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Apology to your teacher

Introduction​

Even a mobile phone isn't perfect! Sometimes it lets you down and doesn't wake you up. When that happens, don't panic. Press 👇 the smart button and apologize to your teacher before they tell your parents.

In this project, you will learn how to send a notification with a smart button. 📩

All you need is the basic HARDWARIO Start Set.

Make it happen in Node-RED​

  1. Assemble the Start Set and pair it. The Core Module needs the twr-radio-push-button firmware. If you're doing this for the first time, or you're not sure what firmware is and how to upload it, we've prepared a simple guide.
  2. In Playground, click the Functions tab, where you'll find the Node-RED programming workspace. 🤖
  3. From the palette on the left, drag the mqtt in node from the network section onto the Node-RED workspace.
Node-RED palette with the mqtt in node highlighted and an mqtt node placed on the flow canvas
  1. Set up the key function in the node: the button press. Double-click the node to open its settings and copy this line into the Topic field:
node/push-button:0/push-button/-/event-count

Confirm with Done.

Write your apology​

  1. You write the apology in Node-RED too. Next to the MQTT node, place a change node from the function section. It decides which message gets sent.
Change node highlighted in the palette, with a set msg.payload node placed next to the push-button MQTT node
  1. Double-click the node and set a rule for msg.payload in the Rules field (see the screenshot below). This is the text of your message. Keep in mind that the notification can't show accented letters such as č or á, and don't forget to sign it. Your message could read like this:

Dear Mr. Woodpecker, I'm sorry, but my dog ate my alarm clock. I'll be there as soon as I can. Evzen (your favorite pupil, who doesn't deserve a note home).

Edit change node dialog with Rules setting msg.payload to the apology message text

Confirm with Done. 👏

Prepare Blynk IoT for notifications​

The apology reaches your teacher's phone as a push notification from the Blynk IoT app. 📱 Node-RED sends the text to Blynk, and a Blynk automation turns every new message into a notification.

  1. If you don't have a Blynk IoT account yet, create one. The free plan is enough for this project: at the time of writing, it includes push notifications in the app and up to five automations.

  2. Create a device template. Blynk's quick guide shows you how. You can also reuse a template from an earlier project.

  3. In the template, open the Datastreams tab, click New Datastream and choose Virtual Pin. Name the datastream (for example Message), pick a free pin (for example V2) and set the Data Type to String, because the notification will carry your own text.

  4. In the datastream settings, let automations use it as a trigger: in the Automations section, turn on Use as Condition. Create the datastream and save the template.

  5. Create a device from the template: in Devices, add a new device, choose your template and give the device a name. You'll find its Auth Token on the device's Device Info tab. You'll need it in Node-RED.

Create the automation​

  1. Open Automations in Blynk and create a new automation. For the condition (When), choose Device State, then your device, your datastream and Is Any. The automation will then react to every message, even when it's the same as the last one.

  2. Under Do this, add the action that sends a notification to the mobile app (Send In-App Notifications) and choose yourself as the recipient. Put the Trigger value placeholder ({TRIGGER_VALUE}) in the message. Blynk replaces it with the text that Node-RED sends.

  3. Name the automation. Limit period sets how soon the automation may run again: choose the shortest option, otherwise a second message sent soon after the first won't arrive. Save the automation.

  4. Download the Blynk IoT app to your phone from the App Store or Google Play and sign in with the same account. Make sure the app is allowed to show notifications, so the apology can pop up. ✉️

Set up sending the apology​

  1. Go back to Playground. On the Node-RED workspace, add the write node from the Blynk IoT section after the change node with your apology. Leave the Blynk ws section alone: it belongs to the old Blynk, which no longer works. 📮

  2. Double-click the node to open it. Next to Connection you'll see a small pencil. Click it to open a new window. In the Url field enter blynk.cloud, and copy the Auth Token and Template ID from the Blynk web app on your computer: the Auth Token is on the device's Device Info tab, the Template ID in the template details. Confirm with Add.

  3. In the Virtual Pin field, enter the number of your datastream's pin (2 for V2). This is what turns the button press into a push notification: the node writes the apology to the datastream, and the automation sends it on. Confirm with Done.

  4. Connect the nodes so the button press ➡️ turns into your apology, ➡️ which goes to Blynk IoT ➡️ and lands on your teacher's phone. Then press Deploy and relax: the apology that will save your skin when you're late is ready! 🙏

Ready, steady… go!​

  1. Want to try it out? Test it with your own account, so the notification lands on your own phone.
  2. Press Deploy again, then press the button and… hey presto, someone has just got your message! 💌