February 2021

4G-based Remote Monitoring Station

This 4G Arduino-based system enables remote environments, vehicles or properties to be monitored and will send a wireless alert via 4G (mobile data) whenever your choice of sensors, switches or voltages is triggered. It can monitor just about anything, provided that there is an Arduino library to interface with the chosen sensors. Originally designed to warn of the presence of rescue wombats(!) in the Australian bush, typical usage applications include monitoring a house or holiday home, outbuildings and stables, caravans, boats, or a cherished car or truck: parameters might include low battery voltage warning, flooding, smoke alarms or anti-theft/ intruder detection.

The project also offers continuous data logging via 4G as well as sending text messages for drawing your attention to unusual situations that have been detected in the monitored environment.

The Remote Monitoring Station is based on a 4G shield designed by DFRobot which utilises a SIMCom SIM7000E module to provide the necessary 4G communications. Both SMS and mobile data are utilised but voice calls are not available.  The ThingSpeak cloud-based IoT data collection service is also utilised. The project has very low (microamps) quiescent current consumption. Solar charging options are included. Very comprehensive instructions for set up, installation and testing are provided in this month’s article.

Before commencing construction, please research which mobile frequency bands (3, 8, 20 and 28) are supported in your locality to ensure the SIM7000E (= European version) Shield is compatible with them.

Low-distortion DDS Signal Generator

This two-channel DDS (Direct Digital Synthesis) audio signal generator produces very low distortion sinewaves as well as triangle and square waves, pulse trains and noise. It operates via a rotary encoder and is equipped with an informative graphical LCD. The project draws on earlier project hardware – the DSP Active Crossover/ Parametric Equaliser (Jan through March 2020 issues).

  Surface mount components are used and very good soldering skills are needed to complete this project successfully.

Micromite Indoor ‘Poor Air Quality’ Monitor

This Micromite application is designed to measure the concentration of Volatile Organic Compounds (VOCs) that are present in ambient air. VOCs are produced by a wide range of materials and affect the quality of air, and may contribute to so-called Sick Building Syndrome or other ailments. The project uses a pre-made precision MOX detector together with a Micromite LCD Backpack. The Air Quality Monitor displays on the LCD a graph of VOC concentration measurements in ppm/ppb, and also has menu-driven setup options.

USB Logic Analysers

In the latest instalment of our series on Using Cheap Asian Electronic Modules, an 8-channel USB logic analyser is put under the magnifying glass. The product in question is a budget-priced alternative to professional Saleae Logic units costing far more. How well does it compare? Check our feature to find out!

Make it with Micromite
Part 25: MMBasic, Micromite and Maximite varieties

An extremely comprehensive comparison of the Micromite family of controllers and its MMBASIC software is offered this month. If you have never ‘coded’ a microcontroller before, the Micromite offers a very elegant and simple solution to producing embedded controllers ready to tackle a very wide variety of applications. The popular Micromite is an ideal starting point for electronics enthusiasts wanting to boost their project’s capabilities and it enjoys excellent support as well.

Practically Speaking
Restoring old equipment (Part 2)

More practical hints and tips about restoring vintage electronics gear, and the story behind popular amplifier circuitry.

Electronic Building Blocks

An idea for a cheap DIY wireless phone charging pad is suggested this month.

Also in this issue:

• The Fox Report – following up on a smart meter advertising complaint
• Techno Talk – some bogus technological scams uncovered – you have been warned!
• Net Work – Amazon’s latest Fire TV Stick, Devolo’s new Wi-Fi repeater and electric vehicle charging stations
• Audio Out – Theremin Audio Amplifier (Part 4) – this month some different design strategies are explored.
• Circuit Surgery – Simulation issues with a digital divide-by-two circuit
• Max’s Cool Beans – Flashing LEDs and Drooling Engineers (Part 12)

In next month’s issue:

Programmable Thermal Regulator, Nutube Guitar Overdrive and Distortion Pedal, Tunable HF preamplifier with Gain Control; Kickstart: Part 2 – RFID tags