Francis Searchlights A7138 User manual

User Instruction & Installation Manual
FH380 Remote Control
1200 Watt Metal Halide Searchlight
Product Reference Number:
A7138 –Variable Speed 240v 1200w
Manufacturer’s details: Distributor details:
Manual Part Number: C27538
2.11.17 Issue: 2
Francis Searchlights Ltd
Union Road, Bolton
Lancashire, BL2 2HJ, UK
Tel: [phone]
Fax: [phone]
http://www.francis.co.uk
E-mail: [e-mail]

CONTENTS
1 - Introduction
2 - Safety Precautions
3 - Technical Information
4 - Unpacking and Installation Instructions
5 - Electrical Installation
6 - Operating Instructions
7 - Fault Finding
8 - Maintenance and Servicing
9 - Wiring Diagram & General Assembly
10 - Spare Parts List

1 - Introduction
It is imperative that this manual is read carefully and understood before
installing your equipment. For your future reference please keep this
manual in a safe place.
Thank you for specifying a product from the Francis Searchlights range. All Francis products
are designed to give complete customer satisfaction and are manufactured to the highest
engineering standards in order to ensure optimum performance and service life.
The Francis Metal Halide range combines features proven over many years’ service in the
most hazardous conditions in both marine and land installations.
In order to prolong the life and performance of your product, we recommend that you only
specify Francis Searchlights spare parts. This will also ensure that any warranties on your
equipment will not be invalidated. Information on spares ordering and parts is provided in this
manual.
Should you ever need to contact Francis Searchlights Ltd. regarding your equipment, please
quote the Product Serial Number at all times.
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2 - Safety Precautions
The following instructions must be adhered to, in order to ensure a safe working environment
and the safety of the user.
Note: When unpacking or manoeuvring the searchlight into its fixing position, suitable
lifting points must be used in order to prevent damage to the equipment or personal
injury.
◼Because of the high internal pressure within the lamp, there is a risk of explosion in either a
hot or cold state;
◼During operation this lamp emits intense UV radiation which is harmful to the eyes and
skin. Suitable protection should be worn;
◼The high luminance of the arc can cause severe damage to the eye if viewed directly.
ALWAYS wear suitable protective goggles when viewing the lamp;
◼Always use protective sleeves supplied with the lamp;
◼Should it be necessary to examine the lamp with the front bezel removed, always use a
protective shield and wear goggles to ensure a safe working environment;
◼Searchlights get hot. Never touch the unit when lit and always allow 15 to 20 minutes for
cooling down after turning the searchlight off;
◼Never place anything on or cover the searchlight when in use;
◼Ensure the lamp has cooled sufficiently before removal;
◼If undue force appears necessary to remove the lamp, the equipment should be inspected
by a competent person or contact the manufacturer;
◼When disposing of lamps, return the lamp, via the supplier, to the lamp manufacturer in its
complete packaging;
◼Due to the vast range of lamps available it may appear possible that more powerful lamps
can be used in the equipment than for which it was designed. Even when the unit will
physically accept a higher wattage or voltage lamp, this substitution is not recommended
and is dangerous. This action will also void any warranties on the equipment.
◼Always refer to the lamp manufacturer’s technical data when dealing with lamps.
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3 –Technical Information
This product has been designed to operate in accordance with the product specification. The
FH380RC 1200 watt searchlight has the following features:
◼All marine grade materials and fixings;
◼Parabolic glass reflector;
◼Powder coated & stove enamel painted;
◼385° horizontal rotation;
◼Vertical movement +30˚ -35˚º;
◼Variable speed 1-23°/sec (Pan), 1-8°/sec (Tilt);
◼RS485 connectivity & auto home positioning;
◼Remote focus facility;
◼Instant lamp re-strike. No cooling down time required;
◼Economical 1000 hour lamp life;
◼Toughened front glass;
◼Luminous flux 110000;
◼Colour temperature 6000K;
◼G.R.P. control gear protected to IP66;
The searchlight also performs to the following optical data:
◼Metal Halide light source
◼Lamp Wattage - 1200 Watts;
◼Supply voltage - 220/240V;
◼Peak Beam Candlepower –33,700,000 lux;
◼Range –5805 metres;
◼Divergence –2°;
◼Temperature range: -50°C (with heaters fitted)
In order that the searchlight operates correctly it is imperative that competent personnel are
responsible for the installation, operation and servicing of this equipment. Failure to adhere to
this advice may cause premature failure or incorrect operation of the searchlight, which may
damage the equipment or cause personal injury.
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4 - Unpacking and Installation Instructions
The following instructions should be read and fully understood prior to installing the equipment
to ensure that the correct procedures are followed, and all safety precautions are observed.
Note: If the equipment has been in storage for a considerable amount of time, it is
advisable to conduct a routine maintenance check on all parts before installation.
Safety Precautions
This equipment should not be connected to an electrical supply before being installed.
Installation procedures should be adhered to in order to ensure a safe working environment
and reduce the risk of damage or personal injury.
Preparing the Mounting Position
Mark out and drill the fixing holes through the deck (refer to drawing C21501). If anti-vibration
mounts are to be fitted, the fixing holes for the mounts should also be marked out and drilled.
Prior to manoeuvring the searchlight into its’ fixing position, the AV mounts should be fitted to
the base. When in the desired position, bolt the searchlight firmly down. On and uneven
surface it may be necessary to use a suitable sealant such as silicone, in order to ensure a
weatherproofed joint.
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5 - Electrical Installation
Note: ~
When the main power is first applied to the searchlight, the searchlight will carry out a
self-test, it will Pan to the left limit and Tilt down to the limit, once this is complete, the
searchlight will then move to the centre and horizontal, during this please do not try and
operate the searchlight while this test is being carried out. Once the searchlight is back
at centre the searchlight can then be operated normally, by pressing the Panel button on
the control panel.
For safety purposes, only competent personnel should perform the electrical installation. All
equipment should be installed to current Electrical Regulations and Standards.
In order to obtain the maximum light output from the searchlight, it is essential that the full
operating voltage of the lamp fitted be applied to the lampholder contacts.
Method of Electrical Connection
1) Disconnect the supply before working on the electrical system;
2) The searchlight must be connected to a fused electrical supply, using suitably sized cable;
3) If the searchlight is located a considerable distance from the supply, provision must be
made in the cable size in order to overcome the voltage drop.
The Control Gear should NOT be positioned know more then 5 meters away from the
Searchlight.
The following table below indicates the maximum length of cable to be used for the AC
supply cable, from the junction box to the searchlight:
Searchlight
240v 1.2Kw
Cable Size (mm²)
Distance Max
1.5
62 MTRS
2.5
101 MTRS
4.0
160 MTRS
6.0
249 MTRS
10.0
417 MTRS
4) Whenever possible cable terminations should be made below deck and with approved
terminal devices;
5) If a spare auxiliary fuse or circuit breaker is not available, one of the correct type and rating
should be fitted and connected to a positive supply. It is advisable to locate a bus bar or
main connection and avoid any direct connection to the supply:
6) For 220v AC products, the following colour coding system should be used for the customer
supply cable:
Brown - Live
Blue - Negative
Green/Yellow - Earth
Note: This equipment must be earthed.

Installation Guideline
A typical installation and connection routine for the FH380RC searchlight is as follows:
Referring to wiring diagram C27424, a supply is fed to the junction box, which then provides a
common feed to the motor gearbox, control gear, searchlight and joystick panel.
The searchlight has been pre-wired with 3 meters of cable from the motor gearbox to junction
box provided. The searchlight head is pre-wired along with the connecting cable to the motor
gearbox.
Cables required to be connected by the customer: -
2 pair twisted 0.22mm 100ohm screened cable from the joystick panel to the junction box.
5 cores 1.5mm from the control gear to the junction box.
Supply cable to the junction box.
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6 - Operating Instructions
This equipment is designed for use out of doors, in free air. Never place anything on or cover
the searchlight when in use as this may present a hazard.
Switch On
The panel is activated using the PANEL button. This will illuminate brightly when the panel is
active. Alternate operations of the PANEL button will switch the panel on and off.
Lamp Control
When the panel is active pressing the LAMP, button will switch the lamp on or off.
If the control panel is switched off with the PANEL button the lamp will switch off.
Focus Control
The lamp focus can be adjusted using the FOCUS button. Lamp focus will adjust continuously
whilst FOCUS is pressed.
Beam Direction
The beam direction can be adjusted using the joystick when the panel is active. Moving the
joystick left or right will pan the beam clockwise or anticlockwise.
Moving the joystick up or down will move the beam up or down. The speed of movement is
proportional to the movement of the joystick. It is possible to move the beam in both directions
at once by moving the joystick diagonally.
Home
The lamp can be returned to a pre-set home position. By default, this is dead ahead with the
beam level although different positions can be programmed as described below.
To send the lamp to the home position switch the panel off then press the LAMP button.
Set New Home Position
To set a new home position move the lamp to the new desired home position. Switch the panel
off then press the joystick down to its limit and press the lamp button. The current position will
now be the new home position.
Set Motion Limit (only available when Remote Focus is fitted)
The lamp travel can be limited in either axis and either direction. To set a new limit switch the
panel on and move the lamp to the desired limit position. Switch the panel off then press and
hold the focus button whilst moving the joystick full travel in the direction of the desired limit.
Hold in this position for 4 seconds. For example, to set a limit to the tilt up motion; -
1. Switch panel on and drive lamp to desired tilt up limit position.
2. Switch panel off.

3. Press and hold the FOCUS button and hold joystick in the full up position for 4
seconds.
4. Tilt up motion will now be inhibited above the current position.
Clear Motion Limits
Motion limits as set above can be cleared by switching the panel off then pressing and holding
the focus button and lamp buttons together for 10 seconds.
Adjusting Panel Illumination
The panel illumination and indicators intensity can be adjusted to suit ambient light levels. To
adjust the intensity, switch the panel on then switch it off with the PANEL button and keep the
PANEL button pressed. To increase intensity, move the joystick to the right. To decrease move
to the left. Note that the panel button must be kept depressed whilst the joystick is moved. All
indicators will illuminate whilst adjustments are performed. Adjustment is complete when the
panel button is released.
Obtaining Fault Status
Fault codes can be accessed by switching the control panel on with the PANEL button and
keeping the PANEL button pressed for 10 seconds. Fault codes are indicated by the PANEL
button flashing a number of times related to the fault. Fault codes are detailed below. If more
than one fault is present the PANEL button will indicate them in sequence.
1. Pan Limit. –Either of the pan limit switches operated. Note that this
may not actually be a fault. The LED will flash when a limit switch is
operated under normal circumstances i.e. the lamp is at the limit of
travel. This will also indicate when a variable limit is reached.
2. Tilt Limit. –Either of the tilt limit switches operated. Note that this may
not actually be a fault. The LED will flash when a limit switch is
operated under normal circumstances i.e. the lamp is at the limit of
travel. This will also indicate when a variable limit is reached.
3. Pan motor over current. –The pan motor is taking excessive current.
The motor will be disabled for a period when this occurs. Fault
indication will remain until power is removed or the fault is corrected.
4. Tilt motor over current. –The tilt motor is taking excessive current. The
motor will be disabled for a period when this occurs. Fault indication
will remain until power is removed or the fault is corrected.
5. Focus motor over current. –The focus motor is taking excessive
current. The motor will be disabled for a period when this occurs. Fault
indication will remain until power is removed or the fault is corrected.
6. FBUS interface over current. –The speed control card supplies 24VDC
to the remote-control panels. This fault indicates the 24VDC output is
taking excessive current. The FBUS supply output will switch off. To

restore this output, remove the supply from the speed control card for a
period.
7. Anti-condensation heater output over current. –The 24VDC anti
condensation heater output is taking excessive current. The heater
output will switch off. To restore this output, remove the supply from the
speed control card for a period.
8. Limit Switch Error. Some lamp types do not use all or some limit
switches. If an invalid limit switch input is detected it is probable the
speed control card is set to the wrong product or there is a wiring error.
9. Datum Error. The start-up datum system has not completed correctly.
10.Product type not set or corrupt. The product type has not been set, has
been set incorrectly or is corrupt.
11.Supply voltage out of tolerance. The 24V supply is outside the range
18-30V.

Setting to Work
Safe service in use necessitates the strict observance of the following precautions.
◼Any article fabricated from quartz or glass is inherently fragile and care should
therefore be taken, at all times, when handling lamps;
◼Eye protection must be worn when handling lamps that have been removed from
their packaging materials. The protective sleeve should not be removed from the
lamp for safety reasons, as there is a remote possibility of the lamp shattering
violently, especially if it is subjected to mechanical shock or vibration;
◼Ensure that the power rating of the lamp to be fitted is suitable for the lamp house
and power supply equipment;
◼Always isolate the equipment from the supply before inserting a lamp;
◼Before inserting the lamp ensure that all contacts are clean. Contacts must be
renewed at the slightest sign of corrosion. Sanding or filing down corroded areas is
not recommended as this will only make the conducting surface between the pin
and lampholder smaller, thus causing the lamp to overheat;
◼Do not twist or bend the fused quartz bulb when fitting the lamp as mechanical
stresses MUST be avoided;
◼When inserting or removing a lamp, always hold it securely by its’ base in order to
prevent breakage between base and bulb;
◼The lampholder must not exercise mechanical tensions on the lamp, neither during
insertion or operation. Contacts must not discolour during use;
◼For safety reasons, the lamp should be replaced once it has reached its’ average
life, and not later than 1.25 times the stated life. With continuing use the risk of the
lamp exploding increases due to alterations within the quartz;
◼Before the protective sleeve is removed, suitable protection must be worn i.e face
mask and gloves with wrist protection;
◼Never touch the quartz bulb with bare hands, as fingerprints will make the glass
cloudy and cause a severe loss of light. This may also cause recrystallisation and
thus weaken the bulb material. Should the bulb be inadvertently touched, remove
fingerprints with methylated spirit and a clean, soft paper towel. The bulb should
then be wiped with distilled water. NOTE: ALWAYS WEAR MASK AND GLOVES
DURING CLEANING);
◼All packaging and the protective sleeve must be retained for re-use. Whenever
removing a lamp, the protective sleeve must always be used for safety reasons;
In all circumstances the lamp manufacturer’s data should be referred to when dealing
with lamps.
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FBUS SPEED CONTROL ASSEMBLY DETAILS
MAINS CONNECTORS
L Live.
N Neutral
E Earth
TILT CONNECTOR
MR Tilt Motor Red Wire (+)
MB Tilt Motor Black Wire (-)
ER Tilt Encoder Red Wire (5V). (Voyager Brown Wire)
EG Tilt Encoder Green Wire (Phase A Output) (Voyager Yellow Wire)
EW Tilt Encoder White Wire (Phase B Output)
0V Tilt Encoder Black Wire (Voyager Blue Wire)
Tilt Limit Switch Common Black Wire
UL Tilt up Limit Switch Orange Wire
DL Tilt down Limit Switch Blue Wire
PAN CONNECTOR
MR Pan Motor Red Wire (+)
MB Pan Motor Black Wire (-)
ER Pan Encoder Red Wire (5V)
EG Pan Encoder Green Wire (Phase A Output)
EW Pan Encoder White Wire (Phase B Output)
0V Pan Encoder Black & Pan Limit Switch Common
CL Pan Clockwise Limit Switch Orange Wire (As viewed looking down on lamp)
AL Pan Anticlockwise Limit Switch (As viewed looking down on lamp)
HEAD CONNECTOR
0 0V Common for Heater & Focus (If Searchlight has an igniter terminal is not used)
H Heater Active High Output
F Focus Motor Active High Output
S Focus position potentiometer.
FBUS CONNECTOR
0 OV out to Joystick Panels
T Line Terminate (Connect to + for terminate)
+ FBUS Data +
- FBUS DATA -
24 24V Supply out to joystick panels
24 VOLT INPUT
- Negative
+ Positive
LAMP RELAY
Relay input
Relay output

FBUS Speed Control Board

CONNECTIONS TO FBUS JOYSTICK CONTROL PANEL
FBUS CONNECTOR
0 OV Supply Input
T Line Terminate (Connect to + for terminate)
+ FBUS + RS485 Data In/Out
- FBUS - RS485 Data In/Out
24 +24V Supply Input
JOYSTICK CONNECTOR
BK Joystick Black Wire
Y Joystick Yellow Wire
BL Joystick Blue Wire
R Joystick Red Wire
FBUS JOYSTICK CONTROL BOARD

FBUS ADDRESS SWITCHES
OVERVIEW
FBUS uses two types of address switch. One type is rotary, and the value selected is the value
shown on the dial. The other type is rows of switches whose operation is described below: -
The switches all operate in the same manner producing a binary value with the highest binary
value to the left and the lowest value to the right. The values for each switch are listed below: -
SPEED CONTROL CARD LAMP ADDRESS
SWITCH NUMBER VALUE
SWITCH 4 16
SWITCH 5 8
SWITCH 6 4
SWITCH 7 2
SWITCH 8 1
STANDARD CONTROL PANEL –LAMP ADDRESS
SWITCH NUMBER VALUE
SWITCH 1 16
SWITCH 2 8
SWITCH 3 4
SWITCH 4 2
SWITCH 5 1
STANDARD CONTROL PANEL –PANEL ADDRESS
SWITCH NUMBER VALUE
SWITCH 1 8
SWITCH 2 4
SWITCH 3 2
SWITCH 4 1
Switching a switch to on, adds the binary value relating to that switch to the address value.
With all switches off the value is zero.

EXAMPLES
Standard control panel –panel address set to 5
Switch 1 = Off
Switch 2 = On (Value 4 added to address)
Switch 3 = Off
Switch 4 = On (Value 1 added to address)
4 + 1 = 5
Speed control card - lamp address set to 11
Switch 4 = Off
Switch 5 = On (Value 8 added to address)
Switch 6 = Off
Switch 7 = On (Value 2 added to address)
Switch 8 = On (Value 1 added to address)
8 + 2 + 1 = 11
ADDRESSING SYSTEM
The addressing system is very simple. Every lamp must have a unique address. The
addresses should be sequential and should start from zero. If there were three lamps in a
system the addresses should be set to 0, 1 and 2.
Control panel –panel addresses use the same system being sequential and start from zero.
It is essential that all lamp have a unique address with no duplication.
It is essential that all panels have a unique address with no duplication however note that
lamps and panels can be the same address. For example, on a system with two panels and
two lamps, the panel addresses will be 0 and 1 and the lamps addresses will be 0 and 1.
Control panel lamp addresses are defined by the system configuration. If two panels are used
to control the same lamp they must still have individual panel addresses but the lamp
addresses can be set to the same address value as the lamp which is to be controlled. Any
number of panels can control the same lamp.

FBUS DATA PROTOCOL
OVERVIEW
The Francis bus (FBUS) is a custom communication protocol based on
RS485 two wire bi directional communication hardware. The system provides
a simple bi-directional link between lamps and lamp control panels. The
system allows given panels to communicate with different lamps and also
allows a number of panels to communicate with the same lamp.
DETAILED DESCRIPTION
The FBUS system runs at 38.4K Baud. This low data rate facilitates longer
cable runs and complements the fairly small amount of data transfer required
whilst still providing a fast response. The data frame is 11 bits with 9 data bits,
one start and one stop bit. A simple error detection system is employed which
is described in detail later. Data is sent LSB first.
To prevent data collisions the system uses a polling technique. Lamp number
0 is the default bus master and controls timing of all communications by
polling other units connected to the bus. If lamp 0 is not operating or powered
down, lamp 1 automatically becomes the bus master as will lamp 2 if lamp 1
is not operating.
The system differentiates between address and data values by setting data bit
8 high for an address. Panel 2 address would therefore be sent as hex 102 or
binary 100000010. The lamps and panels use different address ranges with
panels being addresses 0-15 and lamp addresses starting at 16 and going up
to 56. A lamp whose address was set to 0 on the address switches will
actually be address 16 and would be transmitted as hex 110 or binary
100010000.
If lamp 0 is active this becomes the bus master and sequentially transmits the
full address range. No other units will transmit until they receive their address.
Each address is followed by a 1mS dead period where the master switches
from transmit to receive and monitors the bus for activity. If activity is present
the master will not transmit the next address until 1mS after bus activity
ceases. After the full panel address range has been sent (addresses 0-15) the
master starts to send lamp addresses.
These operate slightly differently in that, if more than three successive
addresses do not illicit a response, the bus master will assume the last lamp
has been polled and re starts the data cycle by reverting to panel address 0.
When a remote panel receives its address, it will send data if it has any to
send, if not, no data will be sent. Lamps operate differently in that they will
always send data after they have seen their address on the bus.
Panels can send data to any lamp therefore they transmit a modified lamp
address value prior to the lamp command(s). The modified address is
received by lamps and, if it matches their own address, the command(s)
which follow will be received and processed.
A detailed description of panel and lamp data follows.

PANEL TRANSMITTED DATA
Panels only send data when there is data to be sent i.e. there has been
activity at the panel which must be sent to a given lamp. If there is no data to
be sent, a panel will not transmit. The amount of data a panel sends will
depend upon the amount of activity at the panel and can be 2 to 10 bytes. The
commands described below are sent after a panel receives its address which
it uses as indication that it has a transmit time slot. Before any commands are
sent the panel must define which lamp the data pertains to. This is achieved
by preceding the command with a lamp address. Note that bit 7 is not set
when a panel defines the lamp to which it is to transmit. Lamps recognise the
address and receive data when the address matches their own. To send
commands to lamp number 2 a panel would precede the lamp command(s)
with the address value Hex 2, Binary 000000010. It is important to note that
multiple commands must be sent in numerical order i.e. a command with
value 01 must be sent before a command with 06 etc.
Panel transmit commands are listed below; -
DATA_PAN_JOYSTICK (Hex 01)
This is a two-byte command and must be immediately followed by another
byte whose value determines the lamps direction and speed. The value is
centred on 128 and has a range of 128 +/- 64. A value of 130 will make the
lamp rotate slowly clockwise. Increasing the value will make the lamp move
faster. A value of 126 will make the lamp rotate slowly anticlockwise.
Decreasing the value will make the lamp move faster. Transmitting values 01
then C0 would make the lamp pan clockwise at full speed.
DATA_TILT_JOYSTICK (Hex 02)
This is a two-byte command and must be immediately followed by another
byte whose value determines the lamps direction and speed. The value is
centred on 128 and has a range of 128 +/- 64. A value of 130 will make the
lamp point upwards slowly. Increasing the value will make the lamp move
faster. A value of 126 will make the lamp move down slowly. Decreasing the
value will make the lamp move faster. Sending values 02 then C0 would make
the lamp tilt up at full speed.
DATA_LAMP_BUTTON (Hex 0A)
This is a single byte command. The same command is sent to switch the lamp
on or off. This command must only be sent once for each press of the button.
Sending again will switch the lamp again. Basically, if the lamp was off,
sending this value will switch it on. If the lamp was on, sending this value will
switch it off. This technique is employed to facilitate simultaneous lamp control
from a number of different panels. Basically, what is sent is just information
that the lamp on off button has been pressed. How the lamp reacts to this
depends on the lamps current status. Most of the other lamp button
commands operate in a similar manner except the focus button. Confirmation
that the command has been received can be obtained by reading the lamp
status byte described below.

DATA_FOCUS_BUTTON (Hex 0B)
This is a single byte command. When the lamp receives this, it will run the
focus motor as long as the command remains. A panel will send this
command so long as the focus button is pressed.
DATA_HOME_BUTTON (Hex 0C)
This is s single byte command. A lamp receiving this will automatically move
to the pre-set home position. The command does not need to be maintained
while the lamp moves to home.
DATA_RECORD_BUTTON (Hex 0D)
This is a single byte command. The first time a lamp receives this command it
will enter record mode and start monitoring all movement and lamp switching
information. Recording will continue until the command is received again
when it will stop recording. As with most of the button commands it is
essential this command is just sent once. Confirmation that the command has
been received can be obtained by reading the lamp status byte described
below.
DATA_PLAY_BUTTON (Hex 0E)
This is a single byte command. The first time this is received a lamp will start
playing back any movement / lamp switching activities which were recorded
using the record function above. This will continue until the command is
received again or the lamp receives a move command
(DATA_PAN_JOYSTICK or DATA_TILT_JOYSTICK).
DATA_HOME_LP (Hex 0F)
This is a single byte command which activates when the home button is
pressed and held for 5 seconds (Home Long Press). This is used to store a
new home position. A lamp receiving this command will store the current
position as the value to move to when the home button is pressed normally.
Note that a lamp can only receive up to 10 bytes at a time. A panels transmit
sequence is the modified receiving lamp address followed by data commands
then the CRC. The CRC is formed by the sum of all the commands + the lamp
address value –note however that the address value used in the CRC is the
unmodified value (Bit 7 clear).
DATA_PAN_POSITION (Hex 18)
This is a three-byte command. Following the DATA_PAN_POSITION
command two data bytes specify the position to which the lamp must move.
The bearing resolution is 0.1 degrees. The value is sent LSB first with the first
byte representing the lower position command bits. The MSB (sent last) lower
4 bits represents the remaining value. The position value is centred on 2048
(Binary 1000 0000 0000) so a value of 2048 would make the lamp move to
the dead ahead position. An increasing value represents a clockwise motion
with a resolution of 0.1 degrees. A value of 2058 would therefore represent 1
degree clockwise (2058 = 2048 + 10 –but resolution is 0.1 degrees so a
value 10 = 1 degree). Values below 2048 represent anticlockwise motion so a
value of 1048 would represent an angle 100 degrees anticlockwise of centre.