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2.5 More about the LED tool
The LED tool allows you to rapidly check the status of an A73x RTU. After you
insert the LED tool into the POWER connector, the unit waits up to two seconds
and then sends a broadcast frame (does not apply to the A733GSM/GPRS RTU). If
a nearby listening station or receiver decodes the frame, it will answer back—this
may take up to 10 seconds. When the RTU receives an answer, the LED tool lights
up for about 4 seconds. After another few seconds, the LED lights up one or more
times, depending on the number of stations/receivers that answered its broadcast
frame.
In addition, the LED always blinks briefly at 0.5 second intervals to indicate that the
unit is alive and the internal battery has enough energy to operate. If the blinking
interval lengthens to 2 seconds, the battery has become undercharged (that is,
under 5.6 volts but over 5.2 volts)—which is called the misery state. In this state,
an A73x RTU reduces its activities to a minimum. The radio unit is switched off, the
sensor sampling ceases, and no data is stored in the internal memory. Only the
internal real-time clock is maintained and the power management functions are
performed.
If the battery level drops below 5.2 volts, the system switches completely off,
effectively decoupling itself from the battery to protect it. In this case the LED tool
stays off permanently. An A73x RTU in such a situation will restart only after
connecting it to an external power supply (even a solar panel under low light
conditions).
Note:
New A73x RTUs are delivered with their internal batteries unformatted, meaning
they are completely discharged, and you should install them only on sunny days.
The battery will be fully charged after two consecutive sunny days, but you should
get an LED light-up after several minutes of charging in the sunlight.
Testing GSM/GPRS/A840 Connection with LED Tool
When the LED tool, the solar panel, or the SC cable is connected to the RTU, the
modem starts and tries to connect to the gateway. When you connect an LED tool,
the tool indicates the different states of the modem connection with blink-codes (for
details see below). What happens after the GPRS unit successfully connects to the
A840 Telemetry Gateway is determined by the configuration of the gateway. If the
"Close connection after poll" check box is checked, a poll cycle is conducted
immediately (and if the time is not yet set at the RTU, it will be set). If "Close
connection after poll" is not selected, a poll cycle is conducted according to the poll
settings on the gateway (either at the specified poll times or at the specified poll
interval). In this mode the time on the RTU will be set on the first poll cycle.
Misery state (battery voltage below 5.5V but above 5.2V): Short blink every other
second.
Normal mode, but GSM/GPRS modem not yet started: Short blink every half
second.
Modem in GSM mode (mostly transitional mode): 3 seconds on, half a second off.
Using the A73x RTU
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