The SN935-DT motion sensor combines dual technology motion detection
with wireless Spread Spectrum RF in one small, attractive package.
Within the protected area, the passive infrared (PIR) detector senses
changes in infrared energy (such as body heat emitted by an intruder), and
turns on the microwave detector which senses the motion. Both technolo-
gies must verify intrusion within a preset time interval,
virtually eliminating
false alarms.
To reduce current drain and prolong battery life, the microwave circuitry
is dormant until the PIR detects a change in the infrared energy level.
In addition, the SN935-DT sensor features a supervision circuit that monitors
the microwave technology. If a problem is detected, the sensor will go into
alarm.
The SN935-DT sensor is also equipped with both a Fresnel lens and multi-
segmented PIR mirror. This unique optical system provides dense PIR
coverage from directly beneath the unit to maximum range.
Installation Instructions
Select the best location in the room for both technologies. Aim the sensor
toward the interior of the room, away from windows, moving machinery, and
heating/cooling sources. Do NOT mount the detector near wire screens
or large metal objects. We recommend that you verify the RF reception
prior to permanently mounting the sensor.
Maximum range is obtained at a
mounting height of 7'6" (2.3 m).
Make sure the sensor has a clear line
of sight to all areas you wish to
protect. Infrared energy cannot
penetrate solid objects. If the PIR is
blocked, the unit will not alarm.
PCB
Mounting
Hole
Knockouts
Rear
Housing
Front Housing
Tamper Switch
Activator
Figure 1
SN935-DT Assembly
Mounting Procedure
Features
Use the sensor's rear cover to mark
the mounting holes. To remove the
sensor's rear cover, use a small-blade
screwdriver to push up on the latch
through the slot in the bottom of the
front housing. Gently pull the hous-
ings apart at the base first.
The printed circuit board (PCB) is
mounted in the front housing. Do
NOT remove the PCB.
Securely mount the rear housing at the desired location. When mounting
the sensor on a wall, use the two knockout holes in the back of the rear
housing. When mounting the sensor in a corner, use the knockout holes
on the beveled corners of the unit. Remove the knock-outs, mark and drill
the mounting holes, and mount the transmitter at the desired location. Install
the batteries and replace the cover.
®
SpreadNet
Model SN935-DT
RF DUAL TEC
®
Microwave/Passive Infra-Red
Transmitter
• Microwave/PIR technology
• Dual element PIR
• Microwave supervision
• Two-minute holdout circuit
• Cover tamper switch
• Automatic walk-test mode
• 100 mW transmitter power (max)
• Simple installation
• Spread Spectrum technology
• Unique PIR optics
• Single edge PIR triggering
• Lithium batteries included
• Optional barrier and pet-alley
lenses available
• Programmable supervisory rate
• EEPROM memory
Mounting Location
Pull apart the
front and rear
housings at the
base first
Installing the Batteries
The SN935-DT can operate on 2 AA lithium batteries. For increased life,
however, the unit can accommodate 4 batteries. The batteries must always
be installed and replaced in pairs.
Four batteries, shipped with the unit, must be installed prior to testing. Proper
orientation is shown in Figure 2.
NOTE: To prevent excessive battery drain during setup and installation,
you should remove the batteries whenever the cover is open and
the unit is not being tested.
Programming the Transmitter
To program the transmitter, refer to the SN900-PROG Programming Manual
(P/N 5-051-136-00).
System Testing
Opening the front cover of the SN935-DT signals a tamper condition and
automatically places the unit in the walk-test mode. This also disables the
two-minute hold out circuit. The unit remains in this mode for a period of
8 minutes after the cover has been replaced. There are two walk-test LEDs
located at the bottom of the unit behind the lens, one on each side. These
LEDs are only active while the unit is in the walk-test mode.
Walk-Test
Programmer
Range
Adjust
Spread
Spectrum
Antenna
Test/Alarm
Jumper
ALARM
PIR
Test/Alarm
Jumper
Tamper
Switch (S1)
Figure 2
PCB Layout and
Connections
A jumper at the bottom of the PCB, next to the Tamper Switch (S1), allows
you to test the PIR section separately. Placing the jumper in the "PIR"
position, as shown in Figure 2, allows you to walk-test the PIR without
activating the microwave circuits. The range of the PIR detector is not
adjustable. The PIR's field of view (range) is determined by the mounting
height and the type of lens installed.
Microwave Supervision
Walk-testing the SN935-DT motion sensor is a two-stage process. The first
step is to walk-test the PIR. Walk across the protected area at the ranges
to be covered. Two to four normal steps should make the LEDs light. Since
the LEDs are connected in parallel, both LEDs will light at the same time.
When there is no motion in the protected area, the LEDs should be off. The
second stage is to adjust the range of microwave transmitter. For continued
reliability, the sensor should be walk-tested at least once per year.
Returning the jumper to the ALARM position will reactivate the microwave
circuits. Remember that as long as the cover is open, the holdout circuit
remains disabled. In order to adjust the microwave, the PIR must first see
motion which will activate the microwave circuitry.
There is a microwave range potentiometer located near the center of
the printed circuit board below the battery holder (refer to Figure 2).
With the PCB oriented in its correct mounting position and facing you,
turning the potentiometer clockwise will INCREASE the range of
the microwave.
After determining the field of view for the PIR, set the microwave range
potentiometer at MINIMUM by turning it counterclockwise as far as it will go.
(Use a small screwdriver to turn the range potentiometer.) Then, with the
test jumper in the ALARM position, walk-test the sensor, gradually increasing
the sensitivity of the microwave until the desired range is obtained.
Range Adjustment
If the microwave technology stops sending or receiving signals, the sensor
will lock into an alarm. The LEDs at the sensor, however, will not light.
If the microwave regains its signal, the sensor will return to normal
operation.
Microwave Antenna
Walk-Test LEDs
