Some of our users have expressed an interest in using Cellular
Modems connected to our loggers so that a Text Message can be sent to a cell phone when an
Alarm Condition occurs. The cell modems (such as the Wavecom WMOD2B) have a special
command for sending text messages. At the end of the message the user needs to insert a
CtrlZ character. This capability was added to Omnilog in the second release of version
1.38 so if the logger is connected to a GSM Cell Modem, the Pager Dialout can be used to
send an SMS text message to a cell phone.
The AT command to send a Text Message is
AT+CMGS=number<CR>message<Ctrl Z>.
The number must be enclosed in double quotes.
The following example shows the Pager setup to send a Text Message
Via a GSM Cell Modem. The is done from the Pager page of the Logger Control Screen
Dial Out String
The AT+CMGS= instructs the GSM cell modem to send an SMS text message
The "+64210478847" is the phone number of the cell phone to send the message to
(note the double quotes)
The square box is a Carriage Return. It was inserted using the Add Ctrl Chr button with
the Control Character pulldown set to CR
Pager String
Browns Bridge Temp>32degC Is the text message that will be
sent to the cell phone
The square box is a Ctrl Z. It was inserted using the Add Ctrl Chr button with the Control
Character pulldown set to Ctrl Z
The Ctrl Z is required to terminate the text message
Setting the Alarm Condition
The alarm condition that will trigger the sending of the text message is setup in the
Alarms page of the Logger Control Screen. First we have to setup the condition that will
activate the Alarm (in this case Temperature greater than 32degC) and then we have to
select the Pager alarm to trigger when the condition occurs.
It is important to note that the Temperature channel must be
selected for logging in order for the alarm to activate and the logger must be running.
(see note on resetting alarms below)
Setting up the Cell Modem
The Logger is now setup and ready to send a text message when the alarm condition occurs
but we must setup the Cell Modem so that it is ready to accept the text message from the
logger. This is done in the "Setup Remote Modem" option in the "Tools"
menu. Connect the Cell Modem to be configured to a computer running the Omnilog software.
Note which comm port the cell modem is connected to. From the Tools menu select
"Setup Remote Modem". Select the correct comm port and "Wavecom GSM
Modem". Now click on the "Reset and Test Wavecom" Button. This tests the
communications with the Wavecom modem and resets it to its factory defaults. If the test
is OK click the "Send" Button. This sends the setup required by the logger to
the Cell Modem. The Modem is now ready for connection to the logger.
Connecting the Logger to the Cell
Modem
The download cables used with the HR series of loggers and the GP-MC logger are designed
to connect the logger to a computer. An adapter cable is required to connect the existing
download cable to a Wavecom Cell Modem. These cables are available for purchase or if you
can build your own. It is a 9pin D male to 9pin D male crossover cable with the following
connections
- Pin 3 to Pin 2
- Pin 2 to Pin 3
- Pin 4 to Pin 6
- Pin 6 to Pin 4
- Pin 5 to Pin 5
Resetting Alarms
Once an alarm condition has occurred and the text message has been sent, another text
message will not be sent until the alarm has been reset. This can be done in three ways:
- Restarting the logger when the Alarm condition has cleared
- Clicking the "Reset Alarms" Button on the Alarm Condition
Page of the Logger Control screen
- Setting up another alarm condition to automatically reset the alarm
(GP-MC only)
Note: the HR series of Loggers do not have "Clear Alarm"
conditions. This will be included in future releases of the logger firmware.
Method 1 and 2 involve connecting to the Logger with a computer and
manually resetting the alarm. Method 3 runs automatically with no user intervention
Automatically resetting an Alarm
The same method that is used to set alarms can be used to clear alarms. There is a
"Clear Alarm" check box for each of the six alarm conditions. When this is
ticked the alarm is cleared rather than triggered. So, for example, if we have a
temperature sensor in the field and want to use it as a frost alarm, we can set one alarm
condition (at a low temperature) to trigger the alarm and another condition at a higher
temperature to clear (reset) the same alarm. This way we will get a text message from the
pager alarm every time the temperature logger approaches frost conditions and not just
once when temperature first drops towards a frost. For our example we might choose to
trigger the alarm when the temperature drops below 3° C and Clear (reset)
the alarm when the temperature rises above 6° C. Our alarm setup would be
as follows:
As the temperature drops below 3° C the logger will
send text message.After the frost event when the temperature rises to above 6° C
the alarm will reset (no message will be set) and the alarm is now armed - ready to send
another message the next time the temperature drops below 3° C
