July 2020

Speech Synthesiser with the Raspberry Pi

This simple and straightforward add-on for any current variant (at the time of writing) of the Raspberry Pi can generate a virtually unlimited number of phrases, short or long, streamed as text over a serial port.  It would interface with just about any microcontroller or computer.  Our designer chose the Raspberry Pi Zero as the basis for this unit, and so the project’s DAC/ amplifier board is the same shape and sits directly above it.

A pair of speakers and a microSD card are needed to create a finished working speech synthesiser add-on, along with some means of supplying serial commands to the completed unit, so that it ‘knows’ what to say.  We have also provided some code to allow an Arduino board to control the speech synthesiser. Full constructional details and programming procedures are included in this month’s article.

• Please note that contrary to what it states in the magazine, we are not including the Raspberry Pi OS (was, Raspbian) in this month’s downloads since it is available free from: https://www.raspberrypi.org/downloads/raspberry-pi-os/

Using cheap Asian Electronic Modules:
AD584 Precision Voltage References

We try three low-cost precision voltage reference modules built around the Analog Devices AD584. This reference voltage chip incorporates a laser-trimmed bandgap reference with the ability to set the reference voltage at 2.5, 5, 7.5 or 10V. We check out a few finished products available that can be purchased online and imported from the main Asian sources.

AM/FM/CW Scanning HF/VHF RF Signal Generator (Part 2)

This low-cost easy to build and user-friendly RF signal generator covers from 100kHz to 50MHz and 70-120MHz, and is usable up to 150MHz. It generates CW (unmodulated), AM and FM signals and is suitable for a wide range of tests. Digital LCD display. AD9850-based system using an Atmega 328P microcontroller design. This month, constructional and setup details are provided.

High-current Solid-state 12V battery isolator

This design aims to connect an auxiliary battery to a vehicle’s main battery/ alternator while the engine is running, in order to charge that extra battery. But it disconnects it once the engine shuts down, to prevent the vehicle battery from accidentally discharging. It’s cheap and easy to build and is idea for RVs, campers, offroad vehicles and boats. Solid-state design, rated at 100A or more.

  Good soldering skills are required to complete this design successfully

Audio Out

Part Two of the stylophone-like PE Mini Organ runs through the components list and assembly.

Make It With Micromite (Part 18)
Animated eyes for the Micromite Robot Buggy

This month we add some personality to the robot buggy by adding a pair of animated eyes.

PIC n’ MIX (Part 1: introducing the PIC18 family)

The start of a brand new series that delves into the PIC18 microcontroller family, looking at the devices’ capabilities, software development tools and building up our own development board. We will explore how they can complement the use of the Arduino platform, along with the pros and cons of each. This series is aimed at those already familiar with basic MCU development on platforms like the Arduino, but the key focus is going to be on using the PIC itself.

Part 1 starts with a comparison of PIC family features. A great new series to help PICmicro enthusiasts embrace this family of devices.

Also in this month’s issue:

• Techno Talk – some weird and wonderful devices to create ‘plant-music’ currently being sold online
• Net Work – the Internet column warns about SIM-swapping, reviews popular password managers and a round-up of the latest space program news.
• Circuit Surgery continues the study of D, G and H-class amplifiers and analyses LTspice sources and waveform import/ export.
• Max’s Cool Beans – flashing LEDs and drooling engineers – Max gets to grips with Neopixels.
• Electronic Building Blocks – ideas for modifying solar garden lights.

Next month

Micromite LCD BackPack V3; Steering wheel audio button to infrared adaptor; Junk Mail repeller! Bargain Class-D Stereo + Subwoofer Amplifier modules.  Contents may be subject to change.