Turning On or Off a Control Unit Relay with an iMonnit Rule
You can engage/disengage an ALTA Control Unit’s two relays with Rules in iMonnit. Rules can be triggered by a sensor reading, Aware State, on schedule, or other conditions. This article will show you how to configure a Rule to trigger a Control Unit’s relays.
Example
In this example, we use an ALTA Control Unit’s Relay 1 to engage a fan to bring air into a building when the temperature reading from an ALTA Temperature Sensor reaches 82°F. We'll configure a second Rule to trigger the relay to go off once the temperature sensor's reading reaches 75°F.
Physical configuration: The fan has a two-wire connection to power. We splice the common wire that connects the power source and connect it to the two relay contacts; the relay interrupts the common wire connection between the fan and the power source. We set the power source to on, but the fan won't get power if the relay is not engaged. 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: A sensor reading of greater than 80°F to trigger the control unit’s Relay 1 On; a sensor reading of less than 75°F to turn Relay 1 Off.
Assuming the sensor and control unit are already communicating with iMonnit through a supported gateway, we can create the appropriate Rule to trigger the relay. The following configurations are assumed.
- ALTA Ethernet Gateway checking in with a 5-minute Heartbeat
- ALTA 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 Rules
Engaging Relay 1 with a Reading of 80°F
- Create a new Rule.
- Select Sensor Reading for the Rule Type.
- Select the desired Temperature Sensor in the Pick A Device step (you will not select the Control Unit for your trigger).
- Select Greater than for the Condition.
- Enter 80°F.
- Select Save.
- Select Use Control Unit for the When Condition is Met step.
- Select Continue.
- Select the + button icon to engage the Relay Command (it will turn green).
- Select the Send command to turn Relay 1 toggle to engage the desired relay state.
- Engage the Set Command Timer toggle to engage the relay command for a specific amount of time.
- Select Save.
- Select the I’m done adding tasks button.
- Enter a Name for the Rule.
- Select Save.
Disengaging Relay 1 with a Reading of 75°F
- Create a second new Rule.
- Select Sensor Reading for the Rule Type.
- Select the desired Temperature Sensor in the Pick A Device step (you will not select the Control Unit for your trigger).
- Select Less Than for the Condition.
- Enter 75°F.
- Select Save.
- Select Use Control Unit for the When Condition is Met step.
- Select Continue.
- Select the + button icon to engage the Relay Command (it will turn green).
- Select the Send command to turn Relay 1 toggle to engage the desired relay state (in this case, the toggle should be set to off).
- Engage the Set Command Timer toggle to engage the relay command for a specific amount of time.
- Select Save.
- Select the I’m done adding tasks button.
- Enter a Name for the Rule.
- Select Save.
How This Works
With the above configurations, the sensor will be reporting data every 20 minutes.
Once a reading of greater than 80°F occurs, the relay engages within two minutes (1-minute gateway Poll Interval + 1-minute control unit Poll Interval + transmission time).
The Rule will trigger, and the control command will be delivered to the gateway within one minute.
The gateway will queue the command.
The control unit will receive the command upon polling the gateway every minute and engage Relay 1 to turn on the fan.
Once the fan is on, the temperature sensor will continue to report readings every 20 minutes.
Once the fan cools the room to below 80°F, the first Rule will be Disarmed/Rearmed, so it is ready to trigger once a temperature above 80°F is reported.
It is common to assume that once the Rule is Disarmed/Rearmed, a command to disengage the control unit’s relay will occur. However, this does not happen. A separate Rule to disengage the relay must be executed 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 Rule 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 remain on until the temperature cools to 75°F). It will be off if the temperature is below 75°F (and remain off until the temperature heats to 80°F).