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Articles in this series:
|
An alarm-triggered
security c3lllera
Have you been through the trauma of
having your house burgled? This device
will capture the thief's action on film
using a low-cost motor-drive camera.
By TONY NIXON
There have been numerous designs
for burglar alarms presented over the
years but never one to record a thief
in action. It's a simple security camera system that's designed to photograph a thief in action. It's similar in
concept to the security cameras used
in many banks and building societies,
32
SILICON CHIP
except that this unit takes photographic stills.
Imagine a family that has just returned home from an outing only to
find that someone had robbed them of
their valuables. After the initial shock
they check the alarm and, yes, it had
gone off only to be ignored by neigh-
hours as a false alarm. Obviously, the
burglar had quickly taken all he could
and fled the scene with no-one the
wiser.
A subsequent call to the local police station reveals that they know of
a burglar operating in the vicinity but
they don't know who the person is.
"We'll get the offender sooner or later
but we don't have any clues at the
moment", is the reply. So the family
sits down, feeling somewhat helpless
by it all.
Hang on a minute - the camera!
A quick scurry to its hiding place
reveals that , yes, it has taken a few
shots . Within a few hours, the film
has been processed and there 's the
◄
Left: the author, caught in the act of
"nicking" his own VCR. Provided it's
properly set up, the hidden security
camera should be able to provide
positive identification of a thief
should the need ever arise.
burglar in all his glory, lifting up the
video player. From that point on, it
should be relatively easy for the police to identify the burglar and put an
end to his activities.
The point is that if it can work for
the banks, it can also work at home.
The project described here can accomplish this at a fraction of the cost
of commercial units. It uses a passive
infrared (PIR) sensor, a low-cost motor-drive camera, and a small electric
motor and gearbox. It's easy to build
·using "off-the-shelf" components and
the mechanical work is quite straightforward.
The installation is also straightforward and the unit can be used on its
own or integrated with an existing
burglar alarm system. In the latter case,
the unit is armed only when the main
burglar alarm has been triggered and
ceases to- operate when the alarm has
timed out.
In addition, you can either switch
the unit to take a single photograph
each time it senses movement or to
take a complete sequence of photographs at preset intervals (AUTO
mode).
How it works
The circuit may appear complicated
at first glance but can be broken down
into .sections. Fig.1 shows the circuit
details.
When power is first applied to the
circuit, presettable up/down counter
ICl (4029) is reset by a high pulse
from Cl. This high is inverted by IC3f,
the output of which then resets the
latch formed by IC2a & IC2b. It also
resets 556 timer circuits IC4a & IC4b.
At the same time, pin 13 of IC2d is
pulled low via D11, which means that
pin 11 of IC2d is high.
When ICl resets, its internal counter is preloaded with a value that corresponds to the logic states on its
J1-J4 JAM inputs, as set by switches
SW1-SW4. This sets the number of
"shots" that can be taken by the cir-
The Alarm Security Camera is connected to the main alarm system & is armed
only when the alarm is triggered. The camera is then activated when a passive
infrared sensor detects movement. Alternatively, the unit can be used by itself
& armed using a hidden switch near the front door.
cuit. Since the maximum possible ·
count is 15, a 12-shot film should be
used and the film counter set to 12.
This film count can be changed at
any time by altering the switches and
then momentarily operating reset
switch SW5. If switches SW1-SW4
are all left open, then the maximum
film count will be set. SWl sets the
most significant bit (MSB). As long as
this count is not zero, the circuit is
enabled.
Arming options
The circuit is armed when pin 9 of
IC3d is pulled low via optocoupler
IC5. This optocoupler is in turn controlled by a relay in the central alarm
system.
Normally, the "Y" terminal is connected to ground in the central alarm
system and the "X" terminal switched
to +12V by the external relay when
the alarm triggers. This then turns on
the transistor inside the optocoupler
to arm the camera circuit. In this way,
no photos can be taken during exit
and or entry periods, or if the alarm
times out.
Alternatively, if the alarm relay
switches to ground, the "X" terminal
should be connected to the +12V supply rail in the alarm and the "Y" terminal connected to the relay contacts.
When movement is detected, the
PIR sensor's normally open (SNO) contacts close and IC3e's pin 10 output
switches high. R14 and C4 prevent
any glitches from false triggering the
circuit. The resulting low from IC3a is
then inverted by IC3b and turns on
Ql and relay RL1 for the same duration as the relay in the PIR sensor.
RLl thus operates as a slave relay
for the sensor and its contacts can be
used to trigger the main alarm panel.
This means that the P IR sensor can
function as an alarm sensor in addition to its role as a trigger for the
security camera.
When the alarm triggers, pin 9 of
IC3d is pulled low and R7 pulls pin
13 of IC2d high. If SW7 is open, no
further action takes place. If, on the
other hand, SW7 (ACTIVATE) is
closed, the high from IC3b pulls pin
12 of IC2d high via D3. IC2d's output
thus switches low and the resulting
MARCH
1993
33
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SILICON CHIP
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Fig.1 (left): the circuit is armed when
pin 9 of IC3d is pulled low via
optocoupler IC5. When the IR sensor
detects movement, pin 11 of IC2d
switches low & resets monostables
IC4a & IC4b via C2 & D2. IC4a sets the
delay between consecutive photos,
while IC4b generates the starting
pulse for the motor.
negative-going pulse from C2 sets the
latch formed by ICZa & ICZb. This
switches pin 3 of IC2a high and lights
LED 2 to indicate that the unit has
triggered.
In addition, the negative-going
pulse from CZ triggers monostables
IC4a & IC4b. These two monostables
are part of a 556 dual timer IC and
work in the same way as the morefamiliar 555 timer IC. When triggered,
their outputs at pins 5 and 9 switch
high.
IC4a sets the delay between con secutive photographs. When its output switches high, C7 charges via Rl 7
and, after a short delay, pulls IC3c's
input (pin 5) high also. The resulting
low output from IC3c then pulls pin
13 ofIC2d low, thus forcing its output
high for the duration of IC4a's delay.
Any further sensor pulses are now
ignored until this delay is over.
The high from IC4a also clocks !Cl
to reduce the film count by one. When
this count reaches zero, pin 7 (carry
out) of !Cl goes low and pulls pin 13
of IC2d low via Dl to disable the
circuit. This also extinguishes LED 1
to indicate that the film has run out
and to indicate that no further photos
can be taken until the circuit is reset.
IC4b is also wired as a monostable
but has a much shorter delay than
IC4a. Its function is to start the motor
via D9, R18 and Q2 . Once the motor is
running, it closes microswitch S9 via
a motor-driven cam. This ensures that
the motor completes one full revolution only, so that only one photograph
is take!]. each time the system is triggered. When the motor has completed
one revelution, the microswitch opens
again and the motor stops.
IC4a now times out and its output
at pin 5 switches low again and reenables IC2d via IC3c and D7. Any
further input pulses from the sensor
will now retrigger the circuit, provided ICl 's counter is not at zero.
Thus, each time the IR sensor detects
+12V 0 - - - 1 - - . . - - - 1
+
01
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100 +
25VW+
GND
t------•8V
10 +
.,. 16VW+
Fig.2(a}: this circuit can be used to generate
an +8V supply rail for the camera circuit if
this rail is not already present in your central
alarm system.
r----------------•12V
t12V FROM
PLUG-PACK
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BATTERY T
BACK-UP I
12V 1.2AH
.l_
l
IGO
Fig.2(b): use this circuit to generate the required
+12V & +8V supply rails if the security camera is to
be used independently of an alarm system.
movement, the camera takes another
photo.
VRl sets the delay for IC4a and
thus sets the delay between photographs. The maxi_m um setting is about
60 seconds. VRZ controls the length
of the motor start pulse from IC4b.
Auto function
Switch SW8 controls the AUTO
function. If SW8 is closed, a high logic
level will remain on pin 12 of IC2d
after the first photograph has been
taken. Thus, as soon as IC4a times
out, pin 13 of ICZd will go high again
and retrigger IC4a & IC4b to take a
second photograph. This sequence
will continue until the counter reaches
zero.
As a result, the camera will take a
complete sequence of photos, the interval between each photo depending
on the setting of VRl.
Cut wire sensor
Pin 9 of IC2c is normally held low
by a link which connects the CUT
terminal to ground at the sensor. If the
sensor wires are cut to try to defeat
the system, pin 9 of IC2c is pulled
high by R16 and its pin 10 output
switches low. This in turn pulls pin
11 ofIC3e low via DlO and thus turns
Ql on to trigger the alarm. The camera circuit now goes into AUTO mode
and takes a sequence of photos until
the film counter (ICl) reaches zero.
SW6 functions as the TEST switch.
When this switch is closed, it pulls
pin 9 of IC3d low and this enables the
camera circuit so that its various functions can be tested independently of
the central alarm system. If, at any
time, the photographic option is not
required, it can be disabled by opening SW7. The alarm system will still
trigger via the slave relay (RL1) however, either due to the sensor detecting movement or the wires being cut.
Note that if the alarm times out,
then the camera circuit will be disabled even if there is still film available.
Power supply
Power for the circuit is derived from
+12V and +8V rails in the main alarm
system. Fig.Z(a) shows how a suit.able
+8V rail may be derived using a 3terminal regulator if this rail is not
already present. Fig.Z(b) shows a suitable power supply for the circuit if it
is to be used without an alarm system.
The motor is operated by a separate
3V battery which connects via switching transistor QZ. This method was
used because the start-up current of
the motor is quite high and this may
cause difficulties with some alarm
PARTS LIST
1 PC board, code 03103931,
140 X 85
1 PC board, code 03103932,
105 X 57
1 motor drive camera (eg,
Hanimex 35HL)
1 plastic jiffy box, 196 x 113 x
60mm
1 self-adhesive front-panel label,
186 X 100
1 motor-gearbox kit (Jaycar· Cat.
YG-2712)
1 8-way SPST OIL switch (SW1SW8)
1 microswitch (S9) ·
1 12V SPOT relay
8 2-way PC-mount screw
terminal blocks
1 2 x AA square battery holder
1 1MQ trimpot (VR1)
1 100kQ trim pot (VR2)
1 75mm length of aluminium
angle (25 x 25 x 3mm)
1 piece of aluminium sheet, 30 x
87 x 1mm
6 plastic cable ties
1 passive infrared sensor
Semiconductors
1 4029 presettable up/down
counter (IC1)
1 4011 quad NANO gate (IC2)
1 74C14 hex Schmitt trigger
(IC3)
1 556 dual timer (IC4)
1 4N25 optocoupler (IC5)
1 BC548 NPN transistor (01)
1 BO649 Darlington transistor
(02)
10 1N914 silicon diodes (01-03,
05-011)
1 1N4002 silicon diode (04)
2 5mm green LEDs (LED1,
LED3)
1 5mm red LED (LED2)
Capacitors
1 100µF 25VW PC electrolytic
1 47µF 25V PC electrolytic
1 22µF 25V PC electrolytic
2 2.2µF 16VW PC electrolytic
1 1µF 16V PC electrolytic
3 0. fµF metallised polyester
2 .01µF metallised polyester
Resistors (0.25W, 5%)
14100kn·
210kQ
1 3.3kQ
31.5kQ
MARCH
1993
35
Fig.3: here are the wiring
details for the two PC
boards & the passive
infrared sensor (PIR). Take
care with the orientation of
the ICs when installing
them on the main board &
note that Q2 is installed
with its metal face towards
the relay (RL1). SWl-8 is
the DIL switch & its settings
are shown in the table
below.
PASSIVE INFRARED SENSOR
-
+12V NC COM NO
1
n1=1
GND +12V
CUT SNO
TO MAIN PCB
DIL SWITCH SETTINGS
Switch Function
systems, particularly those with
"power fail" detection. These batteries should last a couple of years and
can also be used to power the camera.
Finally, the circuit should not affect the operation of the back-up battery in the main alarm system since
its standby current is only about
25mA. This rises to about 80mA when
the relay and LEDs are on.
Assembly
Most of the parts are mounted on a
main PC board coded 03103931. A
second PC board (coded 03103932)
provides interfacing for the motor and
microswitch (S9). Fig.3 shows the wiring details.
Comments
SWl
Film Set Open for logic 1 (MSB)
SW2
Film Set Open for logic 1
SW3
Film Set Open for logic 1
SW4
Film set
SW5
Reset
Normally open. Resets film counter.
SW6
Test
Normally open. Close for testing.
SW7
Activate
Norma lly closed. Open to disable
circuit.
swa
Auto
Close for full sequence of shots at
first triggering .
Begin construction of the main
board by installing the wire links, then
install the resistors diodes, transistors, capacitors and ICs. IC sockets
were used on the prototype but these
can be considered optional. Be sure to
install Q2 as shown, with its metal
tab towards the centre of the board.
Once these parts are in, the larger
components can be installed on the
board. These include the relay, the
miniature DIL switch (SW1-SW8) and
the two PC-mounting insulated screw
terminal blocks.
Fig.4 shows the dimensions of the
mechanical parts. After the parts have
been made, remove any burrs on them
and make sure that the plunger fits
Open for logic 1 (LSB)
easily into its support bracket.
The mechanism is designed around
a motor-gearbox kit from Jaycar Electronics and a Hanimex 35HL motordrive camera. The motor sells for
around $20.00 and the camera for
about $50.00.
All of the parts, apart from the main
PC board, fit into a large plastic case
as shown in the photos. The three
aluminium brackets and the gearbox
mounting holes can be used as templates for drilling mounting holes. You
will also have to drill a large hole in
the case directly in front of the camera lens.
.The 0. lµF capacitor can now be
soldered directly to the motor terminals, along with two flying leads
which can later be connected to the
interface board. This done, the brackets and motor-gearbox assembly can
RESISTOR COLOUR CODES
D
D
D
D
D
36
Value
4-Band Code (1%)
5-Band Code (1%)
2
100kQ
10kQ
1
3
3.3k0
1.5k0
brown black yellow brown
brown black orange brown
orange orange red brown
brown green red brown
brown black black orange brown
brown black black red brown
orange orange black brown brown
brown green black brown brown
No .
14
SILICON CHIP
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MATERIAL: 25 x 25 x 3 ANGLE ALUMINIUM
25
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MATERIAL: 25 x 25 x 3 ANGLE ALUMINIUM
SHAFT SUPPORT BRACKET
MATERIAL: 25 x 25 x 3 ANGLE ALUMINIUM
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MATERIAL: 1.6 ALUMINIUM
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DIMENSIONS IN MILLIMETRES
DRIVE SHAFT
Fig.4: this diagram shows the dimensions of the three metal brackets, the plunger & the motor
drive shaft. These parts may have to be varied to suit different cameras.
be secured inside the case using machine screws and nuts. Note that the
two mounting screws for the plunger
bracket will have to be countersunk
to clear the plunger.
The dimensions shown for the motor drive shaft are for the Hanimex
35HL camera. If a different camera is
used, then this distance may need to
be altered.
The microswitch is attached to the
motor board using two screws and its
normally closed contacts (ie, the two
outer contacts) wired to the terminal
block. If necessary, the microswitch
can be adjusted by filing a slot in the
PC board at the top mounting position.
The motor board can now be slid
partly into the case using the second
set of guides and the leads from the
motor connected. This done, the board
can be pushed right down into the
case so that the microswitch arm sits
between the switch body and the motor shaft (see photo) .
Don't install the wiring between
the motor board and the main board
at this stage - that step comes later.
Testing
To test the motor and plunger assembly, go to the interface board and
MARCH
1993
37
The PC board was mounted on the back of the case but there's no reason why it
cannot be housed in the case used for the alarm system if there's sufficient
room. The IR sensor can also be mounted separately from the camera.
temporarily connect the "+8V" terminal to the "M" terminal and connect
the "H" terminal to the "GND" terminal. This done, connect the batteries.
If the microswitch contacts are closed
when the battery is connected, the
motor will operate until the contacts
open again (ie, when the motor shaft
presses the actuating arm down).
When the motor stops, momentarily short the "GND" terminal to the
"M" terminal and check that the motor starts again and completes one
revolution. If the motor continues to
operate, adjust the position of the
microswitch so that the motor stops
when the actuating arm is pushed
down by the motor shaft.
At this point, the shutter plunger
should be in its normally up position.
When everything is working OK, remove the batteries °from their holder.
The motor board can now be connected to the main board so that the
entire assembly can be tested (do not
connect the infrared sensor or install
the camera at this stage). VR1 and
VRZ should initially' be set to mid-
The large cutout in the motor interface board is used to
provide clearance for the motor. Don't forget to solder a
0.1µF capacitor directly across the motor terminals.
38
SILICON CHIP
position and a jumper wire temporarily connected between the CUT terminal (middle of the board) and the
GND terminal (top of the board). The
"X" and "Y" terminals should be left
disconnected and all of the switches
should be left open except for SW6
(TEST) which should be closed.
When the switches have been correctly set, reconnect the batteries and
apply power to the main board. LED 1
and LED 2 should immediately light
to indicate that the power is on and
that film is available. Check that the
slave relay operates if the SNO terminal is momentarily shorted to ground.
The main board can now be tested
for correct operation by closing SW7
(ACTIVATE) and momentarily shorting
SNO to ground again. If all is correct,
the slave relay will operate as before,
LED 2 will light to indicate that the
circuit has triggered, and the motor
will start and complete one revolution.
If the motor now keeps going or if it
just starts and then quickly stops , adjust VRZ until it operates correctly.
When the adjustments are correct and
the motor stops turning, no further
action should take place until IC4a
times out, even if SNO is shorted to
ground again. After IC4a times out,
the sequence can be repeated.
Now check that LED 2 goes out if
the RESET switch (SW5) is closed. If
it does, open SW5 again, close the
AUTO switch (SW8) and momentarily short SNO to ground again. The
motor should now start and stop as
before and LED 2 should come on
again. As soon as IC4a's delay ex-
This close-up view of the motor-gearbox assembly shows
how the motor shaft normally holds the microswitch arm
depressed to keep its normally closed (NC) contacts open.
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additional delivery cha rge
applies if the c harger/s is/are
bought.with the above three
battery oiler.
These are new 16 character
by 2 line alphanumeric LCD
display modu les, with surface
mount control ci rcuitry
mounted on the rear of the
display. Requ ire a few
milliamperes at SV to operate,
information included:
Based on a brand new . very
compact modern EHT llyback
transformer which includes an
EHT diode rectifie r. We
supply the transformer, a very
simple circuit, and the
components to suit . All you
need to make a very simple
EHT, DC or pulsed AC
supply. Powered from 12V
DC supply. G reat for EHT
experiments , EHT testing,
pla sma displays, etc . Total
price for the transformer and
the components is ONLY ;
,
These industrial qua lity
detectors wil l detect ferrous
and non-ferrou s metals at
close pro ximity . Some are DC
powered (10-30V0, some are
AC powered (Mains) . and all
w ill switch loads directly. All
have a three wi re for co nnect·
ing in to ci rcuitry: Two fo r th e
supply, and one for switc hing
the load. LIMITED
QUANTITIES at a small
fraction of their real price :
PRICE?
EHT GENERATOR
KIT 'I
LED DISPLAYS
A high quality laser beam
diverging (bea m ex pander)
glass lens. mounted on an
aluminium plate. with
mounting screws provided
Dimensions : 25 x 25 x 6mm
Use it to expand the laser
beam tor Holography. Special
Effects. or one of the two
lenses requ ired to fine focus a
laser beam . for Surveying and
Bar Code Reading.
.
$79
(Item No. 0166)
Note that an LSI surtace
mount controller IC for this
display is available. This IC
has a built in ch aracte r set
generator and many other
features . It is compatible with
8080 and 6800 MPU's. The
IC is available elsewhere for
about $35 , and we will supply
more information upon
request .
IR LASERS
SPECIAL
Brand new large 640 x 200
dot matrix LCD displays ,
made by EPSON - SEIKO,
screen size is 120 x 265m m ,
has built in drivers. Four bit
TTL intertace , a total of 14
connections are requ ired for
signal and powe r (+5V, - 12V).
Capable of displaying
characters , graphs, patterns
etc. 28 pages of information
included. ON SPECIAL Jar
Brand new industria l grad e
PANASON IC 12V/6.5AH
sea led gel batteries at a
reduced price . Yes 6.5
AMP ERE HOURS! Use them
in lighting , alarm s.
commu nications. laser power
suppli es. so lar systems etc .
Dimensions: 100 x 94 x
65mm. Weight o f one battery
is 2.2KG! The SPECIAL
--- ~"<':"'"#'·::
•"' "" ;'_L_, r,..,·
"°J""'•j,;·i
~-~,~---~ ~-. _)
~~ -
,
1wo used 3mW Siemens HeNe visible red laser tubes,
and one of our efficient 12V
universal laser supply kits.
$109
Item No. 00105X
$18
5
$80
ea. or
for
(Ite m No. 0131)
MASTHEAD
AMPLIFIER KIT
Based on an IC with 20dB of
gai~. a bandwidth of 2Ghz
and a noise figu re of 2,Bdb
this amplifier kit out performs
many other IC's , and is a
fraction of their cost. The
complete kit of parts for the
masthead amplifier PCB and
components, and the power
and signal combiner PCB and
components, is priced at an
incredible :
$18
Fore more info rmation see a
novel, extremely popular, and
an ·effective active antenna
design which employs this
amplifier: MIRACLE T V
ANT ENNA - E.A. May·-1992.
TUNING FORK
in
--
SIX DIFFERENT MOTORS
FOR A TOTAL COST OF
$30.
ULTRASONIC
BURGLAR ALARM
KIT
···• •
·. ··
.
'! , ' ' ., .
.
.
Each one of these ide ntical
PCB filter assemblies
contains six three terminal
tuning fork l ifters (IN•GNDOUT), at different frequencies
in the audio range: 1.8·3 .1
Khz.
These high quamy dual fork
filters have very narrow
bandwtdths , and could be
use d as the basis of a
selective call system , high
stability osci llators etc.
$20a pair,
Sma ll PCB Assembly based
on a ULN22321C.
This device has a bu ilt in light
detector , fil ters, timer, narrow
angle lens, and eve n a siren
driver circuit that can drive an
external speaker. Will detect
humans crossing a narrow
corridor at distances up to 3
metres. Much higher range s
are possible if the detector is
illum inated by a remote
visible or IA light source . Can
be used at very low light
levels . and even in total
darkness. W ith IR LED . Full
information provided . The IC
only . is \-.\.irth $16! OUR
PRICE FOR THE
AS~~BLYIS :
;Jib EA. OR 5 FOR $25
Item No. 0163
D.C. MOTORS
· We have good stocks of 5
different high quality
JAPAN ESE DC Motors.
These should suit many
industrial, hobby, robotics and
other applications . Check out
the SPECIAL prlces, and
com pa re!
M1 • 24V, I No load = 50mA ·
22 ,000 RP M at 24V, main
body 28mm Diam - 40mm
long ... $5.50
M4 • 3-15V, I No load, 20 mA
at 12V, main body 3 1mm
Diam · 22mm long ... $ 3
M5-3-15V, I No load • 60mA ·
5700 RPM at 12V, main body
28mm Diam • 40mm
long ... $2.50
M9-12V, I No load= 0.52A ·
15,800 RPM at 12V, ma in
body 36mm Diam • 67mm
long ... $8.50
M 14 • Made for slot cars. 48V, I No load = 0.84A at 6V,
at max efficiency 1,,. 5.7A.
7500 RPM, main body 30mm
Diam - 57mm long ... $9.50
Further to the above special
prices, during Feb.-March we
are offering an introductory
package w hich includes O NE
O F EACH O F TH E ABOV E
MOTORS, and one of the
STEPPER MOTORS
advertised elsewhere in this
ad . (Item No. 0 140) .
PROJECTION
LENS
.a
See S.C. May 88 for this high
quality crystal locked
ultraso nic design. Ca n be
used as a detector or a self
standing alarm , has provision
for bonnet/boot protection and
flashing light and back up
battery . Easily combined with
ou r U.H. F. Remote Control.
CL EARANC E PRICED AT
ONLY:
$29.90
(Cat. No. GK125)
For the P.C. B. and all parts,
except the screw term in als.
A pair of ultrasonic
transducers is included!!
DON'T MISS OUTI
ELECTRONIC KEY
KIT
=·-
~
Main body has a diameter of
117mm and is 107mm long.
The whole assembly can be
easily unscrewed to obta in
three very large lenses : two
plastic and one glass. The
basis of the cheapest large
magnifier or projection
sy$1em? Experimenters
delight at
ON LY$28
-
"~'~.,.~.~~
strikers for entering buildings,
car alarms , central locking ,
the most secure key ever
(See E.A. July 92): ON
$49.90
SPECIAL<at>
For two keys, and one
decoder kit. Cat. No. GK138 .
!afl~f~!~!s~~~•cs
I/
f:-Telephone : (02) 579 4985 Fax : (02) 570 791 0
1..i •
MELBOURNE AGENT TRUSCOTT S (03 ) 723 3860
..... MAJOR CARDS ACC EPT ED WITH PHONE ,. .
FAX ORDERS . P+P
.
~:~.''!'· . . •
i,,.,,£,Q.R MOST MI XED ORDERS : AU STRALIA : $6. N .Z . !Air Mail) : $ 10
:-c. • ,-.·~
Each time the motor starts, the motor drive shaft operates the plunger,
the camera shutter trips & the camera automatically "winds on" to
the .next frame. The motor drive shaft also releases the microswitch
arm to ensure that_the motor completes one full revolution.
pires, this cycle should repeat automatically and continue to do so until
the film counter reaches zero. At this
point, LED 1 (FILM) should extinguish
and the motor should stop permanently.
If all is well so far, reset the system
again (by closing and opening SW5),
open SW8, and remove the link fitted
between the CUT terminal and GND
(this simulates the sensor wire being
cut). The slave relay should now come
on and stay on, while the motor should
operate repeatedly until the film counter reaches zero.
Finally, the camera can be installed
in the case and tested for correct operation. There should be a small clearance between the bottom of the
plunger and the camera button, otherwise the button may not fully release.
If this happens, the film will not automatically wind on.
Note that the base of the camera
may need a bit of packing under it to
wedge it into the correct position.
40
SILICON CHIP
Don't forget to open SW6
(TEST) when the above test
procedure has been completed.
. ALARM
REL~Y
CONTACTS
+t2V
1
IC5
4N25
ALARM
SYSTEM
Installation
On the prototype, the
main board was mounted
on standoffs on the outside
of the lid and secured using
screws and nuts. Alterna-·
tively, it could be mounted
in a separate case or, if there
is sufficient room, inside the
case used for the central
alarm system.
Obviously, the camera
must be installed in a location so that it doesn't stand
out. Some houses are fitted
with removable vents in the
walls near the roof. This
makes an ideal spot in
which to hide the camera,
although you will need to
cut a neat hole in the vent
X
.....,_-------0-----,
y
DV
R20
3.3k
(a)
X
+t2V
IC5
t 4N25
ALARM
SYSTEM
Y
R20
3.3k
ALARM
RELAY
CONTACTS
DV
(b)
Fig.5: the alarm s_e curity camera is armed
using a relay in the main alarm system.
Connect the X & Y inputs as shown in (a) if
this relay switches to +12V & connect them as
shown in (b) ifit switches to OV.
so that the camera lens can "see" the
room.
Another approach would be to fit
the unit into a strong steel box and
use "Bandit" glass over the lens opening. This could then be mounted up
high in a garage or workshop.
When the camera unit is in position, the various connections can be
run to the central alarm system. These
include the power supply connections, the "X" and "Y" terminal connections, and the (optional) slave relay contact connections. Fig.5(a)
shows how to wire the "X" and "Y"
terminals if the external alarm relay
switches to +12V, while Fig.5(b) shows
how to wire the terminals if the external relay switches to ground (GND).
The infrared sensor can either be
mounted on the camera box or installed separately. It should be wired
to the main board as shown in Fig.3.
Satellite siren
Because the camera generates some
noise while it is operating, a small
piezo siren should be mounted inside
the room. This siren should be wired
to sound at the same time as the main
alarm siren and will mask any sounds
from the camera. As a bonus, it will
also annoy the intruder with its piercing sound and hopefully encourage
him to leave quickly.
· The flash on the camera should be
turned off to ensure good battery life.
This means that the system as described will only work satisfactorily
during daylight hours or if the lights
are on. It cannot produce useful results if the room is in darkness.
Note that, for normal operation,
switch SW7 (ACTIVATE) -is closed
while switch SW6 (TEST) is left open.
SW8 should be closed for AUTO operation, while switches SW1-SW4
should initially be set to suit the
number of shots on the film. For 12
shots, leave SW1 and SW2 open and
close SW3 and SW4 (leave all switches
open for a maximum count of 15).
Switch SW5 (RESET) is normally
left open. It should be closed and
then opened again when· the camera
is set up to reset the film counter.
After that, it is only used to reset the
film counter if it counts down to zero.
If the unit is to be used on its own, .
connect it to the power supply shown
in Fig.Z(b). The unit can then be armed
or disarmed by connecting the Y terminal to GND and using a hidden
SC03103932
Fig.6: here are the full-size etching patterns for the two PC boards.
switch to connect the X terminal to
the +12V rail. This switch will have
to be located somewhere near the front
door, so that you don't trigger the unit
while you are leaving the house.
One last point: it's worth keeping
any security system like this a secret.
Word does get around.
SC
MARCH
1993
41
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