Hauke’s Projects

Playin' around with Electronics and Computers

Media Center Auto Shutdown and RTC Wakeup Based on tvheadend Recording Schedule

I created a script that runs via cron job that will power off my media center if it is not in use, but will program the real time clock (RTC) on the motherboard to wake up the system in time to run a scheduled recording, and/or to update the EPG data, and from that derive potential new or changed auto-recordings. To determine if the system is currently not in use, I

  • Check if the monitor is off
  • Check if any audio is playing, e.g.,  Spotify or KODI is playing anything
  • Check if the wireless keyboard is connected
  • Check if tvheadend is currently recording something

Also, the shutdown processing can be blocked by creating a flag file. If that file exists, no shutdown will happen.

The wake-up time is either the next recording time plus some allowance for boot time, or every 24 hours, whatever comes first. This makes sure that at least once a day the EPG is updated and tvheadend can update its auto-recording-schedule.

As a result, I reduce power consumption of the media center considerably.

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My Next Media Center Iteration: Intel NUC8i3BEH

My Raspberry Pi 4 based media center has some issues, which I was able to resolve by switching to an Intel NUC8i3BEH platform. I was able to make the device quiet despite of its fan, and set up everything to have live TV and PVR, a web browser, Spotify and other DRM content in a very usable and performant setup.

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Soil Water Sensors: Problems with the Ubiquitous DFRobot Capacitative Sensors

Capacitative soil moisture sensors based on this DFRobot-design (and its successors) can be found in numerous blog articles about irrigation automation. For me, they do not work out for two reasons: a) A notable temperature dependency of the measurements, and b) a high failure rate after a few months to a few years. I decided to adopt the concept of my Simple Capacitive Water Sensor for a Water Container for soil moisture measurement, which turns out to work well.

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European WordPress Bloggers beware: “Abmahnwelle” due to Google Fonts!

WordPress admins are currently sued for using Google Fonts directly from the Google servers without correctly informing users about the data collection by Google. I give a few hints on how to protect yourself against this. Disclaimer: I’m not a Pro in legal regards, so take everything I say with a grain of salt.

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Simple Capacitive Water Sensor for a Water Container

From simple, standard electric cable I built a capacitive sensor to assess the water level in my water container. While the circuit was replicated from this blog (thanks for sharing!), I’d like to share how I built the actual capacitor.

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Lessons Learned: Measure Water Levels in a Barrel with SR04-Type Sensors

Using ultrasonic distance sensors I monitor water levels for my garden irrigation system. I have an underground rainwater cistern and a wooden barrel as an interim water storage in the sun to have the water warmed up before use. I started off with the classic HC-SR04 ultrasonic distance sensor, but it turned out to be a bad idea for the warm water barrel: Moisture and temperatures up to 40°C in the summer sun made the sensor rot within half a year down to complete failure. I switched to AJ-SR04M watertight sensor (which seems to be very similar to JSN-SR04T which is often also mentioned on the internet). This has a higher minimum distance (~20 cm vs. ~2 cm), and a much larger opening angle (45° to 75° vs. 15°) as compared to the HC-SR04, and in this post I describe how I dealt with that.

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Quick Thing: TARDIS Housing for Raspberry Pi modded for Raspberry Pi 4

This is just a quick note that I updated my Tardis housing for my media center to now hold a Raspberry Pi 4. The new version features:

  • An improved “POLICE public call BOX” sign
  • A hole for a 5 mm LED in the top for a shining light
  • The necessary holes for USB-C, 2x Micro-HDMI and Audio out
  • A removable top

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Quick Thing: Case for Diamex All-AVR Programmer

The Diamex/Tremex All-AVR programmer for ATmel microcontrollers comes as “naked” populated PCB, no case, no protection against shorts or other damage. I created a case for it, with the following design criteria:

  • Protection against accidental shorts as good as possible.
  • Easy access to the jumpers that control the various operation modes.
  • “Park position” for the jumper that de/activates the external power (since it is often in “off” position and can easily be lost).
  • LED signals need to be visible.
  • Uses the existing mounting holes.

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Replacing Fabtotum Hybrid Head v1 Hotend with E3D Lite6

I replaced the stock hotend of the Fabtotum Personal Fabricator Hybrid Head v1 by an E3D Lite6 hotend (The full metal V6 should work the same way). In this post I describe the steps to remove the old hotend, get in the new hotend and the simple modifications to the firmware that were required.

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Quick Note: Modify the WordPress Comments Cookie Consent in an Update-stable Way

It always bothered me that I could not modify the text (“Save my name, email, and website in this browser for the next time I comment.”) of the cookie consent checkbox in the WordPress comments section to explicitly mention that it uses cookies. Continue reading “Quick Note: Modify the WordPress Comments Cookie Consent in an Update-stable Way”

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