User guide

CS-GPRS Communications Package
2
• Can do a one way transmission to Loggernet or another logger (Senddata)
• Can open virtual serial ports to other dataloggers or sensors via the IP
network.
2. Hardware
The CS-GPRS package comprises an SC105 interface, an SC12 cable for
connection of the SC105 to the datalogger CS I/O port plus a cable to connect
between the modem port of the SC105 and the Wavecom modem. A mounting
bracket is also provided. The Wavecom modem can be fitted to one side of the
bracket and the SC105 on the other.
The Wavecom Supreme modem has been configured as is normal for the CS-GSM
packages. No additional setup is required of the modem, unless running the
modem at a higher speed than 9600 baud.
The SC105 interface will be shipped in the default setup, in SDC7 addressed mode
for the datalogger, with the serial port set to operate at 9600 baud in modem mode.
2.1 Power use considerations
The accompanying CS-GSM manual describes ways of minimising the power use
of the Wavecom Supreme modem, especially between calls, see Appendix B.
The power consumption figures for the modem between calls still applies as do
the program examples for cleanly shutting down the modem and restarting it.
However, if the modem is used in an “always-on” configuration, to allow instant
access, the modem will stay in a higher power state for most of the time. It is
critical to take this into consideration when considering suitable power supplies
and battery sizes.
When using an SC105 the average power consumption there is an open
PPP/GPRS connection the power use will typically be 30 mA. With only low
level traffic flowing through the connection the datalogger itself will often be able
to drop into a lower power state, i.e. not consume extra current. During
communications activity both the datalogger and modem power use will increase
significantly – the transmitter using an extra 100-200 mA depending on the
installation and speed of communication.
If, instead of the SC105 interface, you use a direct connection to the RS232 port or
SC-WMI interface, both of these interfaces will put in a high power state whilst
the PPP connection is active, plus the datalogger will remain in a high power state
throughout, using an extra 10-20 mA.
3. Network Contract and SIM card
The modem needs to be used with an airtime contract that allows GPRS
communications. Some SIMs are sold as “3G” compatible which means they can
be used in 3G phones too. It is important to check with your supplier that any
SIM supplied will work in a GSM/GPRS phone and that GPRS operation is
enabled and any 3G compatibility does not slow down the log-on process to the
network (which has been seen on UK O2 networks).
When buying a contract for GPRS the standard offering in Europe is that when
you connect you are allocated a dynamic, private IP address. This can be used
with Campbell dataloggers and is often the cheapest way to get a system up and
running. However, when operating in this way you can only have a limited
numbers of PCs or loggers connected to one logger and you lose the ftp, http and
some other functions as the logger cannot accept unsolicited calls made to it.