Java on ads' corner

Hamburg PostgreSQL Meetup in April 2024

Mon, 29 Apr 2024 00:08:58 +0200

On April 23rd - after a very long break - the third PostgreSQL Meetup took place in Hamburg.

Sascha had temporarily taken over the Meetup group after the previous admins were no longer available. Last year at PGConf.DE 2023 I asked if there is anyone interested who would like to revive the group. Tobias had agreed to do so, and Lenz also joined the effort at the PGConf.EU 2023. After a few organizational details, the first (or rather third) meetup was scheduled.

Does an openHAB Item exist?

Sat, 19 Mar 2022 23:14:00 +0100

In a more complex openHAB2 Rule I’m writing, I need to find out if a certain Item exist. If I try to access it when it does not exist, the Rule will fail. Not good.

I could pass in a parameter to the framework which builds the Rule, but that is cumbersome and requires changes on several places.

Let’s see if I can have the Rule figure this out.

openHAB: stop a ChromeCast

Wed, 10 Feb 2021 20:09:00 +0100

There are a number of ChromeCasts in our setup. I’m adding (physical) switches to turn displays on and off, and primarily control the volume. When I turn the display off, I also want the ChromeCast to stop doing whatever it is doing right now (stop streaming), and go back to the default application (for video CC).

openHAB: timestamp from last Item update

Thu, 28 Jan 2021 20:25:00 +0100

If openHAB has a Persistence service configured, the time of the last Item update (and a couple other times) is available in Rules. This makes it quite handy to check if a certain item hasn’t been updated in a long time. As example I have the Tankerkoenig Binding installed, and this data is persisted in InfluxDB. This way I can see historic gas prices in Grafana.

When the Telegram Bot answers the /tanken question, it appends the timestamp of the last gas prices update.

Online indicator for remote controllable power plugs in openHAB

Sat, 09 Jan 2021 23:46:00 +0100

Recently I installed a number of new power sockets (like this one). The Hue bridge can not only add each switch to a light group, but also reports each plug as a Thing in openHAB. There I thought it will be a nice touch if openHAB actually reports when it sees a device plugged in. The power socket has a LED which turns on when the plug is on. The Hue bridge reports OFFLINE and ONLINE. That’s useful.

The plan is to turn the LED light - and the power plug - on and off for a few second.

openHAB: reset DateTime in rules

Fri, 01 Jan 2021 18:26:00 +0100

In one of my openHAB rules I’m using a timestamp to track when an Item went offline. This is used in my monitoring to let the user (me) know how long the Item is already offline.

Background: we have a couple ChromeCasts in our network. When they are connected to a 5GHz Wi-Fi they are quite unstable and often loose the network connection. Usually the openHAB binding reconnects the device quickly, but it happens that the device stays offline. It might have something to do with the router, but nevertheless I want to know when things go offline.

openHAB: Configuration model '....rules' has errors, therefore ignoring it: no viable alternative at input '...'

Fri, 25 Dec 2020 10:50:00 +0100

The openHAB rule system is not very helpful by pointing out when it’s missing something, or when there is an error to actually point to the problem.

Add a Google Calendar to openHAB

Tue, 27 Oct 2020 22:14:00 +0100

openHAB can integrate Google Calendars. The functionality is kind of limited, it can only see the current and the next calendar event, but in my case that is enough. More about the use case in another blog post.

openHAB: faster loading of rules files

Sat, 24 Oct 2020 19:36:00 +0200

openHAB rules files are lazy loaded. When a rule is used the first time, the entire rule file is loaded and compiled, which apparently is single-threaded and takes a couple seconds. Even on a reasonable powerful Rasperry Pi 4. This happens both after restarting openHAB and after changing the rules file. It also means that whatever the rule in question is supposed to do has to wait a couple seconds when requested for the first time. Imagine you have a light switch, enter a room, press the switch, and it takes 5-10 seconds until the light comes on.

To work around this problem, I add a piece of code in all rules files which triggers an immediate action right after loading the file. This way the rules file is already pre-loaded (which again takes a couple seconds, but likely at a time when the rule is not needed right now).

Audio reminders in openHAB

Thu, 15 Oct 2020 21:20:00 +0200

A while ago someone mentioned “reminders” used in their home audio system, and I took that idea and implemented something similar in openHAB.

The basic idea is that I can send scheduled notifications to any audio sink openHAB is using, possibly more than one audio sink for one message. Also I want to differentiate between a simple audio sound, and text output.

Google Summer of Code 2020 - Intermediate status update

Fri, 21 Aug 2020 22:43:00 +0200

The three PostgreSQL projects for this year’s Google Summer of Code are on track, and making good progress. All projects expect to finish on time.

Performance Farm

The data gathering for performance farm members is completed, as well as the new implementation for the JSON data transfer. The project iteratively updated it’s goals, and adjusted for newly identified UI issues.

Current work centers around making the website more pretty and useful, as well as reducing the number of used JavaScript libraries. The next step is presenting the work to the PostgreSQL Community for broader feedback.

openHAB, Telegram Bot and quoting URLs

Wed, 19 Aug 2020 13:49:00 +0200

A while ago I integrated DWD warnings (Deutscher Wetterdienst) into our home automation system, and receive severe weather notifications ever since then. That works quite good, but it was missing a weblink with more details - or if you want to forward the warning to someone it would be useful to have a link to the warning as well. The DWD binding does not provide that piece of information, but it is easy enough to add - or so I thought.

Text-to-Speech in openHAB

Sun, 16 Aug 2020 17:28:00 +0200

In my ongoing endeavor to improve our home, a while ago I added a notification when the washing machine and the dryer are finished. The notification is send to a Telegram channel. Over the summer vacation I added a number new ChromeCast Audio devices (Google no longer offers the Audio CC, if you need one get one now). One is placed in the kitchen. Not only can I listen to music while eating breakfast, I can also output notifications, by using the CC as an audio sink in openHAB.

To make that useful, I decided to use a Text-to-Speech system. openHAB offers a couple different TTS systems, however most of them need a cloud integration, and therefore a working Internet connection. The “Pico TTS” works standalone, and was my favorite choice for this implementation.

openHAB and Tankerkönig gas prices + Telegram integration - Second iteration

Sat, 15 Aug 2020 18:25:00 +0200

In my previous blog post about “Tankerkönig” I explained the details of how to integrate this binding into openHAB and provide a Telegram interface.

Someone on the openHAB community forum pointed out that Telegram bots allow queries, where one can present the user with options, and the user only has to click on one of the options. That makes it easier to use, and less typing is required as well. I went ahead and implemented that.

Most of the implementation does not change, especially all the Things and Items are the same. The Rules change however.

Improve openHAB Rules response time

Mon, 06 Jul 2020 11:48:00 +0200

By default, openHAB only starts 5 threads to deal with execution of Rules. That’s not a lot, and if all threads are busy, rules have to wait until a slot is free. This results in slow Rule response time.

This can be improved.

openHAB: Turn display on and off for a Video ChromeCast

Sun, 05 Jul 2020 00:20:00 +0200

After figuring out if a ChromeCast is currently used, it was time to fix a long-standing problem. At home we don’t have TVs, just “dumb” displays, and stream content using ChromeCasts. However a video ChromeCast never really turns off, but keeps the display running, using a Backdrop app. This app keeps showing pictures on the display when the ChromeCast is not used otherwise, effectively preventing any powersafe mode.

That’s both annoying (who wants to have pictures shown in the living room or working room all night), and consumes energy. It’s also intentional by Google. So far we had to turn the display on and off manually, which is inconvenient.

openHAB: detect if a ChromeCast is currently used or idle

Sat, 04 Jul 2020 20:38:00 +0200

We have a couple of Audio and Video ChromeCasts in use. For an upcoming project I need to figure out if any of them is currently used. That is different for the Audio and the Video devices: the Audio just goes idle=ON, the Video devices however load the Backdrop app and show pictures when idling. Google for whatever reason does not want the attached monitor to go in powersafe mode. So much for saving energy …

Deutscher Wetterdienst notifications in openHAB and Telegram

Sun, 28 Jun 2020 17:32:00 +0200

The “Deutscher Wetterdienst” DWD (German Weather Service) provices a service which sends out alarms for upcoming events, like heavy rain, storm, blizzard, strong winds ect. This service is only available for Germany. And it has a binding for openHAB. Time to integrate this, activate a number of regions I’m interested in, and send notifications to our mobile phones.

openHAB and Tankerkönig gas prices + Telegram integration

Sat, 27 Jun 2020 01:03:00 +0200

In Germany, every gas station must report gas prices online, to the Markttransparenzstelle für Kraftstoffe. Businesses and users can then fetch this data and provide services. One of these companies is Tankerkönig, and there’s also a Binding for openHAB.

If you are interested in gas prices for certain gas stations, you need to sign up for a (free) API key, and figure out the IDs of the gas stations. For that go to this website, Position the blue marker on the location you are interested in, and then click on all the gas stations you want to include. Finally click on Tankstellen übernehmen - this will open a JSON with the data, from there extract the id (and possibly the other data as well).

openHAB and Telegram Bot

Mon, 22 Jun 2020 10:54:00 +0200

openHAB 2 comes with a Telegram binding which allows to run a Telegram Bot. This bot can both send messages to users and groups, and can receive commands and respond to them. That’s useful: your home automation system can send all kind of details to your mobile phone.

Monitor ChromeCast status in openHAB

Fri, 19 Jun 2020 13:10:00 +0200

I really like to monitor things, to catch issues early on. In our home we have a couple ChromeCasts, both Audio and Video. They are all connected to the openHAB system, Once in a while they stop working, and need to be restarted (unplugged and plugged in again). Unfortunately you usually only find that out when you want to stream something, and wonder why either the ChromeCast does not show up in the device list, or does show up but does not accept the media.

Google Summer of Code 2020 started

Thu, 18 Jun 2020 18:38:00 +0200

The PostgreSQL Project participates in Google Summer of Code (GSoC) 2020, with 3 projects. After the “Community Bonding” period finished last week, we are now in the active development phase - “Coding” as Google calls it. All three projects make good progress!

openHAB and HP printer

Thu, 18 Jun 2020 01:43:00 +0200

Recent openHAB versions come with a new HP Printer Binding, which is a big improvement over the more general IPP Binding for printers.

New OpenWeatherMap channels missing after openHAB upgrade from 2.4 to 2.5

Sun, 07 Jun 2020 22:54:00 +0200

A while ago I upgraded openHAB from version 2.4 to 2.5. That comes with the usual share of problems, but eventually I got it working.

openhab2: check if alive

Tue, 28 Apr 2020 15:42:00 +0200

As mentioned in my previous openHAB blog post: it seems to be too much to ask to have a reliable and working display in the kitchen.

Another problem I found is that the weather data occasionally does not update. Everything seems to work, no errors in the log, just no updated data. Of course this results in outdated weather info in the kitchen, and the threat that “someone” will buy a regular weather station and render my 7" Raspberry display useless.

Show raw openHAB Image Type in HABpanel

Sat, 22 Feb 2020 14:28:00 +0100

In our Home Automation system, I read weather data from OpenWeatherMap. I blogged about the implementation before. The weather data provides an icon which can be used to show the current weather:

Weather Forecast in openHAB based on OpenWeatherMap, using Ansible

Fri, 25 Jan 2019 21:00:00 +0100

After setting up OpenWeatherMap in openHAB, I had another project on my list: send a forecast for the next day.

That is rather easy to do with a Cron rule.

Install OpenWeatherMap in openHAB, using Ansible

Thu, 24 Jan 2019 21:00:00 +0100

Next item on my home automation todo list: weather, and forecast. No good system without that data!

After exploring the options which openHAB supports, I settled for OpenWeatherMap. Note: you need an account with OWM, the basic functionality is free, the paid options give you more and better forecast.

Notification when washing machine or dryer are finished, with openHAB

Fri, 06 Jul 2018 18:09:00 +0200

As part of my home automation project, I wanted the washing machine and the dryer to send notifications when they are finished. Both machines are in a separate room, and their alarm beeps are hard to hear in the other parts of the flat. Also because of the noise both machines make during operation, the door is usually closed.

After checking several options how to interact with the washing machine and the dryer (from listening to the audio signals to having light sensors glued over the status led, open the frame and install something inside, and a small cam with picture recognition), I settled with measuring the power consumption. Next step: find the right kit.

Add a FRITZ!Box to openHAB, using Ansible

Wed, 04 Jul 2018 14:31:00 +0200

Next step on my way to add home automation: the FRITZ!Box. Mostly for the current IP-address, and call information.

After some research it became obvious that more manual work is required, hence again something which can be automated.

BOOLEAN datatype with PHP-compatible output

Mon, 07 Jan 2008 12:43:31 +0100

If you use pure PHP (no database abstraction layer) with PostgreSQL, you may run into the problem that your BOOLEAN columns are not recognized by PHP but the value is instead returned as a string.