! NB !
Crystal have stopped producing the DIL version of the CS8130. The SSOP version
doesn't fit the PCB, and is so small it's very difficult to solder by hand. We
no longer supply kits for this transceiver.
We the hope the following
information is of interest to some despite this.
The UPN Laser Transceiver (UPNLT) connects computers using laser beams.
A pair of UPNLTs can provide a full-duplex 115.2 kbit/sec data connection between the serial ports of two computers which are separated by a distance of many hundreds of metres. Once initialised, the UPNLTs are transparent to the computers and the computers see the connection as a hard-wired connection supporting TXD and RXD signals.
The UPNLT was designed as a physical layer link for the UPN, but it also has more general application where a data link between two computers is required and practical or cost considerations disallow the use of hard wired connection.
The major advantages UPNLTs have over other wireless technologies are
The major disadvantages of a UPNLT link are
The need for stable mounting is by far the most significant disadvantage. Building structures often move with time, temperature and wind. Building foundations also generally move. Anticipate at least monthly realignment for all but short (<100 metre) links between very stable buildings.
The UPNLT design is copyright. However, permission is granted to individuals, educational institutions and non-profit organisations to copy the design for their own use.
A review of the UPNLT appears in the Feb 1998 issue of "Electronics Australia" magazine.
Maximum range without additional lenses: 500 metres in clear weather
(note 1)
Recommended maximum range without additional lenses: 450
metres (allowing for loss through two clean, clear glass windows) (note
1)
Data rate: 1200 to 115200 bits/second
(configurable)
Mode: Full duplex, ie. data can flow in both directions
simultaneously
Signals supported: TXD and RXD.
Computer
interface: Pseudo-RS232. The UPNLT serial port signals do not swing
negative, as is specified for RS232. This is generally of no consequence, as
almost all computer serial ports treat a 0 volt signal as a negative
signal.
Maximum cable length from UPNLT to computer: 20 metres
(typ.)
Laser beam modulation/encoding: IrDA SIR
Laser
wavelength: 670 nm, visible red
Laser power: < 5mW peak pulse
power (2.8 mW typ.), < 1mW average power (.56 mW typ.) (note 1)
Laser
Class: Class 2, classification per AS/NZS 2211.1.1997 (note 1,
note 2, note 3)
Typical beam cross section: 5 mm x 2.5 mm at
collimating lens, 4.5 mm x 3 mm at waist, 150 mm x 75 mm at 500
metres.
Typical beam divergence: .3 mrad
PCB: 55 mm x 87 mm,
single-sided
Case dimensions: 65 mm x 115 mm x 31 mm
Power
requirements: 9 to 12 VDC @ 60 mA
Environmental: Ambient
temperature range 0 to 40 degrees Celsius. Protection from rain and direct
sunshine is necessary.
Vulnerability to environmental light:
Performance is degraded if the sun's position is within approx 15 degrees of the
receiver photodiode axis. Additional shielding can usually remedy this.
Reflected sunlight does not normally degrade performance.
Initialisation
requirements: Within 7 seconds of each UPNLT power-up, the attached computer
must send the UPNLT a configuration string at 9600 baud. Approximately 7 seconds
after power-up, a UPNLT switches automatically to data transfer mode.
Note 1:
The specifications and classification apply to UPNLTs
manufactured by REALTIME CONTROL. It is likely that UPNLTs made from kits
supplied by REALTIME CONTROL and adjusted in accordance with the instructions
will be similar, but this can not be guaranteed.
It is the responsibility of
the kit builder to determine the classification of any laser device they
build. The methods for determining classification depend on the particular
country's law, but generally require at least measurement of power output and
wavelength under various conditions.
It is the responsibility of the user of
a laser device to ensure that the law is complied with in the country where it
is used.
Note 2:
Extracts from AS/NZS 2211.1.1997
"9.2 Description of
Laser Class
Class 2: Laser products which emit visible radiation in the
wavelength range from 400 to 700 nm. Eye protection is normally afforded by
aversion responses including the blink reflex."
"Class 3B: Laser products
which emit either invisible or visible radiation and direct viewing is hazardous
to the eye. Class 3B lasers are capable of causing eye injury either because
their output is invisible and therefore aversion responses are not activated, or
because the beam power is such that damage is done in shorter time than the
blink reflex (.25 s). ..."
"11.4 Outdoor laser installations
11.4.1
Class 2 laser products Wherever reasonably practicable, the beam should
be terminated at the end of its useful path, and the laser should not be aimed
at personnel (at head height)."
"4.1.1 Modification If the
modification of a previously classified laser product affects any aspect of the
product's performance or intended functions within the scope of this Standard,
the person or organization performing any such modification is responsible for
ensuring the reclassification and relabelling of the laser product."
Note 3:
A Class 2 laser can cause eye damage if a person
deliberately forces himself to stare into the beam despite the strong natural
reflex to avert his gaze.
Laser and optical communication links
since 1/6/98
