Jump In When The Water Is Just Right With A Wireless Swimming Pool Thermometer

[David]’s family acquired a swimming pool. While it’s not his favorite activity in the world, every now and then he’ll indulge in the blue plastic bin full of water occupying previously pristine land in his backyard.

As he says, cool beer is pleasant, but cool water tends to put a damper on the experience. Rather than do something pedestrian like touch the water himself to discover its temperature; he saw an opportunity for a fun little project in a wireless temperature monitor.

The heart of the device is a Telecom Design TD1208 which runs on the French SigFox network. For a small fee any device on the network can send up to 140 12byte packets of data a day. Not a lot, but certainly acceptable for the Microchip MCP9700 temperature sensor it uses. He got the board up and running, and even made his own custom helical coil antenna.

The case was 3D printed out of PLA. It’s a tiered cylindrical bobber. The wider top section floats on the water and the base acts as a ballast, holding the battery and sensor.  The bobber is powered by a combination of  a questionable Chinese lithium battery, charging circuit, and solar panel. [Dave] was keen to point out that the battery is, technically, water cooled.

He wrapped up the code for the bobber and used SigFox’s SDK to build a nice web interface. Now, when the rare mood strikes him, he can remain inside if the conditions aren’t right for a swim.

21 thoughts on “Jump In When The Water Is Just Right With A Wireless Swimming Pool Thermometer

  1. paying some company to check how cold your pool is?
    the sigfox website makes me sick, completely impossible to navigate, subdomains everywhere, complete chance what links open in a new window and absolutely nowhere does it actually tell you anything useful e.g. how much a subscription costs. i suppose you throw the module away after a year and buy a new one?

    1. This guys website is themed around IOT fair enough but every project is based around SIFGOX?
      if you look up david tyr on linked in he workes for tmobile in CZ, nothing strange until ” – Internet of Things, Sigfox BO owner @T-Mobile”
      i don’t know what a “BO” is (body odour?) or why he owns one but this stinks! he is clearly paid by sigfox!

      1. Whoa whoa whoa…calm down. You know what you need? You need an IOT calming module with calming data gathering available from Sigfox for the low price of 47.95 plus monthly subscription.

      2. Zero, I had to google what the heck a sigfox was to write this article. I figured he worked for ’em, but he did write a nice article and I don’t see why you can’t just replace weird french chip with particle, esp8266, hacked up amazon dash, etc. This is hardly a promotion of the chip anyway. We don’t take money to write about stuff. Seriously. If I’ve ever promoted a product it’s just cause I liked it…. or I drank too much coffee and pulled a Voltaire, riding a caffeinated work psychosis to productivity town and getting articles out the other end. Since I’m a manically, almost militantly, positive person, most things I write probably sound too chipper for the average hackaday reader’s cynical and twisted pedant’s soul. Haha.

        1. @Gerrit : In this case, the “weird french chip” is a SiLabs Si446x radio + EFM32 ;)
          Sigfox is a network/service , not a chip maker

          Main difference with a Wifi-based solution (esp8266 or else) ? Simplicity.
          Sending data is a no brainer, you just have to focus on the sensor/application , not on configuring wifi access which is a pain. (+ huge difference on the battery life)

          _Disclaimer : Working for Sigfox myself._

      3. Haha, It is true that I am professionally connected to Sigfox (actually my company is) but also to NB-IoT and partly to LoRaWan. My blog is my own without any sponsors like you suggest believe or not :-) I personally like Sigfox because it’s so simplistic that even me is able to make a working thing LOL

  2. “Sigfox devices can work up to 20 years off two AA batteries, due to the fact it “wakes up whenever it sends a message, and then it goes back to sleep”, according to Thomas Nicholls, Executive Vice President of communications at the company.”
    *not sure what to say about that*

    Looks great, but a cell network based ‘IOTs’ device that tells you the temperature?
    I’m sure some would buy it, but not me.

    1. Now the quest for “an AA-size battery with a shelf life of 20 years or longer)” has started.
      Nice to know when your application can work for 20 years on 2 AA cells, but to make that claim true, doesn’t there has to be a battery that will be able to last for 20 years. As far as I know, most batteries expire a few years after production (that is unused in packaging, which is called shelf life).

      Please let me know when anyone finds one…

    2. A look at the datasheet says it burns max 3.5uA in sleep, that leaves plenty of room for some transmission, so 20 years is feasible in terms of battery capacity.
      My best guess is that for highly demanding applications, they will use special chemistry. For consumer stuff, good alkaline do 10 years shelf life, if the module is doing little enough work, discharging a small part of the battery, it will last that long. I don’t think a consumer will complain about getting to replace the battery in just 10 years.
      Now, let’s not forget that shelf life means the battery is still rather usable at that point, but your guess is as good as mine as to how much capacity should be left after the 10 years on a shelf: 90%? 50? 10? 0?

  3. I’m no battery expert but I think Lithium Thionyl Chloride batteries have such expected life (very low self discharge and therefore long shelf life if you don’t use them too). They do have very high capacity in AA. They do not like supplying lots of currrent and peak currrents damage their passivation in the long term (reducing their currrent output capability) but for low power IOT projects they are right. Look at LiMnO2 primary cells too which do not require specific decoupling like LiSoCl2 to address their inability to provide high currrent peaks.
    But I agree using Sigfox services for pool temperature monitoring seems like overkill and the low data rate it uses is meant I think to gain range, how many people have a property with a swimming pool 2km away from the house? All the more as I personnally would never give money for such a service.

  4. wiki says that (in mass) you can have IoT comms for a **YEAR** at $1 per device. I am jealous. Here we can but M2M GPRS cards and they cos $30 a month ($360 a YEAR) just to have the card!!!

      1. No, Pre-Paid is no different. In my country the telco’s only become competitive when external companies take a significant market share.

        As an example, I set up a sms gateway to send sms’s to my kids because I refused to spend the rest of my life carrying around something that is as delicate as a box of eggs. It would have cost 35c per sms to use providers in my country to I set up a server in the US that sent messages via the web to Canada where they entered the global roaming mobile network and they then went to my country which is in the southern hemisphere and that in total costed about 2c per sms.

        We need to set up a service to buy traffic allocations!!!

        Any takers?

  5. On the one hand, cool hack from a “for the hell of it” point of view. On the other hand, this has just taken something that should have no external dependencies, and made it rely on the cellular network, a third-party online service, and his house internet connection. Adding local connectivity to things is useful but gratuitously adding dependencies like this just makes all your stuff unreliable.

    1. Here in europe there are quite a few companies that are taking a swing at the LoRa thing. In a way, it is good because these devices are really handling over a lot of range and have great battery life compared to, say WiFi. From a consumer point of view, it’s much nicer to just get a device that works out of the box with a phone app and really setup nothing much. Of course, now they are not at a really good price point, but they will get there.
      The only thing that can beat them for now (excluding any system with dedicated gateway boxes) is whatever <1GHz wifi we'll get into the routers, but that is still much further away.

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