Add a Watchdog Timer to Your Microcontroller

Although most modern microcontrollers have an internal watchdog timer, that may not be safe enough for the system to rely on it. The built-in watchdog timer can reset the MCU but it cannot perform a power cycle. An external watchdog controlling the MCU’s power supply may be a better solution in some cases. There are dedicated ICs for that, but you can also make one yourself based on a 555 timer IC.

When using one or two LEDs as indicators in a circuit, their respective brightness is not the most important thing in the world. If, on the other hand, the goal is to build a LED-based lighting system for homogeneously illuminating for instance a painting or another surface, then the individual brightness of each LED is important. After building this tool, handpicking LEDs for brightness becomes much easier.

The Six Digit Nixie Clock we published in Mai 2016 was greeted with a lot of enthusiasm. One of its users, F1Andy, posted a design for an upgrade to add WS2812-based multi-colour backlighting to the clock. He reworked the software too. Now it has alarm functions and it can display the date. To extend the life of the Nixie tubes dimming and anti-cathode poisoning was added as well. Note that some of these new functions require minor hardware modifications of the clock. An official Elektor PCB for the multi-colour backlight will be available soon.

RC models like race cars and boats can be had very cheaply. Because of their low price they only feature binary controls like Left/Right and Go/Stop. However, an enthusiastic engineer can easily transform these controls into proportional ones if there is enough free space inside the model. Of course, it takes some fiddling and hacking to get it right, but that is exactly what you like about this hobby.

Although the example used in this project is probably only useful for people travelling through the Netherlands (you know, the capital of Denmark), it does show how to use a microcontroller to extract data from a website. In this case it is an ESP32 that requests and parses JSON data and then displays the information of interest on a small OLED display.

We get many questions about Arduino. Most of them have been asked before, and some several times. There is, of course, a countless number of webpages out there which treat most of these questions in some way, but it means digging through forums and blogs to find the answers. As this can be quite time consuming, Elektor Labs decided to compile their own Frequently Asked Questions (FAQ) for Arduino and write down the answers to them once and for all. So, before asking us, check our Arduino FAQ to see if the answer to your question is already there.

The Raspberry Pi is getting more power-hungry with every new version. Actually, little by little it seems to evolve into a PC. So then, why not use PC components to extend it? You can start by replacing the tiny phone charger you used till now by an ATX power supply capable of delivering a few hundred watts. And while you're at it, why not add some features like a power switch and temperature control?

Even though an electronic load is not a tool many people will use daily, it is very practical to have one in your lab just in case. Testing a power supply is probably the first thing that comes to mind, but what about that AC heater regulator that isn’t functioning too well? This electronic load can test it as it is suitable for DC as well as AC.

Many people care about the environment they live in. It's not about the speed of your Internet connection or other mundane problems, but about particulate matter and radioactive elements floating in the air. This Environmental Monitoring System allows you to keep an eye on what is going on around you.

How do you power a highly reliable LoRa gateway that can be trusted not to trash its SD card and can be remotely located and managed? With this Power over Ethernet (PoE) powered uninterruptible power supply (UPS). A couple of 25-farad supercaps provide enough backup time to cover ten seconds of power outage plus another fifteen seconds to cleanly shut down the Pi if necessary.