Mark Asbach - All Articles

WordPress, Django, Indieweb, and the Homebrew Website Club

2025-06-17T21:07:49Z

This blog has been up for quite a while now. It still looks clean and minimalist to me, but it definitely isn't sleek at all. That's okay, I'm not an artist and this is a personal blog. I don't have to sell anything or pretend.

A few months ago, one of my bands decided that we need a new website, though. We have been happy with Facebook to promote upcoming gigs and document them afterwards with a few images and sometimes a short video. But public Facebook profiles are getting more and more locked down by Meta, so that they are effectively useless if you don't want to log in.

This is why we want to own our content and publish it ourselves. So I set up a WordPress site - because that's what everyone does and there's tons of themes. But I had just one little wish: I wanted two independent streams of blog posts, each with their own RSS feed. One for the upcoming events and one for our actual blog content. And after one day of fiddling around, I finally gave up and started a Django application from scratch. To my surprise, I had an initial version ready after just a few hours. It's live now at https://pimentamalagueta.de.

The funny thing is: I had the impression that I'm a novice at building a homebrew website and I'd really like to meet up with others to exchange ideas and learn. And just a few days later, I stumbled upon Jochen's Weeknotes where he wrote about the formation of the Homebrew Website Club in Düsseldorf.

Today, I've attended - and I'm really deligted. I didn't even get that Indieweb is not just a website, but a real movement with plenty of people, ideas, and documented knowledge, best practices and tutorials. I've already refined the rel-me links for RelMeAuth on this blog and added h-card markup to my profile today. Cool stuff!

Next thing up will be h-entry markup for my blog articles and hopefully Webmentions.

Playing Roborally with your friends over the internet

2026-08-19T15:55:43Z

Yesterday, I've revived my blog, because I had revived one of the projects that I originally wanted to share when I launched this blog seven years ago.

But this hasn't been the only project that I wanted to open source but never found the time to clean it up at least so far that it can be useful for others. I'm currently at the Chaos Communication Congress and the projects around me have been motivating to invest a few hours to clean up my own projects, too.

So, here's the next one, that I'd like to share - at least for a couple of friends who like to play Roborally:

https://bitbucket.org/markasbach/corobot/

It's a very simplistic approach to make Roborally playable remotely via videochat plus a web application. It requires to use the physical tabletop game and players need to enter results of everything that happens on the board (no game mechanics are implemented). But I actually prefer technology to not solve things that humans can do best, but assist in the things that are labour-intensive - or in this case impossible: sharing a deck of playing cards with remote players.

Seven years later

2026-08-19T15:56:03Z

It's been seven years that this blog exists - but it just sat there while I was busy. A relationship broke, others came and went, some came back ... but the Arduino fix for the fridge still works at my wife's place. That's been much more sustainable than expected!

As I'm heading off to my first Chaos Communication Congress, I've spent some hours to finally open source some old projects. This includes the fridge project and I'm sharing it now on https://bitbucket.org/markasbach/fridgeduino/.

Originally, I planned to prototype using the Arduino UNO and then build a minimal version using an ATtiny. Also, I thought about adding a second temperature sensor, a door open sensor, and a way to control the temperature without having to reprogram the micro controller. However, I found that all these things weren't really needed. My wife recently reprogrammed the temperature window to be 0.5 degrees warmer - and that's all that had to be changed during the 9 years that this fix is in operation (plus replacing the first relay after 1.5 years, of course).

For reference, these were some previously researched existing pieces of information that helped to get this done:

Low Power Arduino:

Temperature sensors:

Carbon footprint and veganism

2017-04-12T19:04:01Z

A while ago, a friend posted a video from Spiegel Online, in which the author claims that 18% of global greenhouse gas emissions were due to meat production, which would be more than the amount produced by transportation. He literally claims that "someone who eats less meat helps the planet more than someone who leaves out the next plane trip".

My friend also posted a graphic (Cowspiracy) that claims that "a plant-based diet cuts your carbon footprint by 50%" and that 51% of global greenhouse gas emissions are "due to livestock and their byproducts".

Since I'm concerned with a sustainable lifestyle, but also love to eat meat and drink milk, I asked myself, if these numbers could be right and if I could and should change my eating habits. Based on a great TED talk that introduced the idea of the "weekday vegetarian", I have reduced my meat consumption years ago. A rough estimation lets me assume that I consume about 500 to 800 grams of meat (including fish) per week, so I start from a medium level already.

TL;DR

Spiegel Online gives numbers that a higher than the data I could find, but still in a credible range. The comparison to transportation is wrong, though.
The Cowspiracy poster is total nonsense. Probably, statistical data from other sources has been mixed up here, as a plant-based diet roughly cuts your carbon footprint for food to 50%, but this makes only about 7 to 10% of your total carbon footprint.
What really surprised me was, that "other consumption" is actually the biggest fraction of a German personal carbon footprint. It seems to be much easier to reduce your personal emissions, by buying less stuff like clothes, electronics, furniture, etc. than by optimizations in the fields of food, energy, or transportation.

Data from Umwelt-Bundesamt

The first source of information that I checked was the carbon footprint calculator of the German federal office for ecology (Umwelt-Bundesamt). It walks you through several aspects of your life that result in carbon emissions. Based on their data, the average German produces about 11 tons of carbon dioxide per year - and my personal footprint is about 7 tons. Food actually accounts for 1.75 tons for an average person and 1.05 tons for a vegan. So 0.7 tons per capita can be accounted to meat production, which is less then 10%. So, at least for Germany, meat production accounts for a lot less than 18% of our greenhouse emissions, as far as the Umwelt-Bundesamt goes.

Compared with 1 hour of domestic flight (0.17 tons CO2) or 1 hour of intercontinental flight (0.24 tons), leaving out the next flight will definitely have a higher impact than eating less meat. Coincidentally, my friend who posted this video on Facebook is currently travelling Asia. According to the Umwelt-Bundesamt, a oneway flight from Cologne to Bangkok produces 2.78 tons of CO2 per person, equivalent to four average Germans that would go totally vegan.

Now, it usually makes sense to double-check data with different sources. So, I first checked the general data on greenhouse gas emissions from the Umwelt-Bundesamt. There, I find data that accounts 7% of all greenhouse gas emissions in Germany to agriculture, which is even less than my calculation above.

Data from Bayrische Landesanstalt fuer Landwirtschaft

The problem here is how to count greenhouse gas emissions. Typically, laughing gas (N2O) and methane (CH4) are expressed in CO2 equivalents and summed up and both gases have a much higher impact per molecule than CO2, so slight differences in the N2O or CH4 calculations can have a high impact and these are specifically found in agriculture, adding up to about 60% of the carbon equivalent greenhouse emissions of agriculture according to the Bavarian ministry for agriculture (LWL). A paper found on their website assumes that 13% of all greenhouse gas emissions in Germany are produced by agriculture. This is twice as much as the data from Umwelt-Bundesamt, but still much less than the numbers claimed by the Spiegel Online or the Cowspiracy poster. Furthermore, the paper states that, including animal feed, livestock accounts for two thirds of the carbon equivalent produced by agriculture. This is again a deviation from the Umwelt-Bundesamt data where meat consumption makes up less than 50% of a personal carbon footprint, but still in the same order.

Data from World Wildlife Foundation (WWF)

Since one could argue that German public institutions might be politically influenced, I also consulted the data provided by the World Wildlife Foundation that runs a campaign for eating less meat. Their website actually carries a lot of information and very detailed and well researched papers with lots of literature references and meta-studies. So, if you are interested in details and in a neutral source, visit their website on meat consumption. The data found in the relevant PDF is more or less the data used by the German ministries. Instead of "two thirds", the WWF writes that meat accounts for "nearly 70%" of the greenhouse emissions of agriculture, though, which sounds like more :-)

How to improve

The big question is now: what should I do to improve my carbon footprint? The calculator from the Umwelt-Bundesamt was very enlightening here. It splits the your carbon emissions up into these categories (numbers in parentheses are German averages):

Heating (1.75 tons)
Electricity (0.79 tons)
Mobility (2.19 tons)
Food (1.75 tons)
Other consumption (4.42 tons)
Public emissions (0.73 tons)

Instead of concentrating on things like a new fridge or vegetarianism as most important, it is clearly the "other consumption" category that is easiest to influence. As I really do not spend much on consumption (my bike is 20 years old, I don't have a car, my furniture is old, I just repaired some pairs of jeans ;-)), my personal footprint is already much lower than average. Also, I live in a very modern house, reducing my expenditure on heating a lot and I don't have a car, so my numbers for mobility are also lower than average. This year, though, I just travelled to Cyprus, which makes a huge difference to the last years where we mainly travelled by train and bike through Germany.

So, what I'll keep in mind is to not travel too much / too far and to keep consuming less. I'm happy with my rate of meat consumption, though ;-)

Fixing a fridge WITHOUT using an Arduino :-)

2017-02-01T22:51:50Z

If your fridge breaks, chances are that you don't have an Arduino, a Dallas temperature sensor, and relays lying around. At least I didn't when mine broke and unfortunately, it was a very hot summer day when it did. So, here's the most simple fix:

Use a timer switch.

Many people might have one already to switch on Christmas lighting in the afternoon and switch it off in the mornings. These timers work quite well to control your fridge as well. As explained in the blog post on using an Arduino to control your fridge, the basic operation of a fridge is to switch on cooling for half an hour or so and then switch it off for the next hour. The proportion of "on" time versus "off" time gives to the actual cooling rate. It turns out that once you found out a good proportion, you won't have to adjust it for weeks, unless the weather really changes (i.e., temperatures drop or rise a lot).

At first, I thought, a digital timer would be great, because I found a cheap model that let me set up to 20 on/off per day exact to the minute. However, it showed that this fine granularity is not needed. Instead, a analogue timer is much easier to adjust, although it might only allow to set on/off for 20 minutes slots.

There are only few things to take care off:

Once you switched the fridge off, always keep it off for more than 15 minutes. This is to let the pressures readjust so that the compressor can start more easily. In case you switch the compressor on after a too short period, it might not be able to start and block (and in worst case get damaged). So, make off time slots longer than 15 minutes - always.
Once you switched the fridge on, let it run for more than 10 minutes. The first minutes will not show any cooling effect at all, as the compressor first needs to build up pressure. So, make on time slots longer than 10 minutes ;-)
The physical system has a large time delay: First, the compressor needs to work some time until the cooling parts inside the fridge really get cool. Then, slowly, air will cool down and convection starts, letting the cold air sink to the bottom of the fridge and bringing warmer air up to the cooling elements. But it will take even more time for the cold air to cool the actual food that you stored in your fridge, in turn heating up the air again, making it travel upwards to the cooling elements and so on. As a result, you will notice, that after you start the compressor, it will take about 10 to 15 minutes where the fridge only gets warmer, until finally, your temperature sensor 'sees' that there is any effect. After a couple of minutes, the decrease in temperature will reach a steady rate. Then, after you stopped the compressor, temperatures will keep decreasing for a further 10 minutes or so, as the convection process is still functional as long as the cooling parts are cooler than the air inside the fridge.
Similar physics apply when you open and close the fridge door: This will rapidly increase the temperature inside because you swap cold air with warm air. However, even if the compressor is not switched on, convection and heat dissipation from air to stored (cold) food will let the temperature gradually fall again. Of course, storing warm food will do the opposite: it will let the temperature rise slowly, because the air heats up.

Sounds complicated but in practice it's pretty simple. First, put on the compressor constantly, until your (recently broken) fridge reaches the target temperature. Then install the timer and set it to 50 % on 50 % off. This could be one hour on, one hour off, one hour on, ..., and see where this gets you. We found that waiting for half a day gives you some idea on which direction you should take: more cooling or less. After three days, we had a fridge that worked pretty well, while I was waiting for the Arduino to arrive :-)

Fixing a fridge using an Arduino microcontroller

2024-12-28T19:56:54Z

Our fridge broke during the summer of 2015, more or less on the hottest day. It had only been five years old and we had bought it to be eco-friendly but affordable, so it has an A+ rating (in 2010's standards, more on this below).

It turns out that a typical cause for this is a broken thermostat and in fact it was in our case. The replacement thermostat is a 30 EUR to 40 EUR mechanical part that can be easily found on eBay. It looks like this: https://ebay.de/itm/171288968757. Unfortunately, in our fridge, the capillary (the metal wire) is installed behind the insulation. To replace the part, one would have to disassemble the whole fridge, dismantling it first. Commercially, it makes no sense to have it repaired by a technician as this would be far too expensive.

But we didn't want to throw out the whole fridge just because of a single broken part. So I figured, it would be the ideal reason to start tinkering with an Arduino microcontroller. After some planning, I bought parts that cost about 40 EUR in total, the most expensive part being the Arduino itself, costing 20 EUR. A fully calibrated digital temperature sensor is about 1 EUR to 2 EUR, a mechanical relays fitted for Arduino is 5 EUR to 10 EUR, and you will need at least a pull-up resistor and some wires (< 1 EUR). There is a lot of source code out there already and documentation on temperature control projects. The actual work was about one day, including understanding Arduino, but of course since this is fun, I started tweaking and optimizing it. I've put some documentation online on the Arduino Playground Wiki. It needs some updates, plus I will put the source code online somewhere in the next days.

I had fixed it in 2015 originally, but now it runs for more than a year. After a couple of months, the original relays broke, so I had to solder in a new one, and doing this, I moved the relays into the housing of the original thermostat, so it looks a little more tidy.

Regarding the ecology, I am not sure if the fridge is really energy saving one, now that it is nearly seven years old. It may have never been as eco-friendly as stated by the manufacturer, which you can see from the following calculation:

The model is a Bauknecht KGA 325 Pure/1 Optima WS and it is supposed to consume 0.74 kWh per 24 hours or 270 kWh per year, which gave it its A+ rating. The rating plate lists 0.7 A at 250 V, which lets me assume that the compressor actually would consume 4.2 kWh a day, if run continuously. In other words: the manufacturer assumes that the compressor is on about 16 percent of the time. During summer, it seems to run more like 60 % to 80 % of the time, now in winter, I'd say it's 40 % to 50 %. The room it is standing in is heated to 19.5 C and I've programmed it to keep about 8 C at the thermostat. This seems to be a rather typical setting, so unless I'm missing something here, the energy rating itself is far from reality.

Brexit

2017-01-29T14:30:47Z

Should a personal blog start with politics? Maybe :-) The last year has been very turbulent regarding international politics. Be it Middle East wars, US elections, or the demise of democracy in Poland - it's been bad news all around, most of which was unexpected, at least to me.

The only thing that could have been anticipated, though, was the Brexit.

To be honest, I really didn't think this would happen. But in fact, during spring, I jokingly told several friends, that a Brexit vote might be "funny and good for Europe."

Everyone seems to complain about European bureaucracy, where in fact it makes a lot of things easier: No pressing need to research trustworthy product quality labels as a comparably high standard is already defined by EU law. Compare prices across countries when doing online shopping: because of standards for how to display taxes and because of minimum standards for customer protection, it's easy to do. Many countries even have the Euro that makes EU-international shopping easy (this one does not apply to the British though, as they have never experienced the full benefits but shared a lot of the undesired consequences).

But as long as no country ever left the EU, no-one would personally experience the actual benefits of being a long-time part of the union. I imagined that a Brexit would make the perfect example.

Travelling Europe, I've learned to love people and places and wherever I went, I found things that where better than at home, new ideas I could learn from, interesting view points that I didn't see before. I can say that I really like globalization for these insights. And Britain is a good example for this: politeness, openminded and friendly people, humour, and a lack of Besserwisserei is what I found. If we could make Europe a little more British in this regard, it would be beneficial to all. Now, especially as I expect a drastically negative outcome, how could I wish - even jokingly - that a Brexit ever happened? The simple answer is that I don't think there are many economies that would survive exiting the EU, but the UK would. Also, since the British have always appeared pragmatic and rational to me, I would expect a clear change of the public opinion and thus an early correction of the political path, independent of the political party in charge at the time.

Until now, everything is theory, but the dice have been thrown. If all goes well, we will see enough impact on UK economic factors before any Brexit plans have really been put into operation to turn the sentiment. Ideally, we would even see a broad movement towards a real European Union, with enough momentum to correct its (undisputedly existing) flaws together.

New Year resolutions

2025-06-17T21:04:58Z

It might look like a New Year resolution, that I finally started this blog. However, it's merely a coincidence: over Christmas, I've found time to get some projects done (like fixing the fridge using an Arduino - more on that later), which now makes this blog the next entry on my to do list.

So, Happy New Year, little blog, let's get started :-)