Recent Updates Toggle Comment Threads

  • Urban 15:41 on 11 Jul. 2015 Permalink  

    Torpedo marmorata 

    During vacation snorkeling I stumbled upon an electric ray. I was perplexed by its odd looks, and the fact that it seemed eerily undisturbed by my pursuit. Which is why I left it alone.

    Here’s a pic, and a short clip, taken with a modded GoPro Hero21.

    Marbled electric ray

    I had some trouble looking it up afterwards, but this nice guide helped me — it seems to be a marbled electric ray2. If I knew they were that common in Croatia, I wouldn’t have gone so close; supposedly they can produce a 200V discharge3, and on youtube you can find clips of fishermen getting shocked :)


    1. fitted with a mock underwater flat lens, made from a wide (Cedevita) bottle cap and a cheap kids’ diving mask; the aged Hero2, which I bought for the sole purpose of underwater photography, was completely unfit for it, despite having the housing rated for 200m–the original curved lens produced blurry images.

      Here’s a pic of the mod:



    2. also, Torpedo marmorata. It must be really common, since it has 8 names in Croatian: drhtulja šarulja, mramorna drhtulja, trn, trnjevača, tresnavka, banjača, pjegava drhtulja, renjok; see here []
    3. see here  []
  • Urban 20:50 on 31 Oct. 2014 Permalink  

    Smart thermostat shenanigans 

    Winter’s coming and this year I set my mind on installing a smart thermostat. I’m used to unexpected problems with tech, so I wanted to have it set up before it actually gets sufficiently cold outside that experimentation will cause me discomfort. Which means it’s now or never.

    I briefly looked into 3 options:

    • Nest, the epitome of a smart thermostat (acquired by Google)
    • Netatmo Thermostat, made by the French Netatmo, most known for its weather stations
    • Tado Smart Thermostat, made by Tado, a german HVAC startup
    • I also checked a bunch of other (locally controlled) options, of which nothing captured my attention

    To distill some of my findings (please note I’m doing this from an EU perspective):

    • Nest
      • [+] definitely tries to be smart; uses a motion sensor and a learning algorithm to find patterns in your away-from-home time
      • [+] the API looks pretty comprehensive & well done
      • [-] but it’s bulky and heavy
      • [-] and optimized for US heating standards & boiler interfaces (runs on 24V AC)
    • Tado
      • [+] supposed to work with most EU heaters
      • [+] the app reports distance from home to a server; when you get closet to home, it gradually increases the temperature (pretty clever)
      • [+] also supports plain old daily schedules for people without smartphones
      • [-] no activity detection
      • [-] no display or buttons, entirely app-controlled
      • [-] the most expensive of the bunch, but rental option available [+]1
      • [-] no API (none that I could find)
    • Netatmo
      • [+] supposed to work with most EU heaters
      • [+] relatively cheap
      • [+] nice design
      • [+] has an API
      • [-] the dumbest of the bunch (no sensors, no AI)
      • [-] just a web-based and app-basaed heating schedule editor

    I found out pretty quickly that Nest won’t cut it with my heating system. I don’t have 24V AC on my heater, and no AC power near my old thermostat mount location. In addition, the device itself felt pretty heavy/bulky. Last but not least, it’s Google-owned, so all the data about your physical presence and heating schedules will reside on the Google’s servers.

    So it was in fact a run-down between Tado and Netatmo.


    I liked Tado’s approach, but didn’t like the design of the device: no display, just a single “emergency” button to let it know that you’re home (e.g., if you happen to forget your phone at work). Monitoring the GPS position of all your family members to determine when to turn on heating is pretty clever and probably brings the largest possible amount of savings: even if you deviate from schedule, Tado still knows when you’re coming home.

    However, I can’t help but think about what can go wrong if you let your heating be controlled by a stack of unreliable technologies:

    • you have to have the phone on you (if you forget it at home, heating stays on; if you forget it at work, it stays off; nonetheless, that’s a pretty minor issue, since I rarely forget my phone)
    • but my phone battery dies relatively often; what then?
    • or what if you don’t have connectivity
    • or if the app’s GPS logging fails (i’ve experienced a lot of this with GPS logger apps, at least on iOS)

    On the plus side, Tado seemed to have some smarts regarding taking into account the outside temperatures, pattern detection (not much info online there), and it did specifically support my 3-pin (7-8-9) terminal of the Vaillant heater (which I saw in the installation video, no other documentation found).


    Netatmo looked quite nice, but the situation regarding available information online was even worse than with Tado. It seemed the dumbest of the three. The site shows nothing but HLB marketing, without any technical details. There’s no info about the features,  about what happens if you lose WiFi connectivity, or if it integrates with the Weather station. They do have a demo GUI that allowed me to play with a fake thermostat to get a feeling about what’s possible. I also had to dig deep to find it has an API that allows you to add some brains on top of it with your own app. And the fact that it took the original Netatmo Weather Station website quite some time to switch from HTTP to HTTPS was not really demonstrating the security savviness you’d like to see, if you want to let other people control your heating.

    However, in the end I did order this one–primarily based on the low price, appearance, and *claims* that it supports my heater brand (there was just a logo on the website). Not much info online here, just the video installation instructions that show it has a simple 2-terminal on-off switch, which I thought could be somehow connected to my Vaillant heater 7-8-9 terminal.

    Netatmo installation

    The first surprise was that I couldn’t get it to work in place of my old room thermostat. As it turns out, Vaillant 7-8-9 terminal is a potentiometer that gradually changes the voltage from about 11V (off) to 21V DC (full throttle) to regulate heating. This terminal cannot be easily linked to a single-pole switch. Arguably it could be connected to a 2 pole switch to have either off or full throttle.

    Luckily, the package comes with everything necessary for another mode of installation: It can be connected as a relay directly to the heater.

    In fact, the wifi relay comes with 2 backplates:

    • one is a socket plug, to connect it directly to mains. In this case, the “relay” acts only as a WiFi-to-radio relay and sends commands to the room thermostat module. In this case, the battery-powered room thermostat turns heating on and off.
    • the other one is a 4-wire connector that can be connected directly to the heater. Two wires (240v L+N, blue and brown) are connected to mains power (inside your heater), and the other 2 wires (black and grey) are connected to the relay connector of your heater.

    My heater (as probably every other Vaillant, I’ve checked a lot of online manuals) has a 240V relay connector on pins 3 and 4; they are normally bridged with a wire, which means that this 3-4 “switch” is always on, and heating is controlled through a room thermostat on 7-8-9. However, if you disconnect your room thermostat (i.e., all 7-8-9 wires are in the air, which means ON), the heating is controlled only through 3-4.

    Bottom line, I connected Netatmo relay adapter directly to the 3-4 terminal, and the power wires (240V) to L+N (both inside the heater). I also left my old room thermostat in place. This means both need to be active for the heating to turn on (logic AND). In my case this is easily solvable, because my old room thermostat can be set to “always on”, and this would mean the heating is controlled by Netatmo alone. But in addition, it gives me some peace of mind, because I can limit max temperature on the existing room thermostat as well, and prevent Netatmo from going berserk, turning on and heating the house to 30 degrees. (hey, it’s a cloud-driven thermostat, anything could happen)

    Post-install and first days

    I was pleasantly surprised by some of the features that are not mentioned anywhere on the web (in Netatmo’s defense, they do have a forum that I only found later:

    • It does work when WiFi’s down; it just follows the last schedule it knows
    • It does integrate with your weather station; it fetches the temperature from the outside module of the same account and uses it for plotting charts and doing predictive heating
    • It *can* have the polarity reversed, which means I could even connect it to the room thermostat post (off = all wires in air = full throttle; on = bridged control wire and low voltage)
    • It has 2 modes for heating: hysteresis and PID; PID means it learns the time constant of your home, takes into account the outside temperature and starts heating earlier or later accordingly

    Below are some screenshots from the web app Q&A that are not accessible from the demo web app linked above.

    2b6d6eda394b7aa134d663fc54e18d2c ce022b5f046edfa67dda51c5ed592af4b7a44523628e9746aca1a44de7eb9f16   6daef66bdeb8bb3fca9f6ead8bb9ec0d1e7d9f5de56e194e34f1985dfef560a5

    1. It seems Tado just dropped the price by 50 EUR []
    • Julia 13:21 on 8 Jan. 2016 Permalink

      has anyone had any trouble with it? Mine doesnt seem to want to control the temperature. my heating on my other box has to be on all the time, but even when my thermostat says its off, it still heats my home to somewhere between 20 and 25. I thought I had it working the other day but it seemed to turn the heating on when i set the desired temperature UNDER the current temp, and off when desired temp is over current….so far its costing me money not saving it!

    • Urban 15:13 on 8 Jan. 2016 Permalink

      From what you say, it seems that your heater uses reverse logic (meaning that you have to open the circuit to turn on the heating). Try changing the “polarity” under settings (in your app, go to settings -> your thermostat (at the top) -> Advanced settings (at the bottom) -> Polarity –> set to Reversed). If this is the problem, it should fix it.

    • Shambolic 12:06 on 11 Feb. 2016 Permalink

      I’m having a problem with the thermostat not turning the boiler on first thing in the morning. My current workaround is to have it switch on and off twice in the morning, trouble is sometimes it catches on the first one and therefore comes on a lot earlier than I would like. have it currently in the place of my old thermostat, with the relay just plugged into a mains socket. Maybe if it was hard wired into the boiler it would sort things?

    • Urban 23:26 on 11 Feb. 2016 Permalink

      Hmm, that’s hard to say.. I’m assuming the temperatures check out ok, with the thermostat actually measuring a lower temp than you’ve set? (If not, you can set the offset under advanced settings).
      Maybe there could also be a connectivity problem between the relay and the unit? To check this you can try changing the temperature in the app manually, and if that reliably works, this also can’t be the problem.
      Other than that, I imagine something like the heating prediction could mess things up (this tries to be smart and take into account the outside temperature, which could be wrong). You can try turning this off if you use it..
      Lastly, hard wiring it to the boiler might help, in case there’s some kind of hardware problem in the thermostat’s circuitry..

    • Shambolic 12:34 on 12 Feb. 2016 Permalink

      It’s a bit of a mystery. Temperature is fine, it works manually and after the first turn on the timed setting are working but it just misses that first timed switch on. I’ve switched off the predictive feature, no change. All that’s left to try is hard wiring to the boiler.

  • Urban 19:16 on 1 Oct. 2014 Permalink  

    If you want something new, you have to stop doing something old

    Peter Drucker
  • Urban 08:00 on 18 Jan. 2013 Permalink  

    Smart Watches, Dolphins and Evolution 

    Watches seem to be a bad fit in the modern world where time is all around us. Glance at your phone or your tablet, and there’s a clock. Glance at your computer screen, TV, car dashboard or digital camera, and there’s a clock. Fish your Fitbit out of your pocket, and it has a clock. Today, keeping time is so cheap that even your oven has its own clock.

    It wasn’t always so; 500 years ago, the clocks might have only been on clock towers. 250 years ago, they came to our living rooms. Then, to your grandfather’s pocket. And then, in an endless feat of miniaturization, they came to your wrist.

    However, in today’s world of Apple iPhones and Google Glass, the uni-tasking device on your wrist has been reduced to a fashion statement and/or a status symbol. But you don’t really need it.

    At least, I don’t.

    What would come in handy, though, is something else — an external screen for my phone. Something to display text messages, incoming calls, e-mails, weather info, and all the things the phone can think of, so that I don’t have to reach for it every time it blips.

    That’s why I’ve been testing a smart watch (Metawatch Strata, more below). It pairs to your phone using Bluetooth Low Energy and does all that, with hopefully more to come.


    A quick review

    Here’s some of the features:

    • It shows texts; see below for notification from one of my servers reporting some stats.1
    • Shows events from calendars synced to your iPhone; this includes Gmail, Exchange, and surprisingly, FB birthdays
    • Displays weather forecast, which is of course location-sensitive; the phone already knows your location, so weather can always be local
    • Shows stocks and phone battery level
    • Displays incoming calls, which you can also reject by pushing a button
    • Has media player controls,
    • Features a vibrating motor to alert you to a call, text or a calendar event,
    • as well as a 3 axis accelerometer and an ambient light sensor, both unused in the current firmware.



    All this works by pairing the watch to your iPhone (Android is supported, but currently lacks many features). In fact, you have to pair it as a Bluetooth 2.1 device for displaying texts and incoming calls (as you would your Bluetooth car kit), and as a Bluetooth 4.0 device for everything else.

    Once paired, you run the app (MetaWatch Manager) that manages the widgets on the watch. You get 4 screens and you can place on them anything from 4 small widgets to 1 large widget occupying the entire 2×2 grid.


    The software is supposed to be open source, and there’s plenty of projects doing more with it. Haven’t looked into it yet.

    One of the more peculiar things is its display, which is nothing I’ve ever seen before. It’s a Sharp low-power memory LCD (video) with 96×96 pixel resolution, but there’s no black or white pixels; the only two states are mirror-reflective and white. This takes some getting used to, so be sure to check if you like it before buying. All photos are cleverly set up to reflect only black, so the effect is not obvious unless you check it in a video. On the bright side, it requires almost no energy when it’s not updating (similarly as e-ink), so the battery lasts for about a week.


    So, is this wearable computing?

    MetaWatch is of course not alone; there’s Pebble, which is just about to ship, with similar features. Pebble uses an e-ink display, so the battery life is reportedly similar (around a week). There’s also the Italian i’m Watch, which is entirely Android powered and uses an active display (hence the battery only lasts for about a day).

    It’s quite obvious something is going on in that space, and that a new computing form-factor is emerging.

    And if you think back, the exact same thing has already happened before: computers started out as large mainframes, where all the computing power was centralized. They were accessed only by a dumb terminal, which was little more than a remote keyboard and screen. Yet, gradually, technological progress killed the mainframe and made the dumb terminal the new protagonist. It became smart enough to survive by itself, sitting under your desk, then on your lap, and finally in your pocket. The smart phone in your pocket is indeed more powerful than your desktop computer was 10 years ago.

    And yet again, there are new dumb terminals to take place of the old. Smart watch is nothing but a dumb terminal for the mainframe in your pocket. Right now it can’t do much more than display what the mainframe has to say. But it might not be long before you won’t need the mainframe anymore.


    The meandering path of evolution

    I’ve been thinking lately how all this relates to biology. Watches seem to have had a similar evolutionary path as dolphins.

    You see, first there were fish (bear with me). Gradually, some fish got tired of water, became mammals, grew lungs and legs and came to land. They evolved further, and eventually they became us. But something else also happened: a group of mammals got tired of land and went back to water. Dolphins are a part of that group, and so are whales. They might swim like fish, but they have lungs and have to come to the surface for air. And funnily, today they mostly hang out with other fish (which have always been fish) and get confused with them by almost everybody.

    Compare that to watches. A clock, as an ideal of craftsmanship, the ultimate precision mechanism, gradually evolves into a mechanical Babbage machine that fills an entire room. Later, that becomes a computer, and the computer gets smaller and smaller, until it becomes wearable, and finally migrates to your wrist. There, it hangs out with the old mechanical relics, only to be confused with them for years to come.



    1. I’m using Nexmo to deliver those, costing me 1 cent per message []
  • Urban 02:35 on 1 Dec. 2012 Permalink  

    625 days of walking 

    I’ve had my Fitbit for over 625 days. It records walking activity with 5 minute resolution and I’ve carried it around almost everywhere.

    So here’s my past 1.7 years of walking in one picture (click to enlarge).

    Every column represents five minutes (288 columns from 00:00 to 24:00) and every line represents a single day (625 lines from March 15 2011 to November 28 2012).

    Green means no activity and red means high activity (highest intensity red is 706 steps in a 5 minute interval).

    What’s immediately visible is when I wind down and go to bed. Then there’s some displacements where I was obviously traveling in a different time zone.

    There’s also a trend that I’m not fond of: I seem to be rising earlier and earlier, since the active (yellow/red) band is moving slightly to the left as time progresses.

    A quick note on how this was compiled: the data was extracted from the Fitbit website, using the undocumented API that fuels the flash charts (the cookie that serves as auth was copied from the browser’s inspector into the script). I looped through the entire date range and saved every day into a separate XML file. Another quick and dirty script combed through the files with a regex and concatenated all 5-minute intervals in a day into a single comma separated line. The resulting CSV file was then imported into Excel where simple normalization was done, as well as some color coding using conditional formatting. Yes, this is extremely lame, but it was all finished before I could even decide what other tool to use.



Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc