Tunnel – Automatic activation of relay output depending on the value of an analog 0-10V probe.

Scenario details:

• It is necessary to control 1 relay to activate the pumping motor of a well
• An analog 0-10V level sensor is available. When the level is low, that is, when the sensor returns a value below 2V, the relay acting on the motor must be activated to pump water. When the sensor returns a value above 8V, the relay must be deactivated to stop pumping water.
• The relay status (on/off) must be sent via 4G/3G/2G to an MQTT broker every time a change occurs. It must also be possible to activate/deactivate the modem relay that controls the well motor at any time from the MQTT broker, that is, remotely. A drop in connectivity with the MQTT broker should not interfere with the behavior of the analog sensor input to the relay

Solution: MTX-Tunnel firmware + MTX-IOT-S [4-N]

Configuration example (config.txt file) for the indicated scenario:

Details:

• The MTX-IOT-S family modems have up to 8 digital outputs (from GPIO0 to GPIO7) and 1 integrated relay (GPIO8). In this example GPIO8, which is associated with the MTX-IOT-S modem relay, has been configured to enable / disable the motor relay
  The analog input ADC0 of the MTX-IOT-S modem must be configured to read voltage (do not forget to properly configure the microswitches to configure the ADC0 in voltage mode, you will find more information in the Annexes of this manual)
  By configuring the MQTT_defaultIOTopic parameter, the modem will report in that MQTT topic in real time any change in the input / output GPIOs. For this reason, each time the relay associated with GPI8 is activated / deactivated, the modem will send a JSON to said topic MQTT informing of the new status
  The sending format of these messages follows the JSON structure, shown in the following example:
  {
  “IMEI”:”354033091487838”,
  “TYPE”:”GPIO”,
  “TS”:” 2020-02-09T12:33:18Z”
  “ID”:”8”,
  “VALUE”:1,
  “DIR”:”INPUT”
  }

  Where:
  – IMEI: indicates the IMEI of the MTX modem
  – TYPE: indicates the type of frame. “GPIO” is for digital I / O frames
  – TS: Timestamp (unix format specified in MTX_TPFormat)
  – ID: indicates the index of the GPIO (0 = GPIO0, 1 = GPIO1 …, 7 = GPIO7)
  – VALUE: indicates the value of the input (0,1)
  – DIR: indicates the type of pin (INPUT / OUTPUT)
  The configuration of ADC0 input as at;2000;8000;0;AT^MTXTUNNEL=SETIO,8,1; AT^MTXTUNNEL=SETIO,8,0;AT does:
  at: sets the analog input to at, which will cause specific AT commands to be executed when the analog value is above or below a certain threshold
  2000: minimum value (in mV) to execute low voltage AT commands
  8000: maximum value (in mV) to execute the high voltage AT commands
  0: hysteresis (in mV). In this example you don’t need
  AT ^ MTXTUNNEL = SETIO, 8.1: the AT command that is executed when the analog input value is below 2000 mV (i.e. the AT command that activates the GPIO8 output (the relay) to activate the motor)
  AT ^ MTXTUNNEL = SETIO, 8.0: the AT command that is executed when the analog input value is above 8000 mV (that is, the AT command that disables the GPIO8 output (the relay) to stop the motor)
  AT: the AT command that is executed when the sensor value is in the normal zone (that is, between 2000mV and 8000mV). In this example it is not used
  To remotely change the state of the GPIO8 (the relay), simply send the command AT ^ MTXTUNNEL = SETIO, 8.1 (to activate the relay) and AT ^ MTXTUNNEL = SETIO, 8.0 (to deactivate the relay) from the MQTT platform. ). AT commands must be sent to the TOPIC MQTT configured in the MQTT_attopic1 parameter and the modem will send the responses to the AT commands to the TOPIC MQTT MQTT_atrtopic
  Below is an example of sending the command: