How to weigh your cat! – the IoT version

This is Leela. She is a 7 year old lilac white British short hair cat that lives with us. Leela had a sister who used to live with us as well but she developed a heart condition and passed away last year. Witnessing how quickly such conditions develop and evaluate we thought that we can do something to monitor Leelas health a bit to just have some sort of pre-alert if something is changing.

Kid in a Candystore

As this Internet of Things is becoming a real thing these days I found myself in a candy store when I’ve encountered that there are a couple of really really cheap options to get a small PCB with input/output connectors into my house WiFi network.

One of the main actors of this story is the so called ESP8266. A very small and affordable system-on-a-chip that allows you to run small code portions and connect itself to a wireless network. Even better it comes with several inputs that can be used to do all sorts of wonderful things.

And so it happened that we needed to know the weight of our cat. She seemed to get a bit chubby over time and having a point of reference weight would help to get her back in shape. If you every tried to weigh a cat you know that it’s much easier said than done.

The alternative was quickly brought up: Build a WiFi-connected scale to weigh her litter box every time she is using it. And since I’ve recently bought an evaluation ESP8266 I just had to figure out how to build a scale. Looking around the house I’ve found a broken human scale (electronics fried). Maybe it could be salvaged as a part donor?

A day later I’ve done all the reading on that there is a thing called “load-cell”. Those load cells can be bought in different shapes and sizes and – when connected to a small ADC they deliver – well – a weight value.

I cracked the human scale open and tried to see what was broken. It luckily turned out to have completely fried electronics but the load-cells where good to go.

Look at this load cell:


That brought down the part list of this project to:

  • an ESP8266 – an Adafruit Huzzah in my case
  • a HX711 ADC board to amplify and prepare the signal from the load-cells
  • a human scale with just enough space in the original case to fit the new electronics into and connect everything.

The HX711 board was the only thing I had to order hardware wise – delivered the next day and it was a matter of soldering things together and throwing in a small Arduino IDE sketch.

My soldering and wiring skills are really sub-par. But it worked from the get-go. I was able to set-up a small Arduino sketch and get measurements from the load-cells that seemed reasonable.

Now the hardware was all done – almost too easy. The software would be the important part now. In order to create something flexible I needed to make an important decision: How would the scale tell the world about it’s findings?


Two basic options: PULL or PUSH?

Pull would mean that the ESP8266 would offer a webservice or at least web-server that exposes the measurements in one way or the other. It would mean that a client needs to poll for a new number in regular intervals.

Push would mean that the ESP8266 would connect to a server somewhere and whenever there’s a meaningful measurement done it would send that out to the server. With this option there would be another decision of which technology to use to push the data out.

Now a bit of history: At that time I was just about to re-implement the whole house home automation system I was using for the last 6 years with some more modern/interoperable technologies. For that project I’ve made the decision to have all events (actors and sensors) as well as some additional information being channeled into MQTT topics.

Let’s refer to Wikipedia on this:

“MQTT1 (formerly MQ Telemetry Transport) is an ISO standard (ISO/IEC PRF 20922) publish-subscribe-based “lightweight” messaging protocol for use on top of the TCP/IP protocol. It is designed for connections with remote locations where a “small code footprint” is required or the network bandwidth is limited. The publish-subscribe messaging pattern requires a message broker. Thebroker is responsible for distributing messages to interested clients based on the topic of a message. Andy Stanford-Clark and Arlen Nipper of Cirrus Link Solutions authored the first version of the protocol in 1999.”

Something build for oil-pipelines can’t be wrong for your house – can it?

So MQTT uses the notation of a “topic” to sub-address different entities within it’s network. Think of a topic as just a simple address like “house/litterbox/weight”. And with that topic MQTT allows you to set a value as well.

The alternative to MQTT would have been things like WebSockets to push events out to clients. The decision for the home-automation was done towards MQTT and so far it seems to have been the right call. More and more products and projects available are also focussing on using MQTT as their main message transport.

For the home automation I had already set-up a demo MQTT broker in the house – and so naturally the first call for the litterbox project was to utilize that.

The folks of Adafruit provide the MQTT library with their hardware and within minutes the scale started to send it’s measurements into the “house/litterbox/weight” topic of the house MQTT broker.

Some tweaking and hacking later the litterbox was put together and the actual litterbox set on-top.

Since Adafruit offers platform to also send MQTT messages towards and create neat little dashboards I have set-up a little demo dashboard that shows a selection of data being pushed from the house MQTT broker to the MQTT broker.

These are the raw values which are sent into the weight topic:

You can access it here:

So the implementation done and used now is very simple. On start-up the ESP8622 initialises and resets the weight to 0. It’ll then do frequent weight measurements at the rate it’s configured in the source code. Those weight measurements are being monitored for certain criteria: If there’s a sudden increase it is assumed that “the cat entered the litterbox”. The weight is then monitored and averaged over time. When there’s a sudden drop of weight below a threshold that last “high” measurement is taken as the actual cat weight and sent out to a /weight topic on MQTT. The regular measurements are sent separately to also a configurable MQTT topic.

You can grab the very ugly source code of the Arduino sketch here: litterbox_sourcecode

And off course with a bit of logic this would be the calculated weight topic:

Of course it is not enough to just send data into MQTT topics and be done with it. Of course you want things like logging and data storage. Eventually we also wanted to get some sort of notification when states change or a measurement was taken.

MQTT, the cloud and self-hosted

Since MQTT is enabling a lot of scenarios to implement such actions I am going to touch just the two we are using for our house.

  1. We wanted to get a push notification to our phones whenever a weight measurement was taken – essentially whenever the cat has done something in the litterbox. The easiest solution: Set-Up a recipe on If This Than That (IFTTT) and use PushOver to send out push notifications to whatever device we want.
  2. To log and monitor in some sort of a dashboard the easiest solution seemed to be Adafruits offer. Of course hosted inside our house a combination of InfluxDB to store, Telegraf to gather and insert into InfluxDB and Chronograf to render nice graphs was the best choice.

Since most of the above can be done in the cloud (as of: outside the house with MQTT being the channel out) or inside the house with everything self-hosted. Some additional articles will cover these topics on this blog later.

There’s lots of opportunity to add more logic but as far as our experiments and requirements go we are happy with the results so far – we now regularly get a weight and the added information of how often the cat is using her litterbox. Especially for some medical conditions this is quite interesting and important information to have.

When your VU+ DUO just shows a red light and does not start up

So it happened to one of the VU+ Duos in the house. After a clean shutdown it did not boot up as expected but instead just showed the red light. It still blinked on remote keypresses and the harddisk spun up. Nothing else happened with it.

So it was bricked.

Reading the forums about that pointed to a capacitor on the board that quite regularly seems to fail. C807 is it’s name and it’s located near the Harddisk and the power-supply part of the VU+ Duo.

When I looked at the capacitor it did not seem to be faulty or anything. So without the right tools to measure I’ve decided to just give it a shot and replace the original 16V 220uF 85 degrees celsius capacitor with a 105 degrees celsius 16V 330uF one.

In my case I’ve taken out the board, to have a little bit of extra space, and cut of the old capacitor. Desoldering would be nicer looking but, well …

Replacing it on the left-over pins of the old capacitor was a matter of seconds.

After putting the board back in, the VU+ Duo powered up and booted as new. Brilliant!

working around MacOS X bugs: multiple “open with” context menu entries

Obviously it’s impossible for Apple to fix that quite annoying bug in their operating system that leads to double/tripple/… program entries in the “Open with…” menu. Everytime an application is updated it adds a new entry but does not remove the old one.

This makes your open-width menu look like this:

Bildschirmfoto 2013-05-12 um 18.11.38To fix this you need to run a simple command in your

/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user;killall Finder

This simple command will kill the double/tripple/… entries and restarts your to make the change visible. Your “Open with…” menu should now only show singular entries per application:

Bildschirmfoto 2013-05-12 um 18.14.11

gorgeous minecraft renderings – using opensource and blender

There you are – you’ve spent hundreds of hours, maybe together with friends, in a game called Minecraft. You mined and you crafted. And you built yourself your own world. Out of blocks.

“Minecraft is a game about breaking and placing blocks. At first, people built structures to protect against nocturnal monsters, but as the game grew players worked together to create wonderful, imaginative things.

It can also be about adventuring with friends or watching the sun rise over a blocky ocean. It’s pretty. Brave players battle terrible things in The Nether, which is more scary than pretty. You can also visit a land of mushrooms if it sounds more like your cup of tea.”

Those who haven’t played Minecraft yet – you’re missing out a lot. It’s fun and addictive. It seems pretty dull when you don’t know it. As soon as you got immersed in it you immediately see that it’s a lot bigger and the possibilities are a lot more varying than at first sight.

With all those blocks you can basically build your own world and humongously huge objects. It obviously takes a while in most cases because you (until you start using tools and mods) need to fit each block to the other in order to create those big objects.

So imagine you got your own world and you want to create nice renderings of it to hang on your real-world-appartment walls? You can use a very simple to use and thankfully free (open sourced) tool to do that.

It’s called McObj and it uses blender to render the exported geometry. Get it and send your renderings!

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a font for number people

OpenType is a font format which I personally might have underestimated in the past. Well you know – fonts and stuff. This all seemed not too interesting up until now. Now that changed dramatically when a font came to my attention which can be used for various purposes and as a font does not resemble the normal numbers and characters scheme. But what can it be used then if not to type numbers and characters?

Well. What about typing graphs?

Everything in the above image is generated by a font… like in your Word-processor (if it uses that font)

“Designed by Travis Kochel, FF Chartwell is a fantastic typeface for creating simple graphs. Driven by the frustration of creating graphs within design applications (primarily Adobe Creative Suite) and inspired by typefaces such as FF Beowolf and ­­FF PicLig, Travis saw an opportunity to take advantage of OpenType technology to simplify the process.

Using OpenType features, simple strings of numbers are automatically transformed into charts. The visualized data remains editable, allowing for hassle-free updates and styling.”

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a delicious raspberry pi

Just a couple of days ago – after a waiting time of more than half a year – my personal raspberry pi board arrived. Fantastic!

It’s small. Oh yes, it’s very very small.

What is the Raspberry Pi you may ask:

“The Raspberry Pi is a credit-card sized computer that plugs into your TV and a keyboard. It’s a capable little PC which can be used for many of the things that your desktop PC does, like spreadsheets, word-processing and games. It also plays high-definition video. We want to see it being used by kids all over the world to learn programming.”

For under 40 Euro you get a huge choice of I/O interfaces like USB, Ethernet, HDMI, Audio and Multi Purpose IO pins you can play with if you’re into hardware hacking. This small card is running a fully blown linux and because it has a dedicated graphics core which can hardware decode and encode 1080p h264 it’s definitely a good choice for a home mediacenter (yes, XBMC runs on it.)

It draws so little power that you could use solar panels to power it. It’s all open and sourced and I will use it for a couple of things in the household. Like a cheap Airplay node. Or a more intelligent sensor node for home automation. This thing seriously rocks – finally a device to play with – with reasonable horse-power.

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Mirror, Mirror on the wall

There are many things which are underestimated when team leads think about their team and possible actions to drive progress.

One of those things is that a team needs information to maintain and gain velocity. You cannot expect everyone to know just out of the blue what is important and in which direction everything is moving. To let everyone know and to develop that direction it’s important to share information as much as possible. It’s important to give everyone access to the information necessary to make a better job.

That’s why we had a build monitor at sones. We had a tool that displayed the current status of our build servers to all developers. Everytime someone committed a change, those build servers got this commit, built it and tested it with automated tests. The status of that could be seen by all developers as things happened.

So within seconds everyone could see if his commit did break something. Even better: Everyone could see. Everyone cared that the build needed to be working, that tests needed to pass. It was everyones job to do the housekeeping. When we switched from Team Foundation Server to GIT and Jenkins this status display needed to be replaced – you could immediately tell that things went from good to not-so-good in terms of build stability and automated testing.

Today I had the opportunity to take a tour of the Thomann logistics center. Standing in the support department I had this in front of me:

There were like 6 big status screens displaying incoming call status of the day, sales figures and other statistics important to those who work there. It’s a very important and integrated way to keep information flowing.

Since I am with Rakuten I thought about having a new status board set-up for my team. Something that might be inspired by the awesome status board which panic has built:

Since in addition to sones there are a lot of more things to track and handle (code, deployment, operations, overall numbers) I think such a status board will be of invaluable worth for the team.

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configuring the nano editor to my needs…

Configuring your favourite Editor on OSX (or Linux, or anywhere else) is important – since nano is my editor of choice I wanted to use it’s syntax highlighting capabilities. Easy as pie as it turned out:

I started with a .nanorc file from this guy and modified it to recognize some of my frequent file-types (like .cs files).

You can download my nanorc.tar – just extract it and put it into your user home directory.

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style your Visual Studio

It’s been some time since I’ve written about a Visual Studio Color Theme Generator. And obviously since then a lot happened in the world of customization tools.

The website is there to help the day with a lot of previewable Visual Studio styles. Even better: all styles can be exported for Visual Studio 2005, 2008 and 2010.


For Visual Studio 2010 you get a .vssettings file which can be imported into Visual Studio using the Tools->Import  and Export Settings… menu item.



For Visual Studio 2010 there are additional color styling options available. Microsoft offers a plugin for Visual Studio 2010 called Visual Studio Color Theme Editor. Using this tool everything else can be color customized. So you can have something like that:


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Source 3: Visual Studio Color Theme Editor

Want. To. Buy. :-)

Oh what a nice n3rd toy this would be. Rumors say it will be available soon for under $30. And for those who right now think: “What the hell is this?” – This is a coffee mug in the shape of a quite expensive canon lens. In fact I already heard of that idea more than a year ago and wrote about it here. At this time there were only hopes that it would be produced.