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Low-cost circuit controls outside lights
AUTOMATIC LIGHT
Wont to switch on outside lights
automatically when someone approaches
your house at night? This automatic
light controller will do the job.
By BRANCO JUSTIC
Many householders are now installing automatic light controllers
to monitor driveways, pathways
and other approaches to their
homes. These units typically employ
a passive infrared movement detector to detect the presence of body
heat and then automatically switch
on outside lights, usually for a
preset time.
Such systems enhance the safety
and security of your home as well
as adding convenience. You can
forget about fumbling for keys in
the dark or leaving outside lights on
for guests. Leaving lights on is often
a dead giveaway that a house is
unoccupied. With this type of
system, there is no need to leave
lights on; they will turn on
automatically when you or anyone
else approaches. And the reaction
of any intruder when lights suddenly switch on outside a home that appeared to be empty is obvious.
The automatic light controller
described here can be built for
around half the cost of commercial
units. It marries the Passive Infrared Movement Detector described in the December 1987 issue of
SILICON CHIP with a simple control
circuit. For the prototype, both circuits were housed in a sturdy electrical junction box fitted with a couple of floodlights, but this could be
varied to suit your particular
application.
In fact, many readers will probably elect to delete the floodlights
and simply use the controller to
switch existing outside lights. An
optional override switch allows the
lights to be switched on manually if
required.
Commercial sensors
Another option is to use the control board with a commercial PIR
detector or, depending on circumstances, with other types of
movement detectors. For example,
you could combine the control
board with the ultrasonic movement detector described last month
to automatically switch on hallway
lights or to light a stairway.
For outdoor use, the infrared sensor is the one to go for. This is
because it triggers only when it
detects body heat and cannot be
false triggered by other moving objects (eg, swaying tree branches).
Other types of movement detectors
would be virtually useless for outdoor use.
Naturally, the range of the unit
will depend on the type of detector
used. The passive infrared sensor
used here will give a useful range of
about 12 metres when fitted with
the wide-angle lens.
To make it as versatile as possible, the control board has two inputs, one for normally-open relay
contacts and the other for normallyclosed contacts. This means that it
should work with most types of sensors. A light dependent resistor
(LDR) on the control board monitors
the ambient light level and disables
the circuit during daylight hours.
Perimeter monitoring
The Automatic Light Controller uses a passive infrared sensor and is built into
a sturdy plastic case fitted out with a couple of floodlights. The lights switch
on for 40 seconds whenever the infrared sensor detects body heat.
56
SILICON CHIP
Provision has been made on the
control board for connecting
several units together in parallel,
for perimeter monitoring. When
this is done, all the controllers will
be activated if there is movement in
any one of the covered areas. The
lights then switch off only after the
CONTROLLER
+1 4V
PASSIVE
INFRARED
MOVEMENT
DETECTOR
MODULE
t
,--
0 11
47k
47k
®
_fL
INPUT 1
u
240V
LAMP(S)
D1 0
1N4148
INPUT 2
0.1
MANUAL
OVERRIDE
Sl
0. 1
LINK
0.1
250 VAC
47k
1M
GND
.,.
X
GND
D6
TO OTHER
CONTRDLLER/S
08
B
FROM OTHER CDNTRDLLER/S
t DELETE IF N/C CONTACTS NOT USED AT INPUT 1
AUTOMATIC LIGHT CONTROLLER
SCD3·1-0688
.,.
Fig.I: the control circuit can accept either high or low logic inputs from an external movement detector. When movement
is detected, pins 3 and 4 of IC2 switch high, the MOC3021 triggers, and Triac Qt turns on and lights the lamps.
timer in the last activated control
board has expired.
The units are interconnected using inexpensive low-current alarm
cable but note that each unit requires its own mains power connection. Of course, running two or
mor e units in parallel is entirely optional and can be ignored if you require only a single automatic light
controller.
How it works
Refer now to Fig.1 which shows
the circuit diagram of the control
board. It's built around a 4093 quad
Schmitt NAND gate, a MOC3021
optically coupled Triac driver, and
an SC151 Triac to switch the
lamp(s).
PARTS LIST
1 PIR movement detector (as
described in the December
1987 issue)
1 Clipsal No.265/4 Series H.D.
IP56 plastic case
1 printed circuit board, code
OE12 1
1 mains transformer with
11 VAC secondary
1 MPY 76C569 LOR
1 or more floodlights (see text)
Semiconductors
1 SC151 D Triac
1 MOC3021 Triac driver
1 40 93 quad NANO Schmitt
trigger
4 1 N4004 silicon rectifier diodes
6 1 N41 48 silicon signal diodes
Capacitors
1 4 70µ.F 25VW electrolytic
3 0 . 1µ.F monolithic
1 0 .1µ.F 250VAC metallised
polycarbonate
Resistors (0 .25W, 5%)
1 x 1 MO , 1 x 1 OOkO, 3 x 4 7k0, 2
x 2 .2k0, 2 x 4700, 1 x 1 OOkO
miniature trimpot
Miscellaneous
Screws, nuts , solder, hookup
wire, cable clamps, silicone
sealant.
JUNE 1988
57
In this version, the passive infrared movement detector was mounted on the lid of the case (right) while the control
board is mounted on the base. Note the insulating material covering the mains transformer terminals. Keep mains
wiring neat and tidy.
Power for the circuit is derived
from a mains step-down transformer. Its 10V AC output feeds a
bridge rectifier and 470µF 25VW
electrolytic capacitor to produce a
smoothed DC voltage of about 14V.
This DC voltage powers the control
board and the external movement
detector feither PIR or ultrasonic).
The control logic has two inputs,
designated Input 1 and Input 2 on
the circuit diagram. Input 1 is used
with external sensors employing
normally-closed relay (NC) contacts, while Input 2 is used with
sensors employing normally-open
(NO) contacts.
Let's consider Input 1 first. Normally, this input is held low by the
NC relay contacts and thus pin 12
of IC2c will also be low. This means
that pin 11 of IC2c will be high, pins
3 and 4 of IC2a and IC2b will be low
and the MOC3021 (ICl) will be off.
So Ql and the external lamp(s) will
also be off.
When the relay contacts open (ie,
when movement is detected), Input
1 is pulled high via a 47k0 resistor
and the resultant pulse applied via
D9 and a 100kn resistor to pin 12 of
IC2c.
Assume for the moment that pin
13 of IC2c is also high. Pin 11 of
Where to buy the parts
Parts for this project are available from Oatley Electronics, 5 Lansdowne
Pde (PO Box 89), Oatley, NSW 2223. Telephone (02) 579 4985.
Prices are as follows (mail orders add $3.50 p&p):
PCB plus on-board parts for PIR Movement Detector as
per December 1987 SILICON CHIP (lenses supplied) ................ $54.95
PCB plus on-board parts for Control Board (includes
transformer, terminal strip and the LOR) .... ... ...... ........... .... .. ... $24 .95
Note: copyright for the PCB artwork associated with this project is retained by Oatley Electronics.
58
SILICON CHIP
IC2c will now go low and the outputs of paralleled inverter stages
IC2a and IC2b will switch high.
These drive the LED inside the
MOC3021 which in turn triggers
the internal diac. This then turns on
Triac Ql via a lkO resistor to light
the lamp( s ).
Input 2 works in similiar fashion
except that it is normally held high
and is pulled low when the external
sensor is triggered (ie, a set of relay
contacts close, or a transistor turns
on). This low signal is then inverted ·
by IC2a and the resulting high applied to pin 12 of IC2 via DlO and
R7. After that, the sequence of
events is exactly as set out above
for Input 1.
Note that D9 and DlO together
form a simple diode OR gate (ie, input 1 or input 2 can deliver a. high
signal to pin 12 of IC2c). The 10okn
resistor and associated O. lµF
capacitor on pin 12 of IC2c form a
low pass filter. This stops false triggering due to noise and RF pickup
when long interconnecting cables
are used between the sensor and
the control board.
Daylight inhibit
Now let's look more closely at the
function of IC2c. Pin 13 of IC2c is
connected to a voltage divider consisting of VR1, a 2.2k0 resistor, a
4700 resistor, and the light dependent resistor LDR1. LDR1 is there to
stop the circuit from working during daylight hours.
This happens in the following
way. For IC2c to pass signals
through from its pin 12 input to its
output, pin 13 must be high (ie,
close to Vee). For this to happen,
the combined resistance of the
4700 resistor and LDR1 must be
much greater than the combined
resistance of VR1 and the 2.2kQ
resistor. This means that LDR1
must be in darkness (so that its
resistance will be very high).
During daylight, when light illuminates LDR1, its resistance will
be low and so pin 13 will be low and
no signals will pass through IC2c.
Trimpot VR1 sets the light level at
which the circuit will trigger.
When the lights turn on, the LDR
circuit is disabled by the O. lµF
capacitor connected to pin 13 of
IC2c. This works as follows.
When the outputs of IC2a and
IC2b go high to turn the lights on
(via IC1 and Triac Qt), the 0.1µF
capacitor is charged via the 4700
resistor and diode D5. This effectively latches the circuit up until
the timer in the sensor module turns
the lights off.
Inputs A, B and C and output X
allow up to four controllers to be
connected together in daisy-chain
fashion. In this configuration, the
output (X) _of each controller is connected to an input (A, B or C) of all
the other controllers.
Diodes D6, D7 and DB form an OR
gate so that the controller can be
activated by applying a high to any
of the inputs (ie, input A or input B
or input C). When an external controller is triggered, this high is applied via that controller's X output.
Thus, when one controller is triggered, it automatically triggers all
the other controllers and lights all
the lamps.
Construction
Most of the parts for the controller are installed on a printed
circuit board (PCB) coded OE121.
j_
---I.........
SWITCHED 240V AC
TD LAMPS
•
•
•
r:i ........... __._.
~
~1-D:-,m~ 470uF + ~O.l
05
X
<at>
e
. . , ; "'~
c'-!:'
c::..
B(/)
«::::)e
..cJ>,e
0.1\J
~ 8~-bJ§
1
GNO
0 :c:Jj
j
~\\ 1
r-.
{illg)e
QzDe
0.1
0~
•
!;;: :
• VR1
LDRl
D7
D~6
~
e[TI[)e
{ill[]e ~t
Dl~::;:
tDELETE IF NORMALLY CLOSED CONTACTS
NOT USED AT INPUT 1
PASSIVE INFRARED MOVEMENT DETECTOR
FRESNEL LENS
NOTE: CHANGE R15 TO 8.2M TO INCREASE
OH TIME TO 40 SECONDS
1J
Fig.2: mount the parts on the control board as shown here. Take care with the
mains wiring and note that some of the tracks on the board operate at mains
potential.
Fig.2 shows the parts layout.
Begin construction by installing
all the resistors and diodes, then install the larger components. Note
that the 47kQ pull-up resistor on Input 1 must be deleted if you don't in-
tend using this input. (Diode D9
could also be deleted in this case).
The resistor to be deleted is marked
with an asterisk.
The power transformer is
mounted directly on the PCB and is
JUNE 1988
59
CONTROLLER 3
Fig.3: here's how to wire two or three controller boards together for perimeter
lighting. When one controller switches on, it automatically triggers the others.
secured using screws and nuts.
Four insulated wire links are then
run between the transformer terminals and points on the PCB. An insulated terminal block terminates
the A, B, C, X and ground connections from other controllers, while
PC stakes are used for other external wiring connections.
Once completed, the control
board can be tested separately.
Connect mains wiring to the board
and connect the output to a 240V incandescent lamp. The LDR should
be left disconnected at this stage.
The board is now ready for
testing but, before plugging in,
check all wiring carefully. You
should also note that some of the
tracks on the PCB operate at mains
potential, so exercise extreme caution. In fact, we strongly recommend that you position the whole
assembly in the specified plastic
case before plugging it into the
mains.
Now switch on. If the 47k!l
resistor has been installed on Input
1, the lamp should light. The lamp
should then extinguish if Input 1 is
shorted to ground. If the 47k!l
resistor has been left out, the lamp
should initially be off but should
light when Input 2 is shorted to
ground.
If eveything works OK, disconnect the unit from the mains and
connect the LDR to its respective
terminals on the printed board.
Check that the unit now operates in
darkness but not in a well lit room.
VRl can be adjusted to set the ambient light level at which the lamp
will no longer turn on.
Finally, check that the DC output
voltage is around 14V.
The Passive Infrared Movement
Detector should be constructed and
tested as described in the
December 1987 issue of SILICON
CHIP. There's just one change to
make - the value of R15 should be
increased to 8.2M!l to increase the
on°time to approximately 40
seconds. In you want the lights to
remain on for longer than this, increase the value of C12 (use a lowleakage electrolytic of tantalum
type).
Final assembly
The two PCB assemblies are
housed in a sturdy plastic electrical
junction box made by Clipsal (type
No.265/4 Series H.D. IP56}. This
type of box is readily available from
electrical wholesalers and hardware stores (eg, BBC).
continued on page 68
Take care with component orientation when wiring up the control board. Note that the 47k!J resistor on Input 1 must
be deleted if you don't intend using this input.
60
SILICON CHIP
PARTS LIST
1 PCB, .code SC14-1-588,
11-2 x 69mm
1 Scotchcal label, 1 1 0 x
40mm
1 folded aluminium case, 133 x
76 x 54mm
1 finned heatsink, 7 5 x 11 0 x
33mm
1 panel mount 3AG fuse holder
1 SA fuse
2 6mm grommets
4 6mm standoffs
2 metres red automotive cable
(4mm dia).
2 metres black automotive
cable (4mm dia.)
4 3mm dia. x 1 5mm screws
4 3mm nuts
3 2.5mm dia. x 10mm screws
3 2.5mm nuts
1 solder lug
1 T0126 mica washer
1 T0-3 mica washer plus
insulating bushes
1 socket to suit plug on 7. 2V
Nicad battery pack
2 automotive battery clips
4 rubber feet
tery pack. Since the timer is also going to be adjusted during this procedure, you should also note the
precise time when the 12V source is
connected.
Assuming that the battery pack
Semiconductors
1 2N3055 NPN power
transistor
1 BD139 NPN transistor
1 BYX98-300(R) 1 OA 300V
diode
2 5mm LEDs (1 red , 1 green)
3 1 N4148, 1 N914 diodes
1 LM324 quad op amp
Capacitors
3 2200,uF 25VW PC
electrolytic
1 1000,uF 25VW PC
electrolytic
1 100,uF 25VW PC electrolytic
1 0.0 1,uF metallised polyester
Resistors (0 .25W, 5%)
1 x 1 OMO, 1 x 470k0, 1 x 27k0,
2 X 22kQ, 1 X 2.2k0, 1 X 6800,
3 X 1000, 1 X Q. 10 5W, 2 X
20k0 miniature vertical trimpots
Miscellaneous
Solder, heatsink compound,
tinned copper wire, etc.
was flat to begin with, it should
take about 20 minutes for the pack
to recharge. During this period, you
should carefully monitor the
temperature of the battery pack. If
the battery becomes hot, disconnect
Automatic light controller
The accompanying photographs
show the general layout inside the
case. As can be seen, the PIR movement detector is mounted on the lid
of the case, supported on 18mmlong pillars. Before mounting the
detector, you will have to make a
cutout in the lid to clear the lens
assembly. A 7mm hole will also
have to be drilled in the lid to accept the LDR.
The control board is mounted on
the bottom of the case and secured
using machine screws and nuts.
Drill holes to accept the mounting
screws plus an extra hole ih the
bottom left corner (looking from inside the case) for the mains cord entry. You will also have to drill a hole
in the adjacent end for the mains
cord clamp, plus additional holes in
68
SILICON CHIP
continued from page 60
the sides of the case to accept the
lamp holders (or to pass wiring to
external lamps, depending on
requirements).
It's best to complete the wiring to
the control board before mounting
it in the case. Light duty hookup
wire can be used for connections
between the two PCBs and to the
LDR but note that the wiring between the control PCBs and the
lamps must be run using 240V AC
cable. Lace up the cables or use
cable ties to keep the wiring tidy.
The control PCB can now be
mounted in the case and the mains
cord secured using a suitable
clamp. The prototype used a clamp
fashioned from scrap aluminium
and secured with a screw and nut.
This same screw and nut also
it from the charger immediately.
Under normal circumstances, the
battery pack should become warm
and the "charged" LED should light
at the end of the charging period
(ie, after about 20 minutes).
As soon as the "charged" LED
comes on, disconnect the battery
pack but leave the charger connected to the 12V source. Now
quickly connect your multimeter
(set to volts) between pin 1 of ICld
and ground and adjust VR2 so that
pin 1 switches high. This effectively
sets the timer so that it disables the
charger shortly after the end of the
normal charging cycle.
To check the timer action, disconnect the charger from the 12V
source, leave it for a minute or so to
discharge the circuit's capacitors
and then reconnect it, without a
nicad battery pack in place. Then
check that LED 2 comes on after 20
minutes.
When you are using the charger
and want to charge several battery
packs in succession, remember to
disconnect the charger from the
12V source after each pack is
charged. This resets the timer and
the voltage monitoring circuit.
Footnote: the Mega-Fast Nicad
Battery Charger can also be used to
charge lower voltage packs (eg,
5.6V nicad packs) without any
changes to the circuit.
lb
secures a piece of insulating
material to cover the mains terminations on the transformer. (In
the kit supplied by Oatley Electronics, this material will be
Presspahn or Elephantide ).
We suggest that the cut-outs for
the PIR lens assembly and the LDR
be weather-sealed using a silicone
sealant. If possible, try mounting
the unit under the eaves of the
house, out of the weather. A licensed electrician should be employed
to connect the unit to existing house
wiring.
Note: on boards presently being
supplied by Oatley Electronics, it is
necessary to modify the pattern
asssociated with the relay coil on
the PIR movement detector. Instructions on how to do this are being
supplied with the board (see Notes
and Errata on page 95).
lb
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