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Create and Clear Alarms

Use case

Let’s assume your device is using DHT22 sensor to collect and push temperature readings to ThingsBoard. DHT22 sensor is good for -40 to 80°C temperature readings. We want generate Alarms if temperature is out of good range.

In this tutorial we will configure ThingsBoard Rule Engine to

Prerequisites

We assume you have completed the following guides and reviewed the articles listed below:

Adding the device

Add Device entity in ThingsBoard. Its name is Thermostat Home and its type is Thermostat.

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Message flow

In this section, we explain the purpose of each node in this tutorial:


Configure Rule Chains

In this tutorial, we modified our Root Rule Chain and also created Rule Chain Create & Clear Alarms


The following screenshots show how the above Rule Chains should look like:

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Download the attached json file for the Create & Clear Alarms rule chain. Create Node D as shown on the image above in the root rule chain to forward telemetry to the imported rule chain.

The following section shows you how to create this rule chain from scratch.

Create new Rule Chain (Create & Clear Alarms)

Go to Rule Chains -> Add new Rule Chain

Configuration:

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New Rule Chain is created. Press Edit button and configure Chain.

Adding the required nodes

In this rule chain, you will create 3 nodes as it will be explained in the following sections:

Node A: Filter Script
return msg.temperature < -40 || msg.temperature > 80;

If the temperature is in the expected interval the script will return False, otherwise True will be returned.

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Node B: Create alarm

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Node C: Clear Alarm

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Modify Root Rule Chain

The following screenshot shows the initial Root Rule Chain.

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The initial Rule Chain has been modified by adding the following node:

Node D: Rule Chain

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The following screenshot shows how the final Root Rule Chain should look like:

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How to verify the Rule Chain and Post telemetry

For posting device telemetry we will use the Rest APIs, Telemetry upload APIs. For this we will need to copy device access token from then device Thermostat Home.

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**you need to replace $ACCESS_TOKEN with actual device token**

Let’s pushed debug mode button in Clear Alarm and Create Alarm node to verify the results.

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sent temperature = 99. Alarm should be created:

curl -v -X POST -d '{"temperature":99}' http://localhost:8080/api/v1/$ACCESS_TOKEN/telemetry --header "Content-Type:application/json"

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Lets post temperature = 180. Alarm should be updated:

curl -v -X POST -d '{"temperature":180}' http://localhost:8080/api/v1/$ACCESS_TOKEN/telemetry --header "Content-Type:application/json"

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Lets post temperature = 30. Alarm should be cleared:

curl -v -X POST -d '{"temperature":30}' http://localhost:8080/api/v1/$ACCESS_TOKEN/telemetry --header "Content-Type:application/json"

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Also, you can:

Please refer to the links from the second to the fourth under the See Also section to see how to do this.


See Also