Parking spaces in buildings are as small as possible to avoid wasting precious real estate. Furthermore, such parking spaces are often surrounded by concrete pillars or delimited by walls, making it difficult to move a car into such a tiny reserved space without scratching its precious metallic paint. Add to this that cars only get bigger and you will understand the need for an electronic parking aid. Here is a simple solution based on cheap ultrasonic transceiver modules.

The amount of negative oxygen ions in the ambient air seems to affect the psychological and physical state of many people. The air in the mountains and near the sea contains relatively high numbers of negative ions compared to elsewhere and this is one of the reasons that you feel better in this type of environment. You can improve the air quality at home too, when using the ioniser described in this project.

Most of the time simple solutions are the best. “Keep it simple, stupid” or KISS is a well-known but often ignored design principle. Not so for this project which consists mainly of clever wiring and a bunch of connectors. What can you do with it? Not only does it allow you to get out of the wallwart phone charger mess by providing inputs for several plug types but it also lets you easily attach a volt- and ammeter to see what's happening -- and why. Hide it all in a sturdy little box and what you have is a handy adapter & test tool.

Here is a nice project using a classic chip from the past: the good old voltage regulator uA723. According to Wikipedia this chip was designed by Bob "every-idiot-can-count-to-one" Widlar and commercialised by Fairchild Semiconductor in 1967. Now, 50 years later, we encounter this chip in its metal-can version in a digitally controlled current source, showing that if, like the Rolling Stones, you feature excellent input and load regulation, you can have a long career under the spotlights.

Imagine you want to measure soil temperature. For ease of use and precision an electronic thermometer with an easily readable display would be nice. The sensor must be such that it can be stuck in the dirt, dry or humid, and while you’re at it, what about being able to measure the temperature of a roast on the BBQ? Enter the Resistance Temperature Detector or RTD together with a precision resistance meter.

I love time; the more I can have of it, the better. Unfortunately our time is limited, but running tasks in parallel feels as if we have more of it to spend. Timers are important in parallel processes as they can provide start, pause and stop signals without human intervention. The 555 is the electronics engineer’s default timer but, as versatile as it may be, it isn’t suited for every application. Here is a project that tries to remedy that.

Before the rise of Arduino, microcontroller development boards had on-board peripherals like pushbuttons and LEDs, a display, one or more potentiometers for analog signals, extension connectors, etc. and, of course, a decent power supply. The goal of these boards was to provide an easy way to start learning the microcontroller without having to solder or add other components. The AVR Playground – an open source, open hardware project – was designed with this in mind, and extended with things from Arduino that we have learned to appreciate.

Connecting devices to the Internet, that is what IoT is all about. To do so you need some sort of interface and that is where the GoNotify project comes in. This project brings you a low-power and secure platform comprising of an ATmega328PB microcontroller and an ESP8266 Wi-Fi module enabling easy connection to online cloud-based data collection services like AllThingsTalk. MQTT client or secure HTTPS with REST, in sleep mode the interface only consumes 10 uA while a universal connector permits the connection of sensors and actuators just like you need them.

For those who want to adjust the volume of the music they listen to with analog hardware but do not want to invest in servo-controlled potentiometers here is a compromise in the shape of a so-called ‘Digitally-Controlled Analog Volume Control’. It has a serial control interface, selectable zero crossing detection and a mute function. This design was intended for use with a Raspberry Pi running Volumio, but it can be used with virtually any audio source. It even adds RC control.

Over time quite a lot of projects have been published on Elektor Labs. The recent projects and those that get updated frequently remain visible at the top of the project list, but there are many interesting old projects in various states that we tend to forget. So, going back in time, here is one that may be as useful to you as it was to the author when he posted it: a simple USB charger for 2S LiPo batteries. Charging one cell from a USB port is easy, but two cells require more than 5 volts. It is even possible to adapt the circuit for three cells.