Engineering in January: DIY Music Synthesizer, Mini Z80, and More

In 2021, we celebrated Elektor's 60th anniversary. In the coming months, we will continue the celebration by highlighting some of the engineering team's favorite engineering articles and DIY projects from past. This month, we consider some of our favorite articles from previous January editions of Elektor magazine. We take a look at a GUI for for ESP32, a neat music synthesizer, a mini Z80 project, and more.

GUI with Touch for ESP32, RPi & Co. (January 2020)

LittlevGL is a library under the MIT license that you can easily adapt to various displays and controllers. Would you like to give it a try? In this article, Elektor engineer Mathias Claussen offers a nice demo using an ESP32 board and a touch LCD.
  "You learn most when you try something hands-on. Therefore, the use of the library within Elektor’s weather station is demonstrated here," Claussen explained. "The goal is a GUI suitable for touch operation. We will even realize a multi-page display for data. But this requires hardware."

J²B Synthesizer: An Open-Minded Digital Music Platform (January 2015)

The J²B Synthesizer project was born after Elektor engineer Clemens Valens discovered the Atmegatron music synthesizer from Soulsby Synthesizers. The design's specs include Monophonic 9-bit synthesizer, 32 waveforms, 15 filter types, LFO with 16 waveforms, 6 live controls, MIDI, NXP LPC1347 32-bit MCU, two output channels, and more.
  “Looking at the schematics of the synthesizer, you will see no surprises,” Valens wrote. “I managed to use all the available I/O ports. The eight rotary encoders take up 16 I/O ports, two per encoder. The bunch of resistors surrounding the six live controls serve the purpose of flexibility. Indeed, by using the right resistance values it becomes possible to replace such a rotary encoder by a potentiometer because one side of these encoders is connected to an input of the MCU’s analog-to-digital converter (ADC).”

Arduino on Course: A Plant-Watering Supervisor for Communal Use (January 2013)

Most of you recognize David Cuartielles as the co-founder and co-creator of Arduino. Back in 2012 and 2013, he wrote a series of articles for Elektor. In the January 2013 edition, Cuartielles presented a hands-on experiment, a plat-watering supervisor.
  "I didn’t want the project to be too complex; therefore, I decided that it should be focusing only on the human aspects of watering a plant and it should not involve measuring the humidity of the plant’s soil or any other ambient conditions around the plant itself," Cuartielles wrote. "Neither did I want to make anything connecting to the Internet to remind me about watering the plants (the project Botanicalls is doing precisely that, it tweets a message when the plant is in dire need of water). I just wanted a device to let my neighbors check out when was the last time someone took care of the plants. So I thought about the chess clock paradigm. Players have to press a button on the clock at the end of each move to pass the turn to their opponent. My idea was to create a clock that would offer the same interaction. Once someone waters the plant, he or she presses a button and passes the responsibility to someone else. When pressing yet another button, the machine will indicate just how long the plant hasn’t been watered."

Practical Neural Networks (January 2003)

Think artificial neural networks are new technologies? Think again. Elektor began covering the topic in 2003 with an interesting article series titled "Practical Neural Networks." In the first part of the series, Chris McLeod and Grant Maxwell introduce neural nets, cover the history, and dive into the some basic math and coding.
   “You can implement neural nets in hardware, either analogue or digital,” they noted. “Three simple amplifiers weight the inputs; these have to have electronically adjustable gains if the network is to learn in real time. The output is then summed and the threshold is applied by a comparator. This type of circuit has been built using discrete components like Op Amps and as part of an Integrated Circuit. The disadvantage of this approach is that it requires a lot of components, should there be many neurons.”

Mini Z80 System (January 1992)

The Z80 8-bit microprocessor is a classic. Inexpensive and easy to program, it has enabled thousands of pro engineers and makers to get creative at their workbenches. In January 1992, Elektor presented A. Rigby's innovative Mini Z80 System, which was a no-frills mini computer system based on the famous CPU with I/O and ROM. The main specifications: a Z80 CPU, 2-MHz clock, 8K ROM (EPROM 2764) or 16K ROM (EPROM 27128), 2x8 bit input/output, and the option of 8K RAM extension.
  "Probably the most remarkable feature of the present computer board is the absence of RAM (random access memory)," Rigby explained. "This is unusual, but in many cases the internal registers of the Z80 can function as RAM equally well. Omitting a RAM IC then allows us to cut down on components (cost), and save board space ... The Z80 CPU (central processing unit) uses I/O-mapped input-output operations, which means that the CPU works with different addresses for the memory and the I/O blocks. The present system has four I/O addresses, although two further blocks of four addresses may be selected via the two I/O ports."

Universal Control for Stepper Motors (January 1987)

The January/February 2022 edition of Elektor Mag features a handful of articles about motor control, a topic we’ve been covering for decades. Check out our January 1987 article, “Universal Control for Stepper Motors,” to get a feel for what motor control enthusiasts were focused on back when a gallon of gas sold for $0.89 (£1.89).
  "As the stepper motor control board is essentially only a peripheral device, the computer — or more precisely the software — determines the movements of the stepper motor spindle. The key to the driving of the motor(s) is the 8-bit control word sent to the board via the computer's parallel output port."

Induction Loop Paging System (January 1982)

In the early 1980s, short-range paging systems were often used in large buildings. In the January 1992 article, "Induction Loop Paging System," Elektor presented a design that could be used as a "wireless" connection for radio or TV sound, an alarm, a doorbell extension, or an intercom system. The image below, which appeared in the article, depicted the basic idea behind the induction loop paging system. The lines of flux are perpendicular to the actual induction loop.
  "An induction loop paging system provides wireless transmission of information and can be used as a personal paging system in factories, warehouses, etc. or as a hearing aid in cinemas, theatres, etc. To be viable, the system should be very economically priced. The requirements for constructing such a system are: a (powerful) audio amplifier; a loop of wire that marks the periphery of the area to be covered; a sensitive audio amplifier for each 'participant'. The latter must be able to sufficiently amplify the energy produced in a small pick-up coil."

More Engineering to Come

Join us in February when highlight some more classic Elektor projects and engineering tutorials. And don’t forget to share your thoughts in the comments section below. The engineering continues!