INTERVIEW WITH THOMAS SCARBOROUGH

with Andy Collinson of Circuit Exchange International

During the past year, Rev. Thomas Scarborough was the world's most widely
published electronics designer. He has well over 100 designs in print, as
well as many in circulation on the Internet. Andy Collinson of Circuit
Exchange International (http://www.zen22142.zen.co.uk) caught up with him
recently to ask him about his design philosophy, and his personal Top Ten
favourites.

Thomas:

Thanks, Andy. I was pleased to witness the start of your Circuit Exchange
International years ago. It can only be described as an enormous success,
and I'd recommend it to anyone looking for electronic circuits. I think it
took us all by surprise.

Electronics, for me, is not just a technical skill. It is about the elegance
of ideas - even truth. If you can crack the philosophical problem of a
concept, you advance beyond circuitry to revolutionary design. I generally
don't construct designs logically in my mind - at least not consciously.
They appear intuitively, sometimes virtually in toto.

I look for three things in my designs. Firstly, I want to feel that there is
something significantly original about a design. Secondly, I enjoy
minimising a design - paring it down to its conceptual essentials. Someone
once called me Rev. Minimalist. Thirdly, I design deliberately for
longevity. I would like constructors to be able to pick up a design in 10 or
20 years' time, and still be able to repeat it. And perhaps I would add
this - that I like to do designs that people will enjoy.

Here are my ten favourite designs:

1. MATCHLESS METAL LOCATOR.

Silicon Chip magazine (http://www.siliconchip.com.au), June 2002

This design may be downloaded from Geotech - Technology for Treasure Hunting
(http://www.thunting.com)

This was my most popular metal detector design, and was produced in
Australia as a kit. Geotech describe it as the "World's simplest (?) IB
design". The University of Sydney engineering students were challenged to
improve on it, and I think this formed the basis of a new commercial model.
I never understood why, out of more than a dozen of my metal detector
designs, it caught on as it did. At any rate, it was a radical design. It
was an induction balance (i.b.) detector, based on a common 7556 i.c., that
stripped out the usual d.c. amplifier and level detector, creating a metal
detector with good performance with only a dozen or so compoments. But there
has to be a trade-off for such minimalism. In this case it was drift.

2. HIGH VOLTAGE CONJURING TRICK

Circuit Exchange International (http://www.zen22142.zen.co.uk)

This was one of my earlier designs. My late father once was a professional
conjurer, and commented that it was "absolutely brilliant". A conjurer asks
a member of the audience to take four classic shapes - square, circle,
triangle, and rectangle - and to insert all or any or none into a box. They
then close the box, and cover it with a silk. Then the conjurer, by placing
his or her hand on the silk, is able to determine which shapes are inside.
The box and the shapes can be examined closely without revealing the secret
of the trick. The secret was a magnet inside each of the shapes, and a
sequence of high voltage pulses through metal studs on the box, which
revealed its contents. The voltage was so adjusted that this could be felt
only if the conjurer moistened his or her fingers before touching the studs
through the silk.

3. FOREVER FLASHER

Everyday Practical Electronics magazine (http://www.epemag.wimborne.co.uk),
January 2002

This design used a 4016 quad bilateral switch in a decidedly unorthodox way,
pushing it way beyond its specifications, to pulse an l.e.d. literally off
thin air. It was chosen by some students in South Africa as the basis for a
national science competition. They won second prize. With a short aerial and
an earth, using a simple diode pump, the Forever Flasher extracted
sufficient electromagnetic energy from the air to pulse a highly efficient
l.e.d. at 0.5Hz/cps. I built this on a hunch, not seriously expecting it to
work, and was very pleased when it did. I doubt that there is anything else
like it, because it would be hard to find components that would be up to the
task. It is powered by electromagnetic energy from many sources, but
especially nearby mains wiring and applicances.

4. WART ZAPPER

Everyday Practical Electronics magazine, September 2004

This design effectively reduced the power requirements for the removal of
warts to 1/1,000th of what was previously required, thus bringing wart
removal within the scope of the amateur. It proved to be highly effective
for the removal of the common wart. One of my early helpers was a dentist,
who had tried unsuccessfully to remove warts from his hands through standard
methods. The Wart Zapper completely removed them. I stumbled upon the idea
when I experimentally treated a local infection with so-called Crane
frequencies - with the important difference that I directly applied pulsed
d.c. The results were astonishing, and I intuitively applied this to the
removal of warts. The first prototype showed some promise, and more than a
year's experimentation led to the final prototype. At least one embodiment
has now gone into production.

5. POOR MAN'S METAL LOCATOR

Silicon Chip magazine, May 2004

The electronics press widely recognised this as a major new genre, and the
Silicon Chip design was my favourite embodiment of it. This used just two
components, two coils, and a switch and an earpiece, to achieve the
performance of a budget i.b. detector. There was an early challenge to the
originality of the idea on the basis of U.S. Patent 4,196,391 of 1980. But
the patented design used some 60 components, and its purpose was binaural
location using b.f.o., not enhanced sensitivity through mutual induction, as
is the case here. I named the concept beat balance (b.b.). It took advantage
of mutual coupling between two coils to produce a beat frequency. Although
it is not a powerful performer, I doubt that any self-contained metal
detector would deliver more punch per component than this one.

6. CCO METAL DETECTOR

Elektor Electronics magazine (http://www.elektor-electronics.co.uk),
scheduled for publication during 2005

This was another new genre metal detector, based on the transformer coupled
oscillator, or t.c.o. Therefore I named it a coil coupled operation (c.c.o.)
metal detector, of which this embodiment is my personal favourite. It uses
just two components and two coils, and works in conjunction with a m.w.
radio. It has excellent performance - it will pick up an old Victorian penny
at 18cm/7". A t.c.o. essentially consists of an amplifier which, by means of
a transformer, feeds the output back to the input, thus sustaining
oscillation. Unlike an i.b. detector, the Rx section of the c.c.o. detector
is "active" rather than passive, and unlike i.b., a beat frequency
oscillator is required - in this case the m.w. radio.

7. BODY DETECTOR

Everyday Practical Electronics, March 2001

I have designed several sensitive body detectors, which operate on the basis
of picking up the capacitance of the human body. This design was one of the
more convoluted embodiments I produced, but it had the best performance. It
also represented an unusual design approach. It would pick up a human body
at up to half a metre within the normal variations of room temperature.
Besides picking up the human body per se, it has some interesting
applications. It will "energise" almost any metal sensor up to about
20kg/45lbs (e.g. burglar bars, or a bicycle), and will "energise" metal
items (e.g. cutlery on a table) at a distance of tens of centimetres/several
inches. That is, there is no need for a physical connection between the
circuit and the items being protected from human touch.

8. WIND-UP TORCH MK. 2

Everyday Practical Electronics, March 2003

The idea for a battery-less torch was born when I was caught in a
frightening storm in the Pacific, at night, and - you guessed it - my
battery-powered torch failed. This design uses a hand generator and
capacitive storage to provide a reading light for 10 minutes off 20 seconds'
wind, or a "high beam" for about a minute-and-a-half off the same. My first
experiments achieved a mere 3 seconds' light, but through the continual
refinement of techniques, this was extended many times over, and a
serviceable torch was born. Although not nearly as bright as a battery
torch, this served me well when I returned to the Pacific recently. The
design also allows for a significant increase in light intensity with an
attendant loss of duration of light or increase in winding time.

9. THUNDERSTORM MONITOR

Everyday Practical Electronics magazine, November 2004



This was one of my longest-running projects as far as development goes. It
took me well over a year to complete - firstly to "harness" atmospheric
charge, then to monitor and analyse it. However, it provided endless
fascination. For simplicity, it far surpasses other designs of this type, by
matching input impedance with atmospheric charge. Potentially, it will
report the possibility of a lightning strike with just half a dozen common
components. Bearing in mind that lightning causes more deaths than all other
natural hazards except one, and that humans are incapable of detecting the
risk through their five senses alone, this project makes good sense. The
atmosphere is full of unseen activity, and the project also enables one to
monitor variations of atmospheric charge.

10. SUPER MOTION SENSOR

Everyday Practical Electronics magazine, May 2003

This was an exceedingly sensitive passive motion sensor, based on detecting
fluctuations in the level of visible light. It detected a single finger
moving at 5 metres - without the use of a lens. If a suitable sensor and
lens were employed, its range for picking up a moving person might be in the
range of 100 metres. It works by comparing variations in light level over
time, using two sample-and-hold circuits which alternate with one another.
It may potentially be used to detect far slower variations, for instance
irregular warming in a room. This circuit later formed the basis of The
Tracker, which I designed for the premier edition of Servo magazine in the
U.S.A. This used two such sensors to enable a robotic head to track motion.

Runners-up: All-Band Radio, Fluid Finder, World Lamp, Auditory Illusion, and
Jazzy Necklace (this was the original design, which became a disco hit -
sometimes going under the name LED or strobe necklace).