Control Unit - Turning On or Off a Relay with an Action in iMonnit Online

The basic operation to engage/disengage a Control Unit’s Relays is facilitated by Actions in iMonnit. Actions can be triggered by a sensor reading, sensor Aware State, or other conditions. This article will demonstrate the basic configuration of an Action to trigger a Control Unit’s Relay.

Example

In this example, we will use a Control Unit’s relay 1 to engage a fan to bring in outdoor air into a building when the temperature reading from a Monnit temperature sensor reaches 82°F. A second Action will be configured to trigger the relay to go off once the Monnit temperature sensor reading reaches 75°F.

Physical Configuration: The fan has a two wire connection to power. The common wire connected the power source is spliced and connected to the two relay contacts; the relay interrupts the Common Wire connection between the fan and power source. The power source is set to the on position, but so long as the Relay is not engaged, the fan will not get power. The Relay must be engaged (completing the circuit by connecting the common wire between the fan and power source) to power the fan.
Conditions to engage: Sensor reading of greater than 80°F to Trigger the Control Unit’s Relay 1 On; sensor reading of less than 75°F to turn the Relay 1 Off.

Assuming the sensor and Control Unit are already communicating with the iMonnit Online Portal through a supported gateway, we need only to create the appropriate Action to trigger the relay. The following configurations are assumed.

  • Ethernet Gateway checking in with a 5 minute Heartbeat
  • Ethernet Gateway configured with a 1 minute Poll Interval
  • Sensor checking in with a 20 minute Heartbeat
  • Control Unit checking in with a 10 minute Heartbeat
  • Control Unit checking in with a 1 minute Poll Interval

Steps to configure the Actions

Engaging Relay 1 with a reading of 80°F

  • Create a new Action
  • Select Sensor Reading for the Action Type
  • Select Temperature Sensor (you will not select Control for your Trigger)
  • Select Greater than for the Action Trigger Conditions
  • Enter 80°F
  • Save
  • Select Use Control Unit for the Select Actions step
  • Continue
  • Select the Control Unit arrow icon to engage the Relay command (it will turn green)
  • Select the Relay command icon to engage the desired Relay state
  • Select Continue
  • Select the Trigger Sensor
  • Select Save

Disengaging Relay 1 with a reading of 75°F

  • Create a second new Action
  • Select Sensor Reading for the Action Type
  • Select Temperature Sensor (you will not select Control for your Trigger)
  • Select Less than for the Action Trigger Conditions
  • Enter 75°F
  • Save
  • Select Use Control Unit for the Select Actions step
  • Continue
  • Select the Control Unit arrow icon to engage the Relay command (it will turn green)
  • Select the Relay command icon to engage the desired Relay state
  • Select Continue
  • Select the Trigger Sensor
  • Select Save

How this works

With the above configurations, the sensor will be reporting data every 20 minutes. Once a reading comes in of greater than 80°F, the Relay will be engaged within 2 minutes (1 minute gateway Poll Interval + 1 minute Control Unit Interval + transmission time). The Action will trigger, and the Control Command will be delivered to the gateway within 1 minute. The gateway will queue the command, and the Control Unit will receive the command upon polling the gateway ever 1 minute, and engage Relay 1 to turn the fan on.

Once the fan is on, the temperature sensor will continue to report readings ever 20 minutes. Once the fan cools the room to below 80°F, the first Action will be Disarmed/Rearmed so it is ready to trigger in the future once a temperature above 80°F is reported in the future.

It is common to assume that once the Action is Disarmed/Rearmed, a command to disengage the Control Unit Relay will occur. However, this does not happen. A separate Action to disengage the Relay must execute to turn it off. Therefore in this specific example, the Relay will stay engaged/on and the fan will continue to operate. The temperature will continue to drop. Since we configured the second Action to send an Off command once the temperature sensor reports 75°F, Relay 1 will be turned off and so will the fan.

With this configuration, the fan will be on if the temperature is above 80°F, and it will be off if the temperature is below 75°F.



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