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FB_RS485_EASTRON_SDM_POWER_MQTT.md

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FB_RS485_EASTRON_SDM_POWER_MQTT

General

Used to process Modbus RTU data through RS485 to human understandable values and publish data updates through MQTT if desired. This function block aims to read power consumption from a range of Eastron SDM power meters. Currently the Eastron SDM120, SDM220 and SDM630 are supported.

Eastron SDM120 datasheets:

Eastron SDM220 datasheets:

Eastron SDM630 datasheet:

Block diagram

OUTPUT(S):

  • ACTIVEPOWER: datatype real.
  • DataAvailable: datatype bool, high when data is available read by modbus read commando. This means the output is only low on startup until modbus read commando has been executed successfully.
  • Error: datatype bool, high when an error occured while executing modbus read commando.

METHOD(S)

  • InitMQTT: enables MQTT events on the FB, an overview of the parameters:
    • MQTTPublishPrefix: datatype POINTER TO STRING, pointer to the MQTT publish prefix that should be used for publishing any messages/events for this FB. Suffix is automatically set to FB name.
    • pMqttPublishQueue: datatype POINTER TO FB_MqttPublishQueue, pointer to the MQTT queue to publish messages.
  • InitRS485: configures the Modbus RTU device address and the execution/polling interval for the modbus read command.
  • RequestBusTime: method implemented by each RS485 device function block. More information in the RS485Device interface docs.
  • GetRtuQuery: method implemented by each RS485 device function block. More information in the RS485Device interface docs.
  • ProcessDataArray: method implemented by each RS485 device function block. More information in the RS485Device interface docs.

MQTT Event Behaviour

Requires method call InitMQTT to enable MQTT capabilities.

Event Description MQTT payload QoS Retain flag Published on startup
output is updated the output is updated. real value 2 FALSE no

MQTT publish topic is a concatination of the publish prefix and the function block name and a unique value:

output MQTT topc suffic Unit
ACTIVEPOWER /ACTP Watts

Code example

  • variables initiation:
MQTTPubRS485Prefix                :STRING(100) := 'Devices/PLC/House/Out/RS485/';
FB_RS485_EASTRON_SDM_POWER_001    :FB_RS485_EASTRON_SDM_POWER_MQTT;
  • Init RS485 method call (called once during startup):
FB_RS485_EASTRON_SDM_POWER_001.InitRS485(
	DataPollingInterval := T#15S,                     (* Polling interval for data array *)			
	DeviceAddress := 1,                               (* Device address of the modbus device *)
	DeviceType := RS485_EASTRON_SDM_Devices.SDM630    (* Type of Eastron SDM device *)
);
  • Init MQTT method call (called once during startup):
FB_RS485_EASTRON_SDM_POWER_001.InitMqtt(
	MQTTPublishPrefix:= ADR(MqttRS485Prefix),                       (* pointer to string prefix for the mqtt publish topic *)
	pMqttPublishQueue := ADR(MqttVariables.fbMqttPublishQueue)      (* pointer to MqttPublishQueue to send a new Mqtt event *)
);

The MQTT publish topic in this code example will be Devices/PLC/House/Out/RS485/FB_RS485_EASTRON_SDM_POWER_001 (MQTTPubSwitchPrefix variable + function block name).

  • Registering device to a buscontroller (called once during startup):
RS485BusController.RegisterDevice(device := FB_RS485_EASTRON_SDM_POWER_001);

Home Assistant YAML

To integrate with Home Assistant use the YAML code below in your MQTT sensors config:

mqtt:
  sensor:
  - name: "car charger power"
    object_id: "car_charger_power"
    state_topic: "Devices/PLC/House/Out/RS485/FB_RS485_EASTRON_SDM_POWER_001/ACTP"
    unit_of_measurement: "W"
    device_class: "power"
    state_class: "measurement"
    qos: 2
    availability:
      - topic: "Devices/PLC/House/Out/RS485/FB_RS485_EASTRON_SDM_POWER_001/availability"
      - topic: "Devices/PLC/House/availability"
    availability_mode : "all"
    payload_available: "online"
    payload_not_available: "offline"

In addition to the above a Riemann sum integral integration can be added to calculate the energy (kWh) from the power (W):

- platform: integration
  source: sensor.car_charger_power
  name: "car charger energy"
  unit_prefix: k
  round: 3