February 2020

Audio DSP (Part 2)

This versatile project is difficult to ‘pigeon-hole’. It’s a digital signal processor, an active crossover, a parametric equaliser and more, all in one. It’s based on a powerful 32-bit PIC processor and high quality ADC and DAC converters. The circuit uses DSP to provide an 8-channel parametric equaliser so you can adjust frequency response to exactly the way you want it with really low distortion and noise. Or use it to ‘bi-amplify’ a pair of speakers or simply experiment with any audio signal. It has a future-friendly modular expansion capability. Features a 128×64 graphical LCD and menu-driven interface. Software written in Microchip C.

In Part Two this month, we finish describing the circuit and present the parts list and board assembly instructions.

USB Keyboard and Mouse Adaptor for Micros

This small adaptor makes it easy to connect a USB keyboard or mouse to any micro project such as an Arduino or Micromite. It translates mouse or keyboard clicks into serial data and needs only one pin on a micro to receive it. Discrete PTH circuit board design.

Using Cheap Asian Electronic Modules (Pt. 21)
Stamp-sized digital audio player

The ‘DFPlayer Mini’ is a low cost digital audio player module available from most popular online tech and gadget suppliers.

Measuring just 21mm square, it has a 24-bit stereo DAC, built in 2W mono amp and plays MP3, wma and wav files on a microSD or USB flash drive. This month we strip down the hardware and examine ways to drive the module, including using an Arduino.

Colour Maximite Computer (Part 4)

We continue exploring features of this funky retro-80s style home computer with graphics demos, demo programs and hardware control.

Audio Out – Introducing the PE Mini-monitor crossover for Wavecor drivers (Part 1).

The quest continues to create from scratch a perfect (or as near as possible) mini monitor loudspeaker that emulates the performance of the famous LS3/5A. Our expert has selected drivers from the Chinese manufacturer Wavecor, offering excellent performance and the likelihood of good lines of supply. An absolute must-read for audiophiles everywhere.

Make it with Micromite (Part 13)

We continue exploring the capabilities of this excellent PIC-powered BASIC microcontroller  by utilising ‘bit banging’ techniques to drive an RGB LED and create a mood light.

Motion-Triggered 12V Switch

This simple transistor project switches on a 12V circuit whenever acceleration or vibration is detected.  Originally designed for in-car operation of a dashcam from an always-on accessory circuit, it’s sure to find other uses.

Also in this issue:

• The Fox Report – Barry Fox tries Nero’s Burning ROM again, with mixed results
• Techno Talk – the latest developments in near-transparent batteries and ‘croissant capacitors’
• Net Work – news of our new web site  and latest online trends
• Circuit Surgery – a bumper column this month, continuing with an in-depth explanation of logic levels
• Practically Speaking – some ideas for a PCB digital microscope are explored
• Using Stepper Motors (Part 5) – our  series finishes off by looking at some commercially available stepper motor drivers
• Max’s Cool Beans – introducing Richard Grafton, who’s very active on the UK ‘maker’ scene
• Electronic Building Blocks – repurposing an old camera battery

Next month

Audio DSP (Part 3); Multi-diode Curve Plotter; Galvanic Skin Response; Steam Train Whistle; Bluetooth-Micromite operation. Contents may be subject to change.