Node-RED Tutorial: Node-RED Example Project
Use an open source Raspberry Pi PLC or Panel PC and automate your application using a Node-RED Dashboard
23 December, 2021 by
Node-RED Tutorial: Node-RED Example Project
Boot & Work Corp. S.L., Fernandez Queralt Martinez

Introduction

Do you have or work in a small / medium-sized company and you keep wasting time doing processes manually? Do you know that, thanks to industrial automation, you can automate them and invest your time in another tasks?

In this post, we are going to show you how to automate these processes that you were still doing manually. We will activate and deactivate an output, analog or digital, with customizable time from the Node-RED Dashboard, and this application will work only if a digital input is at 1.

Do you want to know how? 

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Requirements

  • Some valve, sensor > or actuator to connect to the input and output

Node-RED

We will create our application with Node-RED >, so the first thing to do is download and install it, either as an application or as a service.

By default on your open source Raspberry Pi PLC or Panel PC, Node-RED comes by default. If you don't have it, please download it by clicking on this link > .

Node-RED example Dashboard - Node-RED Tutorial: Node-RED Example Project

Application example

To make this post really useful, we are going to see some practical examples in which you can use the Node-RED flows and control your application through the Node-RED Dashboard.

First of all, we invite you to take a look at this post, where you can see a list of up to 50 industrial applications! >

Now, we are going to see how to take advantage of this example Node-RED flows.json that we provide you to be able to control your application through a Dashboard.

1. In the first place, we could connect a digital input signal such as a frequency inverter, which if it is turned on, will activate an ON/OFF valve that will regulate the emission of liquids inside bottles for the time that we tell it. The on time will be the time that the valve will let liquid pass through, and the off time will be the time that it will not let it pass. Liquid will be emitted intermittently. The same application can be applicable to a labeling system > and as many projects as you can think about.

This applications would be an example for an automatic input.

Automatic input - Application example - Node-RED Tutorial: Node-RED Example Project

2. Another application could be to receive the signal from a switch, and when we receive a HIGH signal, therefore, when the switch is on, activate the intermittent output, like a light, alarm, valve, pump, motor, turbine, etc.

This example would be applicable as a manually triggered input

Manually Triggered input - Application example - Node-RED Tutorial: Node-RED Example Project

Node-RED flows.json

Once Node-RED is correctly installed, go to the the menu > click on Import > copy this flows.json:

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And paste it to the import nodes (clipboard).

Explanation

Explanation - Node-RED Tutorial: Node-RED Example Project

Once imported, you should see your flows.json, something like the picture above, which is divided into several parts:

1. We create a file called /home/pi/values.json that will serve as a database of the stored values, so that when the application is stopped and turned on again, the values are initialized with the last ones established.

2. We initialize the variables of T1, T2, active and useInput, we assign these values in flow variables.

3. With the flow variables, we will assign the value of another variable in the execution flow.

4. If the digital input signal is at 1 and also the enable switch is activated, running must be positive. And if in addition, the force button is also activated, the application has to run.

If, on the contrary, the digital input signal is deactivated but the force is activated, the application also has to work, as long as the activate button is lit, otherwise the output must be deactivated.

5. Finally, there is a template node where you can modify the CSS from the  Node-RED Dashboard. 

Once the entire application has taken its logic. You can change the nodes of write digital output  or  read digital input for analog in case your inputs or outputs are analog, as well as the appearance and so.


Finally, go to your Dashboard and enjoy your application!

Dashboard - Node-RED Tutorial: Node-RED Example Project
Node-RED Tutorial: Node-RED Example Project
Boot & Work Corp. S.L., Fernandez Queralt Martinez
23 December, 2021
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