The Owad Laboratory

Configurig Let's Encrypt with DNS-01 challenge on Debian 10 Buster

While setting this up, I ran into a lot of issues with DNS service APIs not matching what was available in the buster repository and in other scripts that I tried. These are my notes on how to set up Let's Encrypt with a DNS-01 challenge, but the most important part is just knowing what works.

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Teargas in the walled garden: iOS is a threat to democracy

Apple's iOS App Store has been a tremendous success, generating over $100 billion in revenue since its inception. This is thanks in part to Apple's walled garden approach, which requires that all iOS software must be purchased through Apple's App Store. This approach has kept iOS relatively free of the malware that has plagued Android phones. Apple's screening of apps has resulted in a higher quality collection of software. It's a beautiful walled garden, in exchange for which, we give up control over what software we
can run.

More below the break.

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3d Printer Switch with Octoprint & SmartThings

My MakerGear M2 doesn't have a power switch, and it isn't convenient to turn off its power strip, so I connected it to an Iris Smart Plug with a little power switch on it. That solved the problem, and also let me turn the printer on and off with Alfred, but tempted me to intergrate with Octoprint. Octoprint has a plugin, System Command Editor, that lets you execute shell commands from Octoprint's Power menu. That makes the Octoprint part easy - now it's just a matter of controlling a SmartThings device from Linux.

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Raspberry Pi & Nexdock: Bluetooth via the command line

I received my Nexdock today and have begun configuring a Raspberry Pi 3 to work with it. I wasn't able to find current instructions for getting the Nexdock keyboard and trackpad to work with the Pi using the command line, so I've documented the procedure that I used.

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Uses for fishpaper

Fishpaper is an insulative paper that used to be common in antique radios. It's often used to insulate transformers.

The history of the name is pretty interesting. According to Alvin G. Sydor:


In 1729 Stephen Gray made the discovery of the conducting and non-conducting power of different substances. Gray found that by using woven silk served as an excellent insulator. Some years later it was found that the paper industry could provide what was equivalent to woven silk. Later it was discovered that if the paper was saturated with fish oil its ability as an insulator was much improved particularly when used in harsh environments and high voltages.


Recently, I've been using it for fast and cheap electronics cases. This is one of my backup servers:

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Cleaning handles with a brass wire wheel brush

I bought a Remline tool chest at an auction on Saturday. I've been wanting to get something a bit larger than my current chest, and I couldn't pass up these handles:

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Sonar trumps eTape

This post first appared on September 9, 2016.

I’ve given up on the Milone eTape entirely. I just couldn’t get it to work reliably. Instead, I decided to go with a RadioShack Ultrasonic Range Sensor as my backup method for detecting water. It’s mounted on the basement ceiling and will alarm when it detects an inch of water on the floor. The floor is sloped, so an inch isn’t nearly as bad as it sounds. It’s been working well. I’m leaning towards a pressure transducer for the main sensor.

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Calibrating Milone eTape

This post first appeared on April 29, 2016.

Milone's eTape is proving to be rather finicky. Per Milone's instructions, I have it installed in a 1" pipe, so that it can't stick to the sides. Readings fluctuate by up to 1/2", even with no change in water level. The eTape seems very sensitive to any sort of pressure. It needs to be suspended to give a proper reading. I neglected to suspend it during one test, and in an empty pipe, readings gradually reached 14", apparently just from the pressure on the bottom of the tape. Worse, according to this discussion, it appears that the eTape can be permanently damaged if it is submerged. That seems to contradict the Operating Instructions, which state:


The vent hole allows the eTape to equilibrate with atmospheric pressure and must not be submerged in the fluid to work properly. The vent hole is fitted with a hydrophobic filter membrane to prevent the eTape from being swamped if inadvertently submerged.


I've emailed Milone for clarification.



According to Chris at Milone, it's ok to submerge the vent hole, but submerging the connector tab will permanently damage the sensor - a detail I'd have thought would be worth mentioning in the Operating Instructions. The newer eTapes that come in tubes are sealed so that this isn't a problem. Chris says that bare eTape can be sealed by using RTV or Silicone II to completely cover the connector tab.

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