April 2018

Spring Reverberation Unit

A modern take on a project for anyone yearning for the real reverb sound of an electric guitar. Instead of digital processing this design uses a traditional spring unit at its heart to recreate the classic sound of acoustic reverberation.

Classic spring reverb ‘tanks’ are still popular on auction sites so we suggest several suitable ones that can be utilised with our project’s audio analogue discrete processing circuitry. A project that will be welcomed by traditional guitarists everywhere!

Touchscreen DDS Signal Generator

This Direct Digital Synthesiser (DDS) function generator module is based upon around a Micromite LCD Backpack, and can produce sine, triangle or square waveforms, plus it has a sweep function.  Its touchscreen makes for easy and intuitive control in many audio and RF applications.

Specifications
Sine Wave:
1Hz to 10MHz selectable with 1Hz resolution. Accuracy ±50ppm. THD < 0.05% at audio frequencies.
Triangle Wave:
1Hz to 1MHz selectable with 1Hz resolution. Accuracy ±50ppm. Maximum 3V peak-to-peak from 20Hz to 1MHz. Adjustable down to 10mV peak-to-peak.
Square Wave:
1Hz to 1MHz selectable with 1Hz resolution. Accuracy ±50ppm. Fixed 3.3V peak-to-peak from 20Hz to 1MHz.
Sweep:
Sine wave sweep from 1Hz (minimum) to 10MHz (maximum) selectable with 1Hz resolution. Sweep rate selectable between 50mS, 100mS, 200mS, 500mS, 1 second or 2 seconds. Linear sweep or exponential.        Output level from 3V to 10mV peak-to-peak.

Improving your Arduino-based Theremin

In December 2017’s issue we suggested a no-frills Arduino-based digital Theremin. This month we show how you can add a second sensor to the Theremin, which is used to control volume in proper Theremin-style.

Using Cheap Asian Modules – Part 4

Our series based around cheap, imported ready-made modules continues with an idea for measuring temperature and relative humidity using an off-the-shelf AM2302 digital sensor module. Add temperature and RH measurement to your microcontroller projects with ease!  Optional Micromite interface code listing also included.

Teach-In 2018 – Get Testing!
Part 7: Radio frequency measurement and testing

This month, our Teach-In tutors delve into the world of radio frequency measurement techniques including voltage, power, modulation depth and standing wave ratio (SWR). Common examples of RF test equipment are also outlined and a simple project – a wideband RF ‘sniffer’ that detects RF energy is included.

Also in this month’s issue:

• Techno Talk – ‘wet string’ alternatives to fibre broadband!
• PIC ‘n MIX Mike Hibbett ‘picks up’ the reins on our popular for a while, exploring and explaining digital signal processing and the techniques of fast Fourier transform (FFT).
• Circuit Surgery – our expert Ian Bell discusses the principles of low-pass filters, including multiple-feedback filters and the Sallen Key filter. An in-depth primer for electronics constructors, designers and students.
• Audio Out – our column for DIY audiophiles starts a short series on audio filters including a variable Sallen-Key filter and circuit and PCB details for a state variable filter (SVF).
• Net Work About the Spectre and Meltdown CPU bugs recently discovered
• Control System for car air suspension – an interesting (Honda) Insight!

Next month

Micromite BackPack V2; Microbridge PIC32 programmer; High performance 6GHz RF Prescaler; Using low-cost Electronic Modues (Part 5): 16×2 LCDs; Teach-In 2018 (Part 8) – Making digital measurements.