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ROLL-UP, ROLL-UP!
Ingenuity is our regular round-up of readers' own
circuits. We pay between $16 and $80 for all material
published, depending on length and technical merit.
We're looking for novel applications and circuit tips, not
simply mechanical or electrical ideas. Ideas must be the
reader's own work
and must not have been submitted
for publication elsewhere.
The circuits shown have
NOT been proven by us.
Ingenuity Unlimited
is open to
ALL abilities, but items for consideration in this column
should preferably be typed or word-processed, with a
brief circuit description (between 100 and 500 words
maximum) and full circuit diagram showing all relevant
component values.
Please draw all circuit schematics
as clearly as possible.
Send your circuit ideas to: Alan Winstanley,
Ingenuity Unlimited,
Wimborne Publishing Ltd., Allen
House, East Borough, Wimborne, Dorset BH21 1PF.
They could earn you some real cash
and a prize!
Win a Pico PC-Based Oscilloscope
•
50MSPS Dual Channel Storage
Oscilloscope
•
25MHz Spectrum Analyzer
•
Multimeter
•
Frequency Meter
•
Signal Generator
If you have a novel circuit idea which
would be of use to other readers, then a Pico
Technology PC based oscilloscope could be
yours.
Every six months, Pico Technology will be
awarding an ADC200-50 digital storage oscil-
loscope for the best IU submission. In addi-
tion, two single channel ADC-40s will be pre-
sented to the runners up.
Photo Slave Flash Unit
Flash Pictures
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The use of a second “slave”
flash as the main light enables
the use of creative lighting effects
in flash photography. By placing a
second flash at, say, 45 degrees
to the subject, shadows are
formed to show its texture and
form, and dramatic effects such
as back-lighting, strong side light
etc. are also possible.
The flash on the camera fills
in or softens the shadows made
by the secondary flash. Using the
circuit described in Fig.1, the
camera flash also triggers the
slave flash.
The firing of the camera flash
is detected by the photo diode (or
phototransistor) TR1. Capacitor
C1 blocks the effect of DC
caused by ambient light and
allows only the pulse caused by
firing the camera flash to reach
the amplifier formed by transistor
TR2 and resistors R3 and R4.
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Fig.1. Photo Slave Flash Unit circuit diagram.
The amplified pulse is fed to
the monostable formed by IC1,
R5, C2 and C3. The fixed-
length pulse produced by this is
passed through resistor R6 and
triggers thyristor CSR1. This
shorts the two switch terminals
of the secondary flash, which
then fires.
The circuit works reliably in
ambient light conditions ranging
from full sunlight to a darkened
room, and also responds to
bounced flash. This means that
it is not necessary to point the
sensor at the primary flash,
giving greater scope for
positioning the slave to give the
best lighting effect.
Component choice is not
critical. TR1 has been tested
using a variety of surplus photo-
diodes and photo-transistors
with consistent results. TR2
could be any general purpose
npn
silicon transistor. The circuit
Copyright © 1999 Wimborne Publishing Ltd and
Maxfield & Montrose Interactive Inc
EPE Online, May 1999 - www.epemag.com - 533
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could either be powered from a
6V to 9V battery or from the
flash gun's battery.
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For further ideas, if TR1
were replaced by a microphone
and amplifier, the secondary
flash could be triggered by
sound. This would allow
dramatic photographs of such
subjects as breaking glass.
Similarly, a security camera
could be developed to
photograph burglars if the
output from an intruder alarm
replaced the photo sensor.
Peter Taylor
Mickleover, Derby, UK
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Fig.2. Circuit diagram for a simple Siren Sounder.
Siren Sounder
Take
Heed
A simple alarm circuit,
which is fun to build and will find
many uses, perhaps as a
warning device or as a novelty,
is shown in Fig.2. The alarm is
built around two 555 timers,
which act as oscillators to
produce a distinct two-tone
effect. Note that only one
resistor and capacitor is used on
each oscillator.
Oscillator IC1 runs at a
lower frequency than IC2. The
low frequency signal generated
by IC1 modulates the frequency
of IC2, which changes the audio
tone.
The output from IC2 at pin 3
is fed to the base of
pnp
transistor TR1, which amplifies
the sound and drives the
speaker, LS1. Resistor R4 limits
the collector current.
The frequency and timing of
each oscillator is dependent on
R1 and C1 for IC1, and R3 and
C2 for IC2, and these
components could be changed
to alter the note.
P. Graham
Yate, Bristol, UK
Electronic Rotary Switch
A Good Substitute
In the circuit of Fig.4, a novel
approach has been adopted for
replacing mechanical rotary
switches used in many types of
circuit. A momentary push-to-make
switch together with some
electronics offers an option of
making an electronic rotary switch
to replace a mechanical one.
At power-on, a reset signal is
applied by IC3a/b to reset IC1 and
IC2. The output will be selected
sequentially from Q0 to Q9 of IC2
and the selection will be advanced
every time S1 is closed.
The R-S latch IC1 is used for
switch debouncing and is set high
every time S1 is pressed and reset
after a delay generated by resistor
R1 and capacitor C1. Hence it
provides a debounced pulse, as a
clock input to IC2.
The circuit acts similarly to a
multi-way switch action for which a
4017 counter/divider has been
used. The selection will be
valid until the next switching
action occurs.
When any Q output of IC2 is
selected, it will be at a high state
(logic 1). This can be used to
activate a control pin of IC4 and
turn a corresponding bilateral
switch on. A 4016 Quad Bilateral
Switch is used for this purpose.
At the bilateral switch
output, the user's circuit can be
interfaced as required, so that
this circuit will offer a multi-way
selection to the circuit. This
could be useful in case of the
selection of analog signals
which the 4016 can also handle.
Digital circuits may be
connected directly to the output
of IC2.
A maximum of nine steps'
selection is offered by the 4017.
On every tenth switching, it will
reset itself through IC3b and the
cycle will repeat from Q0
onwards.
To provide fewer selections,
you can select Q outputs of your
choice to reset the circuit. For
instance, if you need only four
selections, then connect Q4 (pin
10) to the OR gate IC3b pin 6
and now on every fifth selection
the circuit will reset and start
from Q0.
B. D. Mehta
Ahmedabad, India
Space Case Alarm
It’s
a Miracle
School pupils often use a
strong plastic “space case” to
house their ruler, pencils, etc.
Copyright © 1999 Wimborne Publishing Ltd and
Maxfield & Montrose Interactive Inc
EPE Online, May 1999 - www.epemag.com - 534
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Fig.4. Circuit diagram for an electronic rotary switch.
My young son wanted me to rig
his space case with an alarm,
so that it would go off when any
other pupil opened the case
without his permission. In the
circuit diagram of Fig.3, lC1 is
an inexpensive CMOS LSI
melody generator, which comes
in different versions (Christmas
Jingles, Happy Birthday, etc.).
When a battery is
connected, ICI plays a melody
once, then stops. While the
sound is not very loud, it is
certainly enough to attract the
attention of a teacher! Switch
S2 is a miniature slide switch
which enables the pupil to set
the alarm and is mounted
inconspicuously in the side of
the case, or even inside.
Microswitch S1 triggers the
alarm when the case is opened.
The battery is a small 3V
lithium manganese cell, which
would probably give a year of
use or more. Leads may be
soldered directly to the battery
but this must be done very
rapidly, taking care to avoid
excess heating. Use anti-static
precautions when handling IC1
with care.
As simple as the design is,
“dad” is delighted to report that
other pupils were offering to pay
my son's dad to construct a
similar alarm for them, too!
Copyright © 1999 Wimborne Publishing Ltd and
Maxfield & Montrose Interactive Inc
Rev. Thos. Scarborough,
Fresnaye, Cape Town, RSA
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Fig.3. Space Case Alarm.
EPE Online, May 1999 - www.epemag.com - 535

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