Lightware SF10 User manual

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SF10
SF10
Laser altimeter Product manual
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014110
The SF10 is a compact, lightweight
laser altimeter for above-ground-
level altitude measurement from
small fixed wing or rotor craft.
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The SF10 laser altimeter is ideal for
automated landings and precision
hovering.
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The configurable features and
multiple hardware interfaces make
the SF10 easy to use with different
types of flight controller.
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The SF10 laser altimeter uses a time-
of-flight system to make accurate
distance measurements to natural or
artificial surfaces.
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Features:
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•Very compact and lightweight - 35 grams.!
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•Accurate AGL altitude measurement up to 50
meters on most natural and artificial surfaces.!
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•Fast update rate of 16 readings per second.!
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•Includes serial, I2C, USB and analog interfaces
with programmable capabilities.!
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•Easy to configure using the built-in menu and
LightWare Terminal software.!
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•Fully calibrated and ready to run.!
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•Accurate, reliable altitude measurements in
sunlight or dark conditions.!
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•Not affected by: speed; wind; changes in
barometric pressure; noise; ambient light; terrain
or air temperature.!

www.lightware.co.za • [email protected]
SF10
SF10
Laser altimeter Product manual
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Table of contents
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Table of figures
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Figure 1 :: The main features of the SF10 3................................................................................................................
Figure 2 :: Power from the USB port 5.....................................................................................................................
Figure 3 :: Regulated +5 V DC power supply connections 5..............................................................................................
Figure 4 :: USB communications 5...........................................................................................................................
Figure 5 :: Analog voltage connections 6...................................................................................................................
Figure 6 :: Serial interface connections 6..................................................................................................................
Figure 7 :: I2C interface connections 6.....................................................................................................................
Figure 8 :: LightWare Terminal showing menu options 7.................................................................................................
Figure 9 :: Altitude represented by distance (Serial / I2C) and analog voltage 8....................................................................
Figure 10 :: Labelling on the SF10 9.........................................................................................................................
Figure 11 :: Dimension drawings of the SF10 10...........................................................................................................
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Disclaimer
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Information found in this document is used entirely at the reader’s own risk and whilst every effort has been made to
ensure its validity neither LightWare Optoelectronics (Pty) Ltd nor its representatives make any warranties with respect the
accuracy of the information contained herein.
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1. Overview 3...................................................................................................................................................
2. Quick start guide 4.........................................................................................................................................
3. Making connections to the SF10 5........................................................................................................................
4. Menu options 7..............................................................................................................................................
5. Instructions for safe use 9.................................................................................................................................
Appendix A :: Specifications 10..............................................................................................................................
Appendix B :: Dimensions 10.................................................................................................................................
Revision history 10.............................................................................................................................................
SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014210

www.lightware.co.za • [email protected]
SF10
SF10
Laser altimeter Product manual
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1. Overview
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The light-weight, SF10 laser altimeter is an essential addition to any scale aircraft that needs fast, accurate and reliable AGL altitude
measurements.
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Operating from a regulated 5 V DC supply, the SF10 includes both analog and digital interfaces that can be easily connected to a
flight controller or a standard processing platform. Each interface on the SF10 can be configured using a simple software menu that
is accessible through the built-in, micro USB port.
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The SF10 works by measuring the time it takes for a very short flash of laser light to travel to the ground and back again. The
accuracy of the measurement is not affected by the colour or texture of the ground nor the angle of incidence of the laser beam.
The SF10 is virtually immune to background light, wind and noise making it the ideal AGL altimeter for all kinds of terrain.
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The maximum operating altitude of the SF10 is more than 50 meters and readings are updated 16 times per second. There is a
‘damping’ option to reduce any unwanted variability in the altitude introduced by uneven terrain, bushes or long grass.
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Figure 1 :: The main features of the SF10
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014310

www.lightware.co.za • [email protected]
SF10
SF10
Laser altimeter Product manual
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2. Quick start guide
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1. CAUTION - The SF10 laser altimeter contains a laser and should never be aimed at a
person or an animal. Do not look at the beam directly with optical instruments.
2. Plug a USB cable into the SF10’s micro USB connector and connect the other end into a
PC. This provides both power and communication for the unit.
3. Download LightWare Terminal software from www.lightware.co.za onto your PC. Open
the installer package and follow the installation instructions. Everything needed for
communicating with SF10 will automatically be installed.
4. Start the LightWare Terminal software and click the “Connect” icon to open a
communications port. The distance measurements should begin to scroll in the Terminal
window. If the connection isn’t made automatically then click the “Laser” icon and
select the correct port from the list shown.
5. The configuration menu inside the SF10 is accessed by pressing the <space bar> key on
your keyboard. This stops the measurements and displays a list of settings. Pressing the
<space bar> key again restarts measuring.
6. A summary of the settings is given below:
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7. Once you have confirmed your settings, make sure the SF10 is measuring correctly then click the “Disconnect” icon and
disconnect the USB cable from the SF10.
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8. There are several interface options available on the main connector. These connections are used to integrate the SF10
into your system and details of all the options are explained later in this document.
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Setting
Range of values
Description
a: Serial port baud rate
9600 … 115200
Sets the baud rate for the serial port
b: I2C bus address
0 … 2E
Sets the I2C address
c: Analog 2.56 V altitude
1.00m … 60.00m
Sets the altitude at which the voltage output will show 2.56 V
d: Ground offset
0.00m … +10.0m
Adjusts the zero point from which measurements are taken
e: Damping
0 … 10
Sets the damping coefficient to smooth the readings
SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014410

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SF10
SF10
Laser altimeter Product manual
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3. Making connections to the SF10
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The SF10 gets power from either a regulated +5 V DC supply on the main connector or via the USB port when it is connected to a PC.
There are a number of digital and analog interfaces on the main connector and either one or a combination of interfaces may be
connected to a host controller. The built-in micro USB port can be used to input settings and to test the performance of the SF10.
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Power supply option 1: USB
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The SF10 can be powered directly from the USB port of a PC or laptop. This is particularly useful for testing the SF10 before it is
installed in your system and also for changing the settings in readiness for the final application.
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Figure 2 :: Power from the USB port
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Power supply option 2: Regulated +5 V DC
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The second power supply option is to connect a regulated voltage of 5 V ± 10% DC to the main connector. If the power wires are more
than 30 cm long, we recommend using a decoupling capacitor, or other noise suppression components to reduce the chance
interference being picked up on the power wires.
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Figure 3 :: Regulated +5 V DC power supply connections
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Communications using the USB port
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The SF10 has a micro USB port that can be used to communicate with LightWare Terminal software on a PC. This connection also
provides power to the unit thereby presenting a quick way to test and configure the SF10. The LightWare Terminal software will
automatically detect the USB port that is connected to the SF10 and communications can be established by clicking on the
“Connect” icon. If more than one compatible device is present, click the “Laser” icon to select which USB port should be active.
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Once communication has been established, settings can be changed by pressing the <space bar> key to access the menu and then
selecting the menu item that needs changing. Pressing the <space bar> key again restarts the measuring process. If no settings are
entered then the SF10 automatically restarts after two minutes. More details of the menu items are discussed in the “Menu options”
section below.
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If you want to use a different serial emulation program then the USB serial protocol should be set to 115200 baud with 1 stop bit and
no parity or handshaking. All communications are in standard ASCII format.
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Figure 4 :: USB communications
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014510

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SF10
SF10
Laser altimeter Product manual
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Analog voltage interface
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The analog interface on the main connector produces a linear voltage of between 0.00 V and 2.56 V that is proportional to the
measured altitude. The physical altitude in meters that equates to 2.56 V can be adjusted through the USB menu system. For
example, an altitude setting of 51.20 meters would produce a linear voltage output of 50 mV per meter.
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Figure 5 :: Analog voltage connections
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Serial interface
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The serial interface on the main connector outputs the measured altitude in meters as an ASCII encoded number. This interface uses
3.3 V logic levels and can be connected directly to any similar, compatible interface. Distances are transmitted whenever the SF10
receives an ASCII character from the host controller. This character may have any value in the extended ASCII character set. The
baud rate for the serial interface is selectable through the USB menu system. The maximum delay between receiving a character and
returning the altitude is 25 ms. !
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Figure 6 :: Serial interface connections
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I2C interface
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The I2C interface on the main connector outputs a value that represents the altitude in centimetres. This interface operates in
“slave” mode and uses 3.3 V logic levels. The I2C address can be set through the USB menu system. The host controller acts as the
I2C “master” and sends the address to the SF10 as an 8 bit value. The SF10 then returns the altitude as a 16 bit integer. The
maximum delay between receiving the address and returning the altitude is 25 ms.
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Figure 7 :: I2C interface connections
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014610

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SF10
SF10
Laser altimeter Product manual
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4. Menu options
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The SF10 can be connected through the on-board USB port to a Terminal emulation program running on a PC. The LightWare Terminal
software is available for download from www.lightware.co.za.
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Once the USB connection is made, the Terminal window displays the distance reading from the SF10. Pressing the <space bar> key
stops the measuring process and changes the display to a menu that lists all the available settings and configuration options. Pressing
the <space bar> key again restarts the measuring process. If no changes are made, the unit will automatically begin to measure
again after two minutes.
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Figure 8 :: LightWare Terminal showing menu options
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a: Serial port baud rate (9600 … 115200)
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The serial port transmits a serial string of ASCII encoded data from the SF10 to the host controller. The baud rate of transmission is
selected by menu item <A> and toggles through the standard baud rates from 9600 to 115200. By default, there is 1 stop bit and no
parity or handshaking on this serial port.
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The ASCII string representing the altitude is in floating point format with two decimal places followed by carriage return and line
feed:
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“22.48\r\n”
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where carriage return and line feed are given by the hexadecimal ASCII characters:
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\r = 0x0D
\n = 0x0A
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The altitude is sent out of the serial port when any ASCII character is transmitted by the host controller to the SF10.
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b: I2C bus address (0x00 … 0xFF)
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The I2C bus operates in slave mode and accepts an 8 bit address before responding with a 16 bit, binary coded integer that is the
altitude in centimetres. The address can be set by selecting menu item <B> and is entered as an bit, hexadecimal number.
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014710

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SF10
SF10
Laser altimeter Product manual
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c: Analog 2.56 V altitude (1.00 m … 60.00 m)
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The altitude at which the maximum analog output of 2.56 V occurs can be set by selecting menu item <C>. The output voltage can
be converted back into an altitude by using the formula:
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a = v / 2.56 * c
where:
a = measured altitude
v = voltage measured by the ADC of the host
c = 2.56 V altitude setting
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The analog voltage output updates 16 times per second and has a 12 bit resolution.
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Figure 9 :: Altitude represented by distance (Serial / I2C) and analog voltage
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d: Ground offset (0.00 m … 10.0 m)
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The point from which altitude measurements are taken can be adjusted using menu item <D>. The range of values that can be
entered are from 0.00 meter to +10.00 meters and this value is subtracted from the altitude reading before it is made available on
any of the interfaces. The ground offset can be used to compensate for the mounting position of the SF10 in the airframe, where
distance readings may best be interpreted from a suitable point on the landing gear, rather than from the front face of the SF10.
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e: Damping - Sets the damping coefficient to smooth the readings (0 … 10)
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Menu item <E> is a damping coefficient that can be any integer value from 0 to 10. This value is used to reduce the effects of scrub,
bushes and long grass on the mean altitude reading. Higher values produce a smoother output. Note that this coefficient changes the
time constant of the altitude measurements and therefore the rate of response.
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SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014810

www.lightware.co.za • [email protected]
SF10
SF10
Laser altimeter Product manual
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5. Instructions for safe use
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The SF10 is a laser range finder that emits ionizing laser radiation. The level of the laser emission is Class 1M which indicates that
the laser beam is safe to look at with the unaided eye but must not be viewed using binoculars or other optical devices at a distance
of less than 15 meters. Notwithstanding the safety rating, avoid looking into the beam and switch the unit off when working in the
area.
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CAUTION -- The use of optical instruments with this product will increase eye hazard.
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The SF10 should not be disassembled or modified in any way. The laser eye safety rating depends on the mechanical integrity of the
optics and electronics so if these are damaged do not continue using the SF10. There are no user serviceable parts and maintenance
or repair must only be carried out by the manufacturer or a qualified service agent.
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No regular maintenance is required for the SF10 but if the lenses start to collect dust then they may be wiped with suitable lens
cleaning materials. Make sure that the SF10 is switched OFF before looking into the lenses.
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The SF10 should be mounted using the four holes provided in the circuit board. Do not hold or clamp the lens tubes as this may cause
damage and adversely affect the laser safety rating.
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Laser radiation information and labels
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Figure 10 :: Labelling on the SF10
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Specification
Value / AEL
Notes
Laser wavelength
905 nm
Pulse width
< 30 ns
Pulse frequency
< 35 kHz
Peak power
< 20 W / 25 W
50 millimeter aperture at 2 meters
Average power
<4 mW / 5 mW
7 millimeter aperture
Average energy per pulse
<0.60 nj / 200 nj
NOHD
<15 m
Distance beyond which binoculars with may be used safely
SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 2014910

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SF10
SF10
Laser altimeter Product manual
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Appendix A :: Specifications
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Appendix B :: Dimensions
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Figure 11 :: Dimension drawings of the SF10/A
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Revision history
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SF10/A
Range
0 … 50 meters (natural targets)
Resolution
1 centimeters
Update rate
16 readings per second
Accuracy
±(0.03 + 0.1%) meter
Power supply voltage
5.0 V ± 0.5 V DC
Power supply current
150 mA (maximum)
Outputs & interfaces
Serial, I2C & analog with maximum latency of 25 ms
Dimensions
30 x 55 x 50 millimeters
Weight
35 grams (excluding cables)
Connections
Plug & socket, micro USB
Laser power
20 W (peak), 15 mW (average), Class 1M
Optical aperture
51 millimeters
Beam divergence
0,2°
Operating temperature
0 ... 40°C
Version
Date
Authors
Comments
Rev 0
2014/07/12
JEP
First edition
SF10 Laser Altimeter - Product Manual - Revision 0 !of !© LightWare Optoelectronics (Pty) Ltd, 201410 10