The trigBoard is an IoT project that does one thing – it pushes you a notification triggered by a digital input. Well, it’s much more than that, but this is the inspiration. I wanted to design a WiFi board that essentially sleeps most of its life, but when that door switch, flood sensor, motion sensor, etc.. gets triggered, I just want a notification immediately on my phone. And that’s about it… a perfect IoT device in the background doing its job.
I’ve been doing some LoRa projects lately in order to learn as much as I can about this exciting new radio technology (see this LoRa mesh networking project and this LoRa weather station). ATmega328-based Moteino modules work great for a lot of projects, but I wanted a LoRa node with more processing power, more memory, and an onboard GPS receiver. The ATmega328 is just too constrained with memory — I’ve outgrown it. I really wanted a LoRa board with an ARM Cortex microcontroller like the SAMD21. This is the microcontroller used on the Arduino Zero. So, my ideal board is a SAMD21 with LoRa radio module and GPS receiver, all programmable with the Arduino IDE.
But, where is such a board? I could not find one so I decided to design and make one myself.
App note from Coilcraft on the design and construction of common mode filter inductor. Link here (PDF)
Noise limits set by regulatory agencies make solutions to common mode EMI a necessary consideration in the manufacture and use of electronic equipment. Common mode filters are generally relied upon to suppress line conducted common mode interference. When properly designed, these filters successfully and reliably reduce common mode noise. However, successful design of common mode filters requires foresight into the nonideal character of filter components — the inductor in particular. It is the aim of this paper to provide filter designers the knowledge required to identify those characteristics critical to desired filter performance.
Coilcraft’s app note on temperature rise due to losses on inductors and transformers. Link here (PDF)
Core and winding losses in inductors and transformers cause a temperature rise whenever current flows through a winding. These losses are limited either by the allowed total loss for the application (power budget) or the maximum allowable temperature rise.
For example, many Coilcraft products are designed for an 85°C ambient environment and a 40°C temperature rise implying a maximum part temperature of +125°C. In general, the maximum allowed part temperature is the maximum ambient temperature plus temperature rise. If the losses that result in the maximum allowed part temperature meet the power budget limits, the component is considered acceptable for the application.
What are you thinking — I am not trying to break any world record? My XYL asked me that question today — why are you building another rig? Followed up by a snide comment that I had so many rigs now why do I need another one. Well the answer plain and simple because I can!
For the longest time in the late 60’s early 70’s my success rate with homebrew SSB transceivers was miserable. At that time I lacked the more sophisticated test gear and let’s face it some of the technology wasn’t that great. Crappy Analog VFO’s were high on the list of impediments! I also had to work and to give a fair share of my time to the family — it is that balance thing.
But today that is all changed –better test gear, better technology like Digital VFO’s and a bit more time. The latest project is to demonstrate that some of the components out of boat anchors can indeed be reworked to provide a very modern, very capable rig.
Jesus Echavarria made this battery monitor and wrote a post on his blog detailing its assembly:
Here’s one of the design I do last year for a client. He wants to measure the voltage of a car battery and set a couple of alarms when voltage falls below a defined values. Also, he wants to put the device in the relay box of the car, so the design needs to have a relay form factor to easy integration. So, after a couple of iterations, here’s the final design of the battery monitor.
For a project I need to program a few microcontrollers in the same circuit. This meant I needed to plug the programmer around on the board a lot. This got annoying very fast. Therefore I decided to make a switch box. In my junk pile I found an old switch of a, parallel port switch. This has 4 positions and a lot of contacts. For the ICSP I only need 3. However in some circuits the supply voltage is not common. Hence, I chose to also switch the power supply connections. For the connections to the circuit boards I used DIN connectors, for the simple reason I have lots of these.
App note from MAXIM Integrated on very compact PMIC using only single inductor to drive three independent switching regulators. Link here
Small form factor and minimal power loss are key criteria for internet of things (IoT) hardware, particularly wearables. Meeting these criteria typically involves some tradeoffs. For example, to meet a specific power consumption goal, a designer usually would have to compromise with an increase in design size.
Anthony Lieuallen made this custom power supply and wrote a post on his blog detailing its assembly:
You might not truly be an electronics nerd until you build your own power supply. Either way, I’ve finally passed that threshold. As I’ve mentioned previously (and previouslier), I’ve been working on mine — very slowly, off and on — for most of a year. The bare start came with a guide posted to Hackaday about using nichrome wire to heat and bend acrylic plastic in straight lines, to make cases.