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. We will configure two rules in the example.
Example
We'll create a Rule for 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 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 disengaged. To power the fan, the relay must be engaged, completing the circuit by connecting the common wire between the fan and power source.
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.
The sensor and control unit communicate with iMonnit through a supported gateway, so we can create the appropriate Rule to trigger the relay. We've also already made the following configurations.
- ALTA Ethernet Gateway checking in with a 5-minute Heartbeat
- ALTA Ethernet Gateway configured with a 1-minute Poll Interval
- ALTA 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
Example Rule 1: Engaging Relay 1 with a Reading of 80°F
- Select Rules and click +Create New Rule (Create a new Rule.)
- In Create a Rule select Sensor Reading in the Choose the Rule Type data box.
- 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. (See Image below)
- In Step 4: Set Up Tasks: Select Command Control Unit for the When Condition is Met step.
- Select Done adding tasks (See image below)
- 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. (See image below)
- Select the Done adding tasks button.
- Enter a Name for the Rule.
- Select Save.
Example Rule 2: Disengaging Relay 1 with a Reading of 75°F
- Select Rules and click +Create New Rule (Create a new Rule.)
- In Create a Rule select Sensor Reading in the Choose the Rule Type data box.
- 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.
- In Step 4: Set Up Tasks: Select Command Control Unit for the When Condition is Met step.
- Select Done adding tasks (See image below)
- 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. (See image below)
- Select the Done adding tasks button.
- Enter a Name for the Rule.
- Select Save.
How This Works
- With the above configurations, the sensor will report data every 20 minutes.
- Once a reading 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.
- After polling the gateway every minute, the control unit receives the command and engages 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 stay off until the temperature heats to 80°F).