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Safe drawer

Introduction​

Do you keep a diary, poems or a top-secret government document in your drawer? If nobody should see it, protect it. πŸ”’ Turn your Start Set into an IoT drawer guard that sends alerts to your phone. πŸ“²

In this project, you will learn to build a drawer detector that alerts your phone when someone opens the drawer. πŸ‘ˆ

You only need a box with a button and a Radio Dongle, so the basic HARDWARIO Start Set is all you need.

Download the new firmware​

  1. Flash the special twr-radio-move-detector-x-axis firmware to the Core Module (you'll find it among the other firmware in Playground). It makes the box more sensitive to movement. πŸ‘Œ

Our tip: Don't know how to get the firmware or what it is? Find out here.

  1. Pair the Core Module with the Radio Dongle. Right after pairing, you'll see the Core Module's alias change to x-axis-detector.
Playground Devices tab: the paired device row with alias x-axis-detector:0 highlighted

Prepare the Blynk IoT app​

Your box reports to your phone through the Blynk IoT app. πŸ“± You'll set up two things there: a switch that turns the detector on and off, and a push notification that arrives when someone opens the drawer. Node-RED sends the text of the alert 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. Add a datastream for the message. In the template, open the Datastreams tab, click Edit in the top right, then 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. In the datastream settings, let automations use it as a trigger: in the Automations section, turn on Use as Condition. Create the datastream.

  4. Add a datastream for the detector state. Add one more Virtual Pin datastream (for example Detector on V3) and choose the Integer type with a range of 0–1 (0 = off, 1 = on). Click Create and save the template with Save.

  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, the message 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 notifications are allowed for the app so the alert can pop up. πŸ“±

  5. On your phone, open the device and set up its dashboard: add a Button widget, switch it to Switch mode and assign it the detector-state datastream. Now you can turn the detector on and off from your phone whenever you like.

Set up the message in Node-RED​

  1. In Playground, click the Functions tab, home of the Node-RED programming canvas.

  2. Start as always: first place an mqtt in node from the network section on the canvas.

Double-click it and copy this topic into the Topic field. The box uses it to report movement:

node/x-axis-detector:0/accelerometer/-/event-count
Edit mqtt in node dialog with the accelerometer event-count topic in the highlighted Topic field
  1. Next to this node, place a Switch node from the Function section. With it, you can turn detection off when you're home and opening the drawer yourself.
Node-RED workspace with a Switch node placed next to the x-axis-detector MQTT node
  1. In the node, change the Property field to flow.active and enter the number 1 in the field below it. Thanks to the 1, the notification goes out only when the switch is on; otherwise it's dropped. Follow the screenshot.
Edit switch node dialog: Property set to flow.active with rule equals 1
  1. After it, place a Change node from the Function section.
Node-RED workspace with a Change node (set msg.payload) added after the Switch node
  1. In it, set the message you'll get on your phone. Careful: Blynk can't handle accented letters. 🀷
Edit change node dialog: msg.payload set to the alert message text

  1. At the end of this food chain, place the write node from the Blynk IoT section. Leave the Blynk ws section alone: it belongs to the old Blynk, which no longer works.

  2. Double-click it to open its settings. Next to Connection you'll see a small pencil. Click it and a new window opens. 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.

Our tip: Name the connection so you'll easily recognize it in other nodes.

  1. In the Virtual Pin field, enter the number of the message datastream's pin (2 for V2). That turns opening the drawer into a push notification: the node writes the message to the datastream, and the automation sends it on. Confirm with Done.

  2. Now wire up the whole chain: MQTT ➑️ Switch ➑️ Change ➑️ Blynk IoT write. On we go.

Set up the detector switch in Node-RED​

The second chain reads the Switch widget on your phone, so you can turn the detector on and off remotely.

  1. Start another chain: place a write event node from the Blynk IoT section on the canvas. It receives the switch state from your phone.

  2. Double-click it to open it. In the Connection field, select the connection you set up above in the write node. In the Virtual Pin field, enter the pin number of the detector-state datastream (3 for V3). Confirm with Done.

  3. And the last node joins the party: place a Change node from the Function section on the canvas.

  4. Set the node up to react when you turn the switch on or off in Blynk. Double-click it and enter flow.active and msg.payload in the Rules fields, so the switch value is stored in the flow.active variable, which the Switch node in the first chain checks.

  5. Now wire these two together. Don't forget to click the Deploy button in the top right, too, so everything starts.

Set the trap​

  1. Lay the box flat in the drawer.

  2. You control everything else from your phone. πŸ“± Open the device in the Blynk IoT app and turn on the detector by flipping the Switch widget to ON. (If it's already on from earlier, switch it off and on again, so Node-RED learns its state.)

  3. And wait for the mouse to take the bait. πŸ₯ As soon as someone opens the drawer, a push notification pops up on your phone. Meanwhile, plan what to do with the sneaky intruder. We suggest making them do your chores for a week. They deserve it.