the same carrier did not have the problem. Digging deeper, I discovered that the problem did not occur only if I had country code prefix (e.g. +82 for Korea) on the phone number. So while +82-10-xxxx-yyyy would work, 010-xxxx-yyyy wouldn't.

Seeing that it might be some sort of a weird software issue, I contacted Apple support about this. Unfortunately, no clear solution came up, either. As a last resort, I was told to do a complete factory reset and see if that helped. As the troubleshooting was reaching a dead-end, I got a carrier settings update as I opened up the "About" page in Settings app. It updated the carrier settings from SK Telecom 18.x to 19.1. I told the support that I'd see if this update did anything, and if not, I might try the factory reset.

I attempted several calls to various places with the VoLTE setting on, and I saw that all of the calls now made through regardless of the country code prefix. The update apparently fixed the problem. It was indeed a software problem, but it was somewhat caused and fixed by the carrier. I reported this success to Apple support.
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Copyright (C) 1996-2016 Wesley Woo-Duk Hwang-Chung. All rights reserved.