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WIN HIP

ICRO56DA21

FJ2

C24 LOPME

DEV OARD

OPTO-THEREMIN – PART 1

• Create your own electronic music

• Master eerie Sci-Fi sounds

• Brand new updated design

• Optical proximity sensor controls volume

WIDEBAND, ACTIVE DIFFERENTIAL

OSCILLOSCOPE PROBE

High-performance, low-cost probe with a bandwidth of more than 80MHz

MINI 10W CLASS-D AUDIO AMPLIFIER

Peaking at 91% efficiency, this pint-sized amp delivers an amazing audio punch!

P LU S

PRACTICALLY SPEAKING, CIRCUIT SURGERY,

NET WORK, AUDIO OUT, TECHNO TALK,

HOT BEANS & TEACH-IN 2015

SEPT 2015 £4.40

ISSN 0262 3617



PROJECTS



THEORY



NEWS



COMMENT



POPULAR FEATURES



VOL. 44. No 9

September 2015

INCORPORATING ELECTRONICS TODAY INTERNATIONAL

www.epemag.com

Projects and Circuits

OPTO-THEREMIN – PART 1

by John Clarke

Build your own Theremin – but with an important difference – control the volume

with an optical proximity sensor!

WIDEBAND, ACTIVE DIFFERENTIAL OSCILLOSCOPE PROBE

by Jim Rowe

Here’s a superb design for a high performance, active differential probe – but on

a modest hobbyist’s budget

MINI-D STEREO 10W/CHANNEL CLASS-D AUDIO AMPLIFIER

by Nicholas Vinen

Sometimes the best things come in small packages – here is a mighty amp in

a tiny package that can deliver a whopping 30W!

Series and Features

TECHNO TALK

by Mark Nelson

LED there be light

TEACH-IN 2015 – DISCRETE LINEAR CIRCUIT DESIGN

by Mike and Richard Tooley

Part 8: Power amplifiers

NET WORK

by Alan Winstanley

Chaos theory... Surfing the

EPE

way... For free...

Not forgetting FTP A legacy of projects

...

AUDIO OUT SPECIAL – PRODUCT REVIEW

by Jake Rothman

Review of Peak Analysers

CIRCUIT SURGERY

by Ian Bell

Noise – Part 2: analysis and calculations

Electronic Building

Blocks

By Julian

Edgar

PRACTICALLY SPEAKING

by Robert Penfold

Integrated circuit terminology

AUDIO OUT

by Jake Rothman

RIAA equalisation – Part 3

MAX’S HOT BEANS

by Max The Magnificent

littleBits review

ELECTRONIC BUILDING BLOCKS

by Julian Edgar

Temperature Controller

Regulars and Services

SUBSCRIBE TO

EPE

and save money

EDITORIAL

A little extra for summer... Changes for

PIC n’ Mix

NEWS

– Barry Fox highlights technology’s leading edge

Plus everyday news from the world of electronics

MICROCHIP READER OFFER

Win a Microchip PIC24FJ256DA210 Development Board

CD-ROMS FOR ELECTRONICS

A wide range of CD-ROMs for hobbyists, students and engineers

READOUT –

Matt Pulzer addresses general points arising

drawings, photographs and articles published in

EVERYDAY PRACTICAL ELECTRONICS

is fully

protected, and reproduction or imitations in whole or

in part are expressly forbidden.

EPE

PCB SERVICE

PCBs for

EPE

projects

ADVERTISERS INDEX

NEXT MONTH! –

Highlights of next month’s

EPE

Our October 2015 issue will be published on

Thursday 3 September 2015, see page 80 for details.

Readers’ Services • Editorial and Advertisement Departments

Everyday Practical Electronics, September 2015

E DITORIAL

VOL. 44 No. 09 SEPTEMBER 2015

Editorial Offices:

EVERYDAY PRACTICAL ELECTRONICS

EDITORIAL Wimborne Publishing Ltd., 113 Lynwood

Drive, Merley, Wimborne, Dorset, BH21 1UU

Phone:

01202 880299.

Fax:

01202 843233.

Email:

fay.kearn@wimborne.co.uk

Website:

www.epemag.com

See notes on

Readers’ Technical Enquiries

below

– we regret technical enquiries cannot be answered

over the telephone.

Advertisement Offices:

Everyday Practical Electronics Advertisements

113 Lynwood Drive, Merley, Wimborne, Dorset,

BH21 1UU

Phone:

01202 880299

Fax:

01202 843233

Email:

stewart.kearn@wimborne.co.uk

Editor:

Subscriptions:

General Manager:

Graphic Design:

Editorial/Admin:

Advertising and

Business Manager:

On-line Editor:

Contributing Editor:

Publisher:

A little extra for summer

It’s summer, so – with luck – you have a bit of extra time to read

EPE

the beach, in the garden or wherever you relax. With that in mind we

have pushed the pagination of this month’s issue to 80 pages of electronic

fun, learning and inspiration.

Updating a classic

Our first project this month is an update of a classic, if not

the

classic

electronic instrument – the Theremin. It’s the granddaddy of them all and

today remains the only instrument you play without actually touching it!

EPE

has quite a history of publishing Theremin projects. In previous years,

Jake Rotham, our

Audio Out

columnist produced a pocket Theremin and a

much larger version (you can view some of Jake’s work at:

theremin.co.uk).

However, this new design is by regular contributor John Clarke, who has

updated the traditional design by using an optical proximity sensor. Even if

you don’t intend to build one, it’s a fascinating instrument to read about.

Trivia

My brief foray into the world of pub-quiz-style questions last month did

not exactly result in a tsunami of replies – but we do have a winner! Geoff

Theasby spotted that Ian Bell had secreted a Pink Floyd title in

Circuit

Surgery;

well almost. ‘Careful with that axis’ is near enough the name of

the early Floyd song ‘Careful with that axe, Eugene’. Just to ram home the

point, another heading in the same article was ‘Any colour you like’, also

by Pink Floyd. As promised, Geoff’s prize is… the honour of winning!

Changes for

PIC n’ Mix

Last, but not least, I have some sad news. Mike Hibbett, our tireless,

talented and creative columnist for

PIC n’ Mix

has had to give up writing

for us. In his own words:

Due to some exciting and positive changes to my fulltime work, I find

myself unable to continue writing the

PIC n’ Mix

column. It’s with some

sadness that I put down my pen; I’ve had some great experiences, learned

a lot and made many friends. I will continue to participate in the

Chat

Zone

forum and support Mike O’Keeffe who takes over the role. See you

on the

Chat Zone!

It is typical of Mike’s modesty that he omitted to point out he has been

appointed to a design position in the most prestigious silicon company in

the world. The good news is that he will support and help Mike O’Keeffe

settle into the role of being our new PIC writer.

We wish Mike (Hibbett) the very best for the future, and thank him for all

the wonderful work he has done for

EPE

and the hobbyist community in

the UK and further afield.

MATT PULZER

MARILYN GOLDBERG

FAY KEARN

RYAN HAWKINS

01202 880299

STEWART KEARN

01202 880299

ALAN WINSTANLEY

MIKE HIBBETT

MIKE KENWARD

READERS’ TECHNICAL ENQUIRIES

Email:

fay.kearn@wimborne.co.uk

We are unable to offer any advice on the use, purchase,

repair or modification of commercial equipment or the

incorporation or modification of designs published

in the magazine. We regret that we cannot provide

data or answer queries on articles or projects that are

more than five years’ old. Letters requiring a personal

reply must be accompanied by a stamped self-

addressed envelope or a self-addressed envelope and

international reply coupons. We are not able to answer

technical queries on the phone.

PROJECTS AND CIRCUITS

All reasonable precautions are taken to ensure that

the advice and data given to readers is reliable. We

cannot, however, guarantee it and we cannot accept

legal responsibility for it.

A number of projects and circuits published in

EPE employ voltages that can be lethal. You should

not build, test, modify or renovate any item of mains-

powered equipment unless you fully understand the

safety aspects involved and you use an RCD adaptor.

COMPONENT SUPPLIES

We do not supply electronic components or kits for

building the projects featured, these can be supplied

by advertisers.

We advise readers to check that all parts are still

available before commencing any project in a back-

dated issue.

ADVERTISEMENTS

Although the proprietors and staff of EVERYDAY

PRACTICAL ELECTRONICS take reasonable

precautions to protect the interests of readers by

ensuring as far as practicable that advertisements are

bona fide, the magazine and its publishers cannot give

any undertakings in respect of statements or claims

made by advertisers, whether these advertisements

are printed as part of the magazine, or in inserts.

The Publishers regret that under no circumstances

will the magazine accept liability for non-receipt of

goods ordered, or for late delivery, or for faults in

manufacture.

TRANSMITTERS/BUGS/TELEPHONE

EQUIPMENT

We advise readers that certain items of radio

transmitting and telephone equipment which may

be advertised in our pages cannot be legally used in

the UK. Readers should check the law before buying

any transmitting or telephone equipment, as a fine,

confiscation of equipment and/or imprisonment can

result from illegal use or ownership. The laws vary from

country to country; readers should check local laws.

A roundup of the latest Everyday News

from the world of

electronics

NEWS

Indoors location –

report by Barry Fox

‘I

ndoor location is the last frontier’,

says Erik Bovee, VP Business

Development at Indoors – one of

several companies now learning the

hard way how hard it is to make

satnav systems work without line

of sight to satellites in the sky. But

whoever cracks the problem will hit a

jackpot. Just think how nice it will be

to be guided to the correct departure

gate at a busy airport, navigate a

huge shopping mall or roam a trade

exhibition that spreads over many

halls, often on several levels.

Useful and legal

The challenge is to provide GPS

navigation inside a building, without

contravening laws in Europe and the

US, which prohibit radio transmis-

sion on GPS frequencies. The en-

abling breakthrough was finalisation

of the Bluetooth 4.0 specification five

years ago, with the option of ‘Smart/

Low Energy’ signalling. Bluetooth LE

sends data in bursts rather than the

continuous stream used for conven-

tional Bluetooth. The bursting data

can travel further – between 20 and

70 metres, depending on obstruc-

tions like walls – and the battery in a

beacon lasts at least a year.

Smartphone app and beacons

Broadly, a smartphone app detects

Bluetooth from beacons fixed inside

a building. The beacons transmit

coded fixed-power fingerprint or

identification signals and the smart-

phone detects signal strength (not

angle or time of arrival). Comparing

the relative strengths of several bea-

cons in the immediate vicinity does

the positioning. The position data

works with a stored map to display

progress along a route, with text or

spoken directions.

The beacons can be simple, cost-

ing a few dollars each in bulk, and

give accuracy of around two or three

metres, with a delay of between one

and three seconds before the phone

delivers a location reading. If the

data bursts are more widely spaced;

eg, every 500 milliseconds instead

of every 100 milliseconds, then the

battery can last at least two years.

But wider burst spacing increases

latency, ie, makes location slower.

problem is that exhibitions are only

there for a few days, the maps have

to be prepared and then it’s all over.’

Indoors uses waterproof beacons

the size of a matchbox, made by Pol-

ish company Kontakt.io. So does

another European company Pointr,

which was founded in November

2013 after ‘trying to do indoor navi-

gation for a client who needed it’

and discovering ‘there were no sen-

sible solutions available.’

The original beacon standard was

set by Apple, but there are now

variations on the basic format. Bea-

cons can, for instance, be used for

retail advertising, pulling data about

a shopper from a cloud store and

then pushing individually tailored

sales pitch messages such as ‘Happy

Birthday – we have some special of-

fers for you’, based on spend history

at the store.

Applications

Another application is ‘virtual queu-

ing’. Instead of everyone waiting in

line for counter service, beacons

push a ‘you are next, go to the coun-

ter now’ message to the appropriate

individual – much like the paper

ticket systems used in hospital out-

patient wards.

Beacons could help emergency

services find someone in a crowded

building who has called 999.

Indoors demonstrates a fairly

crude prototype app in their Vienna

labs; the phone displays a simple

floor plan map of rooms inside a

building, with a blue line tracing the

route to be taken and room zones

flashing red when entered.

The trials at San Francisco airport

have already revealed a practical

problem; overloading a blind user

with too much acoustic informa-

tion effectively ‘blinds’ them to au-

dio help.

With support from Cisco, Indoors

is now offering an SDK (software

developers kit) which software de-

signers can use to provide apps

for mapped locations. A test sys-

tem at San Francisco Airport helps

the visually impaired get around

by converting position data into a

headphone description of the sur-

roundings or changing the volume

of an audible prompt depending on

location.

The human problem

It may sound simple but it’s not, says

Erik Bovee. ‘What works for test ro-

bots does not work for humans, who

don’t walk in straight lines and may

go backwards or hold their phone

upside down.

‘The same system could be used to

help visitors navigate large trade ex-

hibitions like CES and IFA. We have

been talking to Reed Exhibitions. The

Everyday Practical Electronics, September 2015

has revealed the final design

he BBCmicro:bit, a groundbreaking,

for the

29-partner collaboration, including

BBC unveils finished BBC micro:bit

85-year hunt may boost

next-gen electronics

ARM, BBC, element14, Microsoft,

Nordic Semiconductor and Samsung.

It will provide a pocket-sized

computer to every year 7 child in the

UK for free. The aim is to to inspire

digital creativity and develop a new

generation of tech pioneers.

The micro:bit is a pocket-sized, co-

deable computer that allows children

to get creative with technology.

In the 1980s, the BBC Micro intro-

duced many children to computing

for the first time. Part of the BBC’s

2015 Make it Digital initiative, the

BBC micro:bit builds on the legacy

of the Micro for the digital age, and

aims to inspire young people to get

creative with digital; develop core

skills in science, technology and en-

gineering; and unleash a new genera-

tion of digital makers and inventors.

It measures 4cm by 5cm, will be

available in a range of colours, and is

designed to be fun and easy to use.

Something simple can be coded in

seconds – like lighting up its LEDs or

displaying a pattern – with no prior

knowledge of computing. All that’s

needed is imagination and creativity.

The BBC micro:bit also connects

to other devices, sensors, kits and

objects, and is a great companion to

Arduino, Galileo, Kano, littleBits and

Raspberry Pi, acting as a spring-board

to more complex learning.

Key features

25 red LEDs

– lights up, flashes mes-

sages and helps users create games.

Final design of the BBC micro:bit, free for

all year 7 UK children

Two programmable buttons

– ac-

tivated when pressed. Use the

micro:bit as a games controller. Pause

or skip songs on a playlist.

Motion detector

– ‘accelerometer’ that

can detect movement and tell other

devices you’re on the go. Featured ac-

tions include shake, tilt and freefall.

Turn the micro:bit into a spirit level.

Light it up when something is moved.

Use it for motion-activated games.

Built-in compass / ‘magnetometer’

–

to sense which direction you’re fac-

ing, your movement in degrees, and

where you are. Includes in-built mag-

net to sense certain types of metal.

Bluetooth Smart Technology

– con-

nect to the Internet and interact with

the world. Connect the micro:bit

to other micro:bits, devices, kits,

phones, tablets, cameras and every-

day objects all around. Share cre-

ations or join forces to create multi-

micro:bit masterpieces. Take a selfie.

Pause a DVD or control your playlist.

Five I/O rings

– connect the micro:bit

to devices or sensors using crocodile

clips or 4mm banana plugs.

n international team led by

Princeton University scientists

has discovered an elusive massless

particle theorised 85 years ago. The

particle could give rise to faster and

more efficient electronics because

of its unusual ability to behave

as matter and antimatter inside a

crystal, according to the research.

The researchers report in the jour-

nal

Science

the first observation of

Weyl fermions, which, if applied to

next-generation electronics, could

allow for a nearly free and efficient

flow of electricity in electronics,

and thus greater power, especially

for computers.

Proposed by the mathematician and

physicist Hermann Weyl in 1929,

Weyl fermions have been long sought

by scientists because they have been

regarded as possible building blocks

of other subatomic particles, and are

even more basic than the ubiquitous,

negative-charge carrying electron

(when electrons are moving inside

a crystal). Their basic nature means

that Weyl fermions could provide

a much more stable and efficient

transport of particles than electrons,

which are the principle particle be-

hind modern electronics.

Want to help at Bletchley?

letchley Park has reported an

explosion in visitor numbers.

A nice problem to have, but they

need more volunteers, in particular

stewards. The role involves helping

visitors to navigate the once-top-

secret site and ensuring it runs

smoothly.

So far this year, more than 100,000

people have already visited Bletchley

Park; an increase of more than 80 per

cent on the previous year. An army

of volunteer staff help each and every

one of those visitors to get the most

out of their day, helping to tell the re-

markable story that lives in the very

walls of this unique heritage site.

The surge in visitor numbers is due

in part to a very special visit a year

ago, by the granddaughter and great-

niece of twins Valerie and Mary

Glassborow, who worked together in

Hut 16 towards the end of World War

Two. The Duchess of Cambridge visit-

ed in June 2014 to formally unveil the

rejuvenated Bletchley Park, following

the £8 million, Heritage Lottery Fund

supported phase one restoration.

Another huge spike in interest fol-

lowed in November, when the Acad-

emy Award-winning film, The Imi-

tation Game, based on the life and

work of Alan Turing and starring

Benedict Cumberbatch and Keira

Knightley, opened in cinemas.

Volunteers at Bletchley Park benefit

from working as part of a great team

and have access to extensive resourc-

es and libraries. Full induction and

training is provided. Other roles are

also available in Education and Es-

tates. To find out more, please email

volunteer@bletchleypark.org.uk

call 01908 640404.

n alliance led by IBM Research

has announced that it has

produced

the

semiconductor

industry’s first 7nm node test chips

with functioning transistors. The

breakthrough could result in the

ability to place more than 20 billion

tiny switches (transistors) on a single

fingernail-sized chip.

To achieve the higher performance,

lower power and scaling benefits

promised by 7nm technology, re-

searchers had to bypass conventional

semiconductor manufacturing ap-

proaches. Among the novel processes

and techniques pioneered by the IBM

Research alliance were a number of

industry-first innovations, most nota-

bly silicon-germanium (SiGe) chan-

nel transistors and Extreme Ultravio-

let (EUV) lithography integration at

multiple levels.

IBM reaches 7nm

Everyday Practical Electronics, September 2015

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