Monitor the voltage input to the SMC Gateway and detect mains loss/low battery and notify the customer via a text message.
When an SMC Gateway is installed out of sight, say adjacent to a fire alarm system it’s important that the gateway and attached radio is battery backed up. The 12V DC nominal supply that powers both the radio and gateway can be measured via the gateways built-in ‘volt meter’. This flow monitors the inout voltage, and sends a mains lost text message should the voltage input fail below 12V, and then sends a mains restored text message when the voltage goes over 13V.
1 - power-in
This node emits a message whenever the input voltage changes by more than 0.1V
2 - <12 or >13 [switch]
The switch node tests the incoming voltage (which is in the payload field of the message), and if it’s below 12 it sends it out of the first output, and if it’s over 13 it sends it out of the second output.
4 - Low [change]
This change node set the value of the topic field to “Low”. We need to do this for the Once node to work correctly (see 7 below).
6 - Restored [change]
This change node set the value of the topic field to “Restored”. We need to do this for the Once node to work correctly (see 7 below).
7 - once
The once node passes the first message it sees, and then ignores all further messages that have the same value in the choosen field(s). By default the once node works on the payload field, but our payload field will change as the voltage drops below 12V, e.g. 11.9, 11.8, 11.7 and each time the voltage changed the once node would see a different message and would therefore let it pass, and this would annoy the radio user!
By making the once node use just the “topic” field, and we set the topic field to be either “Low” or “Restored” only one message will be sent to the radio user each time the voltage drops below 12, and once again when it rises about 13.
8 - Group 1 [text-out]
This node sends the payload to the defined radio group, in this example group 1.
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