Picking the Right Sensors for Home Automation

Imagine that you’re starting a project where you need to measure temperature and humidity. That sounds easy in the abstract, but choosing a real device out of many involves digging into seemingly infinite details and trade-offs that come with them. If it’s a low-stakes monitoring project, picking the first sensor that comes to mind might suffice. But when the project aims to control an AC system in an office of temperature-sensitive coders, it pays to take a hard look at the source of all information: the sensor.

Continuing a previous article I would like to use that same BMaC project from that article as a way to illustrate how even a couple of greenhorns can figure out how to pick everything from environmental sensors to various actuators, integrating it into a coherent system that in the end actually does what it should.

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Go Subterranean With This DARPA Challenge

Whether it comes to rescuing people from a cave system or the underground maze of sewers, tunnels and the like that exist underneath any major city, having accurate maps of the area is always crucial to know what the optimal routes are, and what the expected dangers are. The same is true for combat situations, where such maps can mean the difference between the failure or success of a mission. This is why DARPA last year started the Subterranean Challenge, or ‘SubT’ for short.

This challenge seeks new approaches to map, navigate, and search underground environments during time-sensitive combat operations or disaster response scenarios, which would allow for these maps to be created on-demand, in the shortest amount of time possible. Multidisciplinary teams from the world are invited to create autonomous systems that can map such subsurface networks no matter the circumstances.

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Transcending the Stack with the Right Network Protocol

The increase in network-connected devices the past years has been something of a dual-edged sword. While on one hand it’s really nice to have an easy and straight-forward method to have devices talk with each other, this also comes with a whole host of complications, mostly related to reliability and security.

With WiFi, integrating new devices into the network is much trickier than with Ethernet or CAN, and security (e.g. WPA and TLS) isn’t optional any more, because physical access to the network fabric can no longer be restricted. Add to this reliability issues due to interference from nearby competing WiFi networks and other sources of electromagnetic noise, and things get fairly complicated already before considering which top-layer communication protocol one should use. Continue reading “Transcending the Stack with the Right Network Protocol”

The Joy Of Properly Designed Embedded Systems

The ages-old dream of home automation has never been nearer to reality. Creating an Internet of Things device or even a building-wide collection of networked embedded devices is “easy” thanks to cheap building blocks like the ESP8266 WiFi-enabled microcontroller. Yet for any sizable project, it really helps to have a plan before getting started. But even more importantly, if your plan is subject to change as you work along, it is important to plan for flexibility. Practically, this is going to mean expansion headers and over-the-air (OTA) firmware upgrades are a must.

I’d like to illustrate this using a project I got involved in a few years ago, called BMaC, which grew in complexity and scope practically every month. This had us scrambling to keep up with the changes, while teaching us valuable lessons about how to save time and money by having an adaptable system architecture.

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Buy Your Very Own Commercial Flight Simulator

If you happen to live near Phoenix, Arizona, have a spare US$10,000 or so kicking around, and have always fancied your own true-to-life commercial flight simulator, today is your lucky day. With just over a week to go on the auction, you can bid on a used flight simulator for a Bombardier CRJ200 regional jet airliner.

The CRJ200 jet was produced between 1991 and 2006, first being introduced in 1992 by Lufthansa. It’s a twin-engine design, with about 50 seats for passengers. With a length of more than 26 meters, 12,500 km (41000ft) ceiling, 785 km/h (487mph) cruising speed and a range of around 3,000 km (1864 mi) (depending on the configuration), it offers plenty of opportunities for the aspiring (hobbyist) pilot.

The auction stands at the time of writing at $4,400 offered and lasts until Monday, January the 28th. Local pick-up is expected, but the FAA-certified simulator comes complete with all of the manuals and the guarantee that it was 100% working before it was disassembled to ready it for auction. Just make sure that you have somewhere to put it before putting in that bid, and you could be the owner of a rig that would leave some of the best we’ve seen so far behind in the dust.

The Lost Art Of Steam Heating

We got pointed by [packrat] to a 2015 presentation by [Dan Holohan] on the history and art of steam heating systems. At the advent of central heating systems for entire buildings, steam was used instead of water or air for the transport medium. These systems were installed in landmark buildings including the Empire State Building, which still use them to this day.

A major advantage of steam-based heating system is that no pump is required: the steam will naturally rise up through the piping, condenses and returns to the origin. This can be implemented as a single pipe where condensation returns through the same pipe as the steam, or a two-pipe system where the condensate returns through its own pipe.

In the presentation, Dan walks us through his experiences working on many of these steam heating systems in major US buildings, the types of systems, fixes implemented by engineers long since dead and the particularities of maintaining these systems.

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Making PCBs With A Cutting Plotter

[LudwigLabs] is creating PCBs using copper foil and a cutting plotter (vinyl cutter). In this approach, it’s an additive process where instead of removing copper from a copper-clad board, the traces are cut out of copper foil and transferred to a solid backing surface (cardboard, fiberglass, etc.).

While similar to the use of copper tape laid out by hand, as covered by us last year, the big advantage of using a cutting plotter is that it allows one to create much more complicated traces similar to those you would expect to see on a factory-made PCB. Since cutting plotters translate a 2D design into very precise movements of the cutting blade, this allows for sharp angles and significantly thinner traces, allows designs from EDA software like KiCad or Altium to be quickly translated to physical boards.

Enterprising hackers might consider the possibility of using this approach to make two-sided, and even multi-layered boards. The copper is produced separately from the substrate which opens up the potential for using uncommon materials like glass or paper to host the circuits. The main limitations are the transferring of (very delicate) copper structures and creating vias without damaging the traces.

As a comparison with traditional PCB fab processes, the photo exposure and etching (or laser exposure and etching) process requires the creation of masks, UV exposing a board, etching, cleaning and so on. The simplicity of copper foil traces has led to many experimenting with this approach. Would you want to use this additive process, or are there refinements or alterations you would make?