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Wireless Light Sensor
Fitting and operating instructions
1. Areas of application.
The wireless sensor model SR-LI Outdoor is a light sensor
based on wireless technology that measures the light
level in two lux ranges: 300-30,000 lx or 600-60,000 lx.
The light sensor transmits an RF telegram to a receiver
module, which using the correct function software can
switch the lights in the premises on or off.
Areas of application:
•
Signal transmitter to measure lux level for lighting,
barrier and blind systems.
•
Wireless transmission of the light level to a
system receiver.
•
Flexible installation with no wires.
•
Own power supply from solar cell and backup capacity.
2. Function.
The light sensor measures the light level continuously
and compares it with the RF telegram transmitted
earlier. In the event of a change in the light level of
more than 4 steps (1 step = 117 lx in the default lux
range, otherwise 234 lx), a relevant RF telegram will
be transmitted within 10 seconds.
In normal operation a current RF telegram will be
transmitted approx. every 17 minutes. This telegram
contains information on the sensor's light level,
address code and learn mode information. This RF
telegram can register a resolution down to 1 step,
which corresponds to 117 lx in the default lux range.
Measurement range:
The light sensor is designed to be installed outdoors on a
typical façade wall. We recommend installation higher
than 2.5 metres in order to reduce inconvenient lighting,
distracting shadows, vandalism, etc. There are two lux
ranges to choose between, making the measurement
range more dynamic for specific purposes.
3. Installation.
Location of the light sensor:
As the power supply is generated by the internal solar
cell, the light sensor must see a minimum of 400 lx
for more than 5 hours in order for there to be
sufficient energy to transmit the necessary RF
telegrams, even throughout the night.
Please note!
In order to achieve optimal transmission of the RF
signal, the light sensor should not be installed on large
metal surfaces, etc. These will drastically reduce the RF
signal between transmitter and receiver. Please refer to
section on RF wireless information.
Installation:
Optimal daylight measurement is achieved by
locating the light sensor with the front facing towards
the daylight, e.g. on a façade or gable end. Fig. 1.
Connection:
Simple, flexible installation without the use of wires
or batteries.
4. Settings.
Factory setting:
Lux .................................... 300 – 30,000 lx
T_coures ........................... 100
T_wake up ........................ 10 sec. See Fig. 2.
Setting up/testing:
The light sensor is equipped with an LRN mode
function, which is used for wireless system coding
towards a relevant receiver.
LRN button mode.
If you press this pushbutton (learn), a status RF
telegram will immediately be sent to a unique
address code and a lux level to the receiver. Fig. 2.
PS: The receiver must also be set to "Learn mode";
please refer to the receiver's software description of
the learning method.
5. RF wireless information.
The light sensor has an integrated RF transmitter model
STM100 (EnOcean). The transmitter's signal has a
frequency of 868 MHz. With a transmission frequency of
approx. every 1,000 sec. and a transmission output of
less than 10 mW, an RF environment is guaranteed that
is typically at least 100 times less than conventional
wireless systems.
RF transmitter distance:
As an RF signal involves electromagnetic oscillations/
waves (of a certain field strength), these are
suppressed on the way to the receiver.
The RF signal's field strength weakens proportionally
by the square of the distance between transmitter and
receiver (E,H ~ 1/r²). Fig. 3.
However, this natural reduction of the field strength as
a function of distance is not the only suppression that
affects the distance. Metal parts, e.g. in connection
with reinforcements to wall and ceiling elements,
metal foil in damp barriers or UV/colour filters through
metal foil will all reflect, distort or suppress the RF
signal on its way to the receiver.
Below is a list (approximate) of penetration rates for
commonly used building materials:
The penetrative strength of RF signals:
Materials
Penetration
Wood, plaster and
glass without surface foil ....................... 90...100%
Brick, MDF and chipboard panels ......... 65...95%
Concrete reinforcement ......................... 10...80%
Metal, aluminium panels, etc. .............. 0...10%
In practice this means that the choice of material has
a decisive influence on the distance between
transmitter and receiver. As a guideline, the following
distances can be used in typical wall constructions.
Visible distance between transmitter and receiver:
Typically 30 m in walkways, up to 100 m in large
rooms, e.g. sports halls.
Plaster/wooden walls:
Typically 30 m distance through max. 5 walls.
Brick/aerated concrete walls:
Typically 20 m distance through max. 3 walls.
Steel-reinforced walls/ceilings (floor structures):
Typically 10 m distance through max. 1 ceiling/wall.
If there is any doubt, check the distance before
securing to the building.
Other sources of noise for wireless RF signal transmission:
Devices that also operate with high-frequency signals,
such as computers, audio/video appliances, various
wireless systems, mobile phones, electronic trans-
formers, connection units and frequency converters are
considered to be a source of noise for a wireless RF
signal. We recommend a minimum distance of 0.5
metres from such devices.
RF transmitter rate of recurrence:
The light sensor transmits an RF telegram as a
function of an event-controlled process, but also in a
fixed, time-controlled process.
Measurement principle and telegram delivery:
The generation of a time-controlled process
(T_coures) takes place by activating the pushbutton
labelled "LRN", which starts the internal micro-
processor, gathers the status of the light sensor, and
transmits its value and address immediately via an
RF telegram to the receiver.
Creation of an event process (time-controlled). At a
suitable interval every 10 sec. (T_wake up), the
microprocessor is started and the status of the light
sensor is registered. If there is no change, for every
100 events (event-controlled) an RF telegram will be
transmitted to the receiver. This status is defined
when the light sensor does not register any change in
light of more than 4-5 steps, typically in darkness or at
a stable light level.
Recommended setup of STM100 transmitter:
T_wake up : 10 sec.
T_coures : 100
T_send = 10 sec x 100 = approx. 17 min.
A faster T_send will place a load on the power capacity
of the backup condenser, and a longer T_send will
reduce the resolution of the light level transmitted.
Description of the RF telegram:
2 byte Light Sensor ...... EnOcean transmitter STM100.
ORG (address code) ..... 7 digits (EnOcean type
designation "18F2")
Data_byte3 ................... Coding EXMC = 14 (232)
Data_byte2 ................... Coding EXMC = 300-
30,000 lx (0...255)
Data_byte1 ................... Coding EXMC = 600-
60,000 lx (0...255)
Data_byte0 ................... Bit DI_3 for LRN pushbutton.
6. Maintenance.
Dirt affects the operation of the sensor and the front of
the sensor must therefore be kept clean. Use a damp
cloth for cleaning. Use water with a standard detergent.
7. Technical data.
Supply voltage ................. Two split solar cells +
internal backup capacity
RF transmitter system ....... EnOcean STM100.
Transmission frequency ... 868 MHz.
Transmission output ......... <10 mW.
Transmission rate of
recurrence at default
setting ............................... An RF telegram is
transmitted every 17 min.
at light changes of less
than 4 steps. At light
changes of more than 4-5
steps, less than 10 sec. will
pass before an RF
telegram is transmitted.
RF range ........................... 300 metres in open space,
approx. 30 metres indoors,
see section "RF wireless
information".
Lux range 1 ...................... 300-30,000 lx,
117 lx/step STM100
PIN5 A/D0 (4LSB).
Lux range 2 ...................... 600-60,000 lx,
234 lx/step STM100
PIN6 A/D1 (5LSB).
Protection class ................ IP 54
Ambient temperature ...... -20°C...+55°C.
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