April 2022

This month’s highlights

64 Key MIDI Matrix (Part 1)

This simple to build but powerful project turns an Arduino into a MIDI matrix. These are popular with musicians for triggering samples but commercial ones cost hundreds of pounds. Our project costs just a fraction of that and can be customised by changing the Arduino software. It supports regular or illuminated buttons and can also be programmed to act as a MIDI pass-through, among other roles. Full constructional details are provided.

Digital FX Unit (Part 1)

This digital effects machine creates unique sounds when connected to a variety of instruments, such as an electric guitar, violin or cello, or even the output of a microphone preamp, or within the effects loop of an amplifier or mixer.  The design utilises a digital FX processor chip. There are 15 different effects including chorus, echo, flange, vibrato, wah, reverb and distortion. Each effect has three adjustable parameters. Its heavy duty build is suitable for stage use and its high input impedance will suit piezo pickups. The unit operates from a DC mains adaptor or battery.

Circuitry and construction are described in Part 1 this month, with operating and FX customisation following in Part 2 next month.

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

High-current Battery Balancer (Part 1)

To preserve long battery life, proper balancing of the individual cells will avoid the risk of overcharging some cells while undercharging others. This High-current Battery Balancer does exactly that: it balances two, three or four series-connected cells or batteries and is suitable for Li-ion, LiPo, lead acid and other types. Each cell or battery can range from 2.5V (fully discharged) to 15V, and the project supplies a balancing current up to 2.5A and a charging current up to 50A. It can double as an efficient battery charger or discharger. Circuit principles are discussed in Part 1 and construction will be shown in Part 2 next month.

Audio Out – Analogue Vocoder (Part 6)
Universal Audio PSU

This month a very high quality power supply is offered that is ideal for the Analogue Vocoder described in Audio Out but is also suitable for mixers, synthesisers and other circuits. It also provides a 48V phantom power source. Construction details are provided this month and installation details follow in Part 2.

Flowcode Graphical programming
Part 3: LCD temperature monitor

Expanding Flowcode’s capabilities with a PIC16F88 and RedBoard/ Uno. More applications for the super-easy to use graphical programming environment.

Make it with Micromite (Part 35)
Mini-project: iButton-controlled Electronic Door Lock

Applying a Micromite with colour LCD touchscreen to form the basis of an iButton-controlled door lock.

Also in this issue:

  • Techno Talk – the merits of ecologically ethical electronics
  • The Fox Report – the Right to Repair and more Windows 11 upgrade woes
  • Net Work – hard to find flatbed scanners and drivers, space junk and flying electric taxis
  • Circuit Surgery – a total teardown of the LM35 temperature sensor
  • Max’s Cool Beans Blog – switch bounce demystified, and solid state switches

In next month’s issue:

4-key Arduino MIDI Matrix (Part 2); High-current Battery Balancer (Part 2); Digital FX (Part 2); KickStart Part 8: Introducing the Raspberry Pi Pico. Contents subject to change.

April 2022 files for download - 0422-DL.zip


Printed Circuit Boards

We supply PCBs for all our projects going back to 2013.

New PE service – Programmed PICs

Buy programmed PICs for most of our projects.

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