March 11 2025 Home Assistant, yaml, AWK

Brian described how he had tackled a problem when parcels are delivered; he normally only gets advice of the delivery shortly before it happens and he may be too far away from home to return in time for the delivery.

Home Assistant manages the door control which sends a tremolo which is AC and has to be converted to DC. He can set this signal so that it will automatically open the door. The ESP8266 manages the relays which require 5 volts; however, the ESP8266 has no 5 volt output, only 3.3 volt pinouts. So he takes 5 volts from the lead to power the relays.

February 11 2025 tailscale, gocryptfs, ‘Le potato’, Orange Pi, U-Boot, x86-64 levels

Steve gave a presentation on tailscale comprising a summary and a demonstration. Tailscale provides an overlay network for WireGuard which is tricky to configure and use. Tailscale creates Tailnet, a virtual/overlay network of hosts, with a coordination server through which to register clients. It provides NAT traversal and can set up a relay if that is not possible. Security is provided by asymmetric keys with public keys being shared by all clients.

January 14 2025 3D printers, Proxmox, Geograph, ash

David reported that ATC_MiThermometer cannot flash Xiaomi thermometers any longer even though the devices look exactly the same as the earlier ones but require soldering.

He had had to buy a new Raspberry Pi 3+ with heatsink after his existing one overheated while 3D printing a battery holder. He had got a second printer from Kriss and Shi which is 24V and so there is nothing to power a 12V fan!

There are loads of options for battery holders of different sizes; you just load the STL (stereolithography) file; they look like a beer crate, stack like a beer crate and take 5½ hours to print.

December 10 2024 Python GUIs, PPDs, Raspberry Pi Pi500

Bernie demonstrated how he had developed a Python GUI to provide a service needed in an astronomy context to an Instrument Neutral Distributed Interface (INDI). He needed a general purpose client but using ncurses was impractical as it doesn’t work in Windows. He first showed an example using ncurses running locally on a Raspberry Pi which turned an LED on and off by talking to the service.

When you import a GUI framework, you get a lot of widgets; he demonstrated with an example of the code used with Tkinter, the standard Python GUI, turning an LED on and off. The advantage of using the Gtk libraries is that they are on the Raspberry Pi and they are easy to install in Windows.

November 12 2024 Mariadb permissions, databases, visually impaired users, Stellarium

Mike had had problems in connecting MODX with mariadb. John wondered if this was a permissions problem as mariadb changed the way it handles permissions as set out during the meeting on 13 April 2021. Now there are five ways of handling permissions:

October 8 2024 Image sharing, Python, SD cards, SDR, AAX, Proxmox, Ventoy

Steve asked about photodisplay software; John mentioned that David had done a session on that many years ago when he had mentioned Panoramio [acquired by Google in 2007 and closed in 2016], Picasa [acquired by Google in 2004 and closed in 2016] and the bargain basement ImageShack [moved to a subscription based service in 2016] and Photobucket [moved to a subscription based service in 2017] but he did not know how many were still in action. [There is a list of active image-sharing websites on Wikipedia].

September 10 2024 Birthday review, Wuthering Bytes, uv

John gave a presentation marking our 16th birthday on topics covered over the past year. David queried whether the Raspberry Pi pop-up shop had closed and John said that he assumed it had as no-one had mentioned it for several months [it no longer appears in the list of shops in Victoria Centre]. David also said that an errata had been released relating to the GPIO pins on the RP2350 because a supplier had messed things up; unfortunately, if a pin is in an undefined state, it does not go high or low. Rather it creeps up high when you expect it to go low which affects some boards. This is mainly a problem for manufacturers rather than for hobbyists as there are workarounds and it might be fixed.

August 13 2024 Mars Rover, Pico 2 and RP2350, LyX 2.4

Bernie gave a talk on the Mars Rover’s unique suspension incorporating a rocker arm, bogey and differential cam mechanism which keeps the payload at the same height while keeping the wheels on the ground all the time. It is all done with linkages which ensure that the movement of one wheel up or down is matched by corresponding pressure on the other wheel to keep it in contact with the ground. This YouTube video is an animation of the action while this YouTube video of a scale model of the rover suspension demonstrates its operation.

July 9 2024 AWK, Alexa, Plasma 6.1

Brian commented that nmap is not working as it used to [as from 7.90, it changed its licence and is no longer considered free; the alternative would appear to be ZMap].

Darren is working on a demonstration of AWK, the data extraction program. He demonstrated some examples of basic conditional printing and of combining patterns to achieve more sophisticated results.

June 11 2024 Python+ncurses, Raspberry Pi Ltd, EMF Camp, Alexa

Bernie has been working on a console based interface which he can use with SSH to manage devices controlled through the Instrument Neutral Distributed Interface (INDI) using Python and the ncurses library.

In the specific example he demonstrated, he sent a new target to change the temperature. But in practice, by setting vectors to be values, you can have the controls to manage multiple devices, as long as there is a driver for the device. It can be used with any instrument though Bernie has in mind those using INDI.